Method for increasing the ultrasonic burst length depending on the distance

Abstract

Method for transmitting an ultrasonic burst for use in ultrasonic sensor systems in vehicles, comprising the steps - Step 1: Emission of an ultrasonic burst with an ultrasonic burst duration (bd) not exceeding a maximum ultrasonic burst duration (bd) by an ultrasonic sensor system (USS); - Step 2: Receiving an ultrasonic burst reflected by an object (O); - Step 3: Determining the distance (D) between the ultrasonic sensor system (USS) and the object (O) as a function of the received reflected ultrasonic burst; - Step 4: Repeating steps 1 to 4, wherein the ultrasonic burst duration (bd) depends on the determined distance (D, s1, s2). - that the ultrasonic burst length of the ultrasonic burst duration (bd) is increased by the fourth root of the determined distance (D).

Description

Field of the InventionThe invention is directed to a method of emitting an ultrasonic burst for use in vehicle ultrasonic sensor systems.General IntroductionIn the context of autonomous driving, ever better measuring devices are required for elucidating the vehicle environment. In this case, the bandwidth of the ultrasonic signals which can be transmitted and received is set to distinct limits, since the ultrasonic transducers used have a strong resonance of high quality and thus a low bandwidth.It is therefore necessary to optimize the profile of the modulation frequency within a chirp signal.In this context, we point to WO 2010 / 063 510 A1. WO 2010 / 063 510 A1 describes a detection device and a method for detecting the surroundings of a vehicle. WO 2010 / 063 510 A1 uses signals of interest in particular in connection with the use of ultrasound in vehicles.EP 1 231 481 A2 discloses a method for operating an ultrasonic multisensor array which does not address the bandwidth problem.U.S. Pat. No. 7,693,007 B2 discloses an ultrasonic sensor with a separate ultrasonic transmitter and ultrasonic receiver.DE 10 2008 002 232 A1 discloses a method and apparatus for determining the distance and / or speed of an object relative to a vehicle. DE 10 2008 002 232 A1 does not address the bandwidth problem.DE 101 45 292 A1 discloses a method for distance measurement by means of ultrasound. DE 101 45 292 A1 does not address the bandwidth problem.From JP S58-50 484 A a guiding device for driving a motor vehicle backwards by means of ultrasound is known. JP S58-50 484 A does not address the bandwidth problem.None of the references presented solves or contributes to such a solution.The object is to provide a method for performing a processThe object of the proposal is therefore to provide a solution which does not have the above disadvantages of the prior art and has further advantages.This object is achieved by a proposal according to the claims. More specifically, its solution is supported by the proposal according to the claims. Further refinements are the subject matter of the dependent claims.Solution of the ProblemThe invention relates to a method for transmitting an ultrasonic burst for use in ultrasonic sensor systems in vehicles. The method comprises the steps: 1. step 1: emitting an ultrasonic burst with an ultrasonic burst duration (bd) that does not exceed a maximum ultrasonic burst duration (bd) by an ultrasonic sensor system (USS); 2. step 2: receiving an ultrasonic burst reflected by an object (O); 3. step 3: determining the distance (D) between the ultrasonic sensor system (USS) and the object (O) as a function of the received reflected ultrasonic burst; 4. step 4: repeating steps 1 to 4, wherein the ultrasonic burst duration (bd) depends on the determined distance (D, s1, s2).The method is characterized in that the ultrasonic burst length of the ultrasonic burst duration (bd) is increased with the fourth root of the determined distance (D) according to the formula bd=bd 1* D 1 / 4+ bd 0 with bd 0 and bd 1 as constants.One method for adapting the ultrasonic signals, more precisely the ultrasonic bursts (UB), to the object to be examined in the environment of a vehicle is the adaptation of the transmission amplitude and the transmission frequency when detecting an object as a function of object properties, such as distance and / or reflectivity. For this purpose, the reception amplitude is recorded by an ultrasonic measuring device, the ultrasonic sensor system (USS), by means of corresponding ultrasonic receivers and / or ultrasonic transducers (US 1, US 2, US 3) and compared with a setpoint reception amplitude profile. If the reception amplitude is too high at a point in time, the ultrasonic transducers are attenuated individually or jointly. The attenuation of one or more ultrasonic transducers is optionally preferably effected by connecting attenuation elements, for example by connecting resistors in parallel with the ultrasonic transducers (US 1, US 2, US 3). If the amplitude is too low, the relevant ultrasonic transducer is supplied with more vibration energy.Another method is to control the ultrasonic burst amplitude (A) with which the ultrasonic transducer (US1, US2, IS3) transmits. In this case, attempts are made to keep the reception amplitude of the echoes constant at the location of the relevant ultrasonic transducer or at the location of the ultrasonic sensor system (USS) which comprises a plurality of ultrasonic transducers (USS) when received by the ultrasonic transducer (US1, US2, US3). A central idea of this disclosure is the adaptation of ultrasonic burst properties to the previously recognized environment. In this case, it is ultimately irrelevant whether the detection was carried out by means of ultrasound or other methods such as radar and / or lidar and / or by means of image evaluation of camera images. Such an adaptation of an ultrasonic burst property for ultrasonic bursts to be transmitted can be, for example, an increase and / or decrease of the ultrasonic burst amplitude during the transmission of the ultrasonic burst depending on the distance of an object to be examined or detected. In an analogous manner, the ultrasonic burst torque frequency can also be increased or decreased when the ultrasonic burst is transmitted as a function of the distance of the object.A substantially hyperbolic profile of the ultrasonic burst torque frequency as a function of time within an ultrasonic burst is particularly preferred for improved Doppler robustness.For the detection of a small object, for example in the size of a moth, a sound pressure of 130 dB at a distance of 15 m is typically useful for a 10 ms ultrasonic burst duration and a 110 ms time interval between two successive ultrasonic bursts. High sound pressure, low frequency, long pulse duration and low pulse repetition frequency are important.When approaching an object identified as important in the vehicle environment, the tasks result• exact 3D localization• Structure Detection (Object Classification, Size, Sensitive Object Components (e.g. Certain Human Body Parts to be Protected))• Compensation of the Doppler EffectUltrasonic bursts in this phase:• Short at high repetition rate (80 to 90 ultrasonic bursts / second at approach),• up to 200 ultrasonic bursts / second in the vicinity of the object,• broadband transmission and reception of the ultrasonic bursts in order to obtain more spectral information,• linear or hyperbolically downward-pointing frequency modulation of the ultrasonic bursts,• Reduction of the ultrasonic burst amplitude in the vicinity of the object, preventing overdrives.In the approach phase to the object or to a group of objects, the sequence and shape of the ultrasonic bursts are preferably continuously changed during the approach: at a relatively long distance, the ultrasonic bursts are preferably provided with a large ultrasonic burst amplitude and with a relative low-frequency ultrasonic torque frequency and preferably narrowband. Preferably, frequency-modulated chirps with a higher starting frequency and a less-resonant, i.e. smaller, ultrasonic burst amplitude are used in the vicinity of the object or objects. For good processing, very rapid signal processing for high pulse repetition frequencies is expedient.A 3D localization possibility for objects is optionally obtained by means of a plurality of ultrasonic transducers which are placed suitably with respect to one another. If the ultrasonic transducers are very broadbanding, then for example 2 sensors can be placed next to one another in "ear spacing". In this document, an increase in the broadbandness by coupling a plurality of ultrasonic transducers to form an ultrasonic sensor system is proposed. A direction determination can be made in particular via transit time differences. The evaluation of such runtime differences can be carried out by means of a neural network. An evaluation of the relationship between height of the reflecting object and frequency content of the echo can likewise be effected via a neural network. One proposal, which will be further worked out below, comprises two ultrasonic transducers placed close together. One of these two ultrasound transducers should be provided with a low resonant frequency and the other of the two ultrasound transducers should be provided with a high resonant frequency, which are activated at different distance ranges from the object for emitting the ultrasound bursts.A vehicle moving towards an object must compensate for two Doppler errors: a. distance error: overestimate of the distance to the object, b. accuracy error: the object can no longer be localized as precisely (widening of the CCF curve)Compensation is necessary for this: 1. both errors are reduced if the bandwidth is increased with the ultrasound burst duration remaining the same, or if the bandwidth remains the same, the ultrasound burst duration is reduced. 2. since the vehicle generally moves towards the object of interest, this leads to an underestimate of the distance on the basis of runtime determinations. This can compensate for the overestimate due to the Doppler effect at a specific distance from the object. The ultrasonic burst is therefore continuously adapted accordingly according to the proposal so that the compensated distance corresponds to the real distance. Preferably, a neural network is used for this purpose. This neural network preferably regulates one or more ultrasonic burst parameters of one or more time-subsequent ultrasonic bursts on the basis of signals derived from the received ultrasonic signals. 3. a complete compensation of the accuracy error takes place only in the case of a strictly hyperbolic frequency modulation of the ultrasonic burst instantaneous frequency during the ultrasonic burst as a function of time (t).In principle, a short ultrasonic burst duration at a high bandwidth is thus desirable in order to obtain a maximum of information. By training a neural network for adapting the ultrasonic burst properties of the ultrasonic bursts to be transmitted in the future, this neural network can be used for determining and setting these ultrasonic burst properties before the transmission of an ultrasonic burst. The aim here is the optimum ultrasound burst adaptation for variable compensating distance.For structure detection and / or object classification, it is expedient to evaluate the fine structure of the echoes of the ultrasonic bursts. This makes use of the fact that each part of an object, for example a pedestrian, reflects the ultrasonic burst at slightly different times. From the resulting temporal fine structure of the echo, a "depth profile" of the object can then be created. At the same time, spectral differences also result, because of the different reflection / absorption behavior of different materials of the different surfaces of the object.As in 3D localization, differences between the received signals at multiple ultrasonic sensor systems having multiple ultrasonic transducers are also evaluated for this purpose. Preferably, the environment of the ultrasonic sensor system, for example the type of mounting or the structure of the surfaces in the environment of the ultrasonic sensor system and other components add further frequency filtering, on the distance of which the neural network used for the evaluation must be trained.A further method relates to a method for emitting an ultrasonic signal by means of an ultrasonic sensor system (USS). The ultrasonic signal has an ultrasonic burst (UB), wherein the ultrasonic burst has at least two, but typically considerably more, ultrasonic pulses (P 0 to P 7). Each of the at least two ultrasonic pulses (P 0 to P 7) has a temporal ultrasonic pulse start and a temporal ultrasonic pulse end. In this case, for example, the intersection point of the burst-like fluctuating sound pressure during the ultrasonic burst with the 50% sound pressure amplitude with respect to the maximum sound pressure occurring during an ultrasonic pulse can be used for determining the ultrasonic pulse start and the ultrasonic pulse end. The ultrasonic period (T 1 to T 7) of an individual ultrasonic pulse (P 0 to P 7) is, for the purposes of this specification, the time from the temporal ultrasonic pulse end of the immediately preceding temporal ultrasonic pulse to the temporal ultrasonic pulse end of the relevant ultrasonic pulse. These definitions are chosen in such a way that an ultrasonic torque frequency (f m) can be determined in the time of the ultrasonic pulse. In the broadest sense, an ultrasonic pulse in the sense of this document is therefore a wavelet whose stretching factor can be varied during the duration of the ultrasonic pulse. In this respect, therefore, in the sense of this document any type of time-limited wavelet with a time-limited wavelet duration is encompassed by the term ultrasonic pulse. The wavelet duration corresponds to the ultrasonic pulse duration (dh) of the ultrasonic period (T 1 to T 7). The respective ultrasonic torque frequency (f m1 to f m7) is the reciprocal of the respective ultrasonic period (T 1 to T 7) of the respective ultrasonic pulse (P 0 to P 7). The rate of change (v f) of the ultrasonic instantaneous frequency (f m) is thus the first derivative of the ultrasonic instantaneous frequency (f m) with time (t). The ultrasonic burst (UB) begins at an ultrasonic burst beginning (UBS) which is equal to the ultrasonic pulse beginning of the first pulse (P 0) of the ultrasonic burst (UB). The ultrasonic burst (UB) ends at an ultrasonic burst end (UBE) which is equal to the ultrasonic pulse end of the last pulse (P 7) of the ultrasonic burst (UB). The ultrasonic burst (UB) has a burst duration (BD), which is the value of the time difference between the ultrasonic burst start (UBS) and the ultrasonic burst end (UBE). In this disclosure, it is now proposed that the ultrasonic burst (UB) can be divided in time into a first burst phase (t 1a) and a second burst phase (t 1b) by a first half-frequency time (t 1 / 50%). In this case, the first half-frequency time (t 1 / 50%) is the time within the transmission time of an ultrasonic burst (UB) at which the ultrasonic torque frequency (f m) corresponds to the first upper half-maximum amplitude frequency (f 1o) or to the first lower half-maximum amplitude frequency (f 1u). At the first upper half maximum amplitude frequency (f 1o) the amplitude (A) of the sound radiation of the first ultrasound transducer (US1) is half of the first amplitude maximum (A max1) of the sound radiation of the first ultrasound transducer (US1) at its first resonant frequency (f 1). The first upper half maximum amplitude frequency (f 1o) of the first ultrasound transducer (US1) is above the first resonant frequency (f 1) of the first ultrasound transducer (US1) in terms of amount. At the first lower half maximum amplitude frequency (f 1u) the amplitude (A) of the sound radiation of the first ultrasound transducer (US1) is likewise half of the first amplitude maximum (A max1) of the sound radiation of the first ultrasound transducer (US1) at its first resonant frequency (f 1). The first lower half maximum amplitude frequency (f 1u) of the first ultrasound transducer (US1) is below the first resonant frequency (f 1) of the first ultrasound transducer (US1) in terms of amount.This method is characterized in that the magnitude of the average rate of change (v f) of the ultrasonic torque incident frequency (f m) in the first burst phase (t 1a) deviates from the magnitude of the average rate of change (v f) of the ultrasonic torque incident frequency (f m) in the second burst phase (t 1b) preferably by more than 10% and / or better by more than 20% and / or better by more than 50% and / or better by more than 100%.The first burst phase (t 1a) preferably has a time length which deviates from the time length of the second burst phase (t 1b) by more than 10% and / or by more than 20% by more than 50% by more than 100%.Likewise preferably, the time length of the first burst phase (t 1a) is more than 10% and / or more than 20% more than 50% more than 75% shorter than the time length of the second burst phase (t 1b).According to the proposal, this method can be carried out simultaneously at a plurality of ultrasonic torque frequencies (f m1, f m2) which provides additional information about the objects possibly located in the environment of the vehicle. This is then a method for transmitting an ultrasonic signal, wherein the ultrasonic signal has an overall ultrasonic burst (UB), and wherein the overall ultrasonic burst (UB) comprises a first partial ultrasonic burst, and wherein the overall ultrasonic burst (UB) comprises a second partial ultrasonic burst. Each ultrasonic subburst of the ultrasonic subbursts has at least two, typically substantially more, ultrasonic pulses (P 0 to P 7). Each of the at least two ultrasonic pulses (P 0 to P 7) of an ultrasonic subburst again has a temporal ultrasonic pulse start and a temporal ultrasonic pulse end. The ultrasonic period (T 1 to T 7) of an individual ultrasonic pulse (P 0 to P 7) of an ultrasonic subburst, hereinafter referred to as the relevant ultrasonic pulse, is again the time from the temporal ultrasonic pulse end of the ultrasonic pulse immediately preceding the relevant ultrasonic pulse in time to the temporal ultrasonic pulse end of the relevant ultrasonic pulse. The first ultrasonic instantaneous frequency (f 1m) of the first ultrasonic subburst is the reciprocal of the instantaneous ultrasonic period (T 1m) of the first ultrasonic subburst. The second ultrasonic instantaneous frequency (f 2m) of the second ultrasonic subburst is the reciprocal of the instantaneous ultrasonic period (T 2m) of the second ultrasonic subburst. The first ultrasound subburst begins at a first start time (t 1s), which is equal to the ultrasound pulse start of the first ultrasound pulse (P 0) of the first ultrasound subburst. The first ultrasound subburst ends at a first end time (t 1e), which is equal to the ultrasound pulse end of the last ultrasound pulse (P7) of the first ultrasound subburst. The first ultrasound subburst has a first ultrasound subburst duration (t 1e- t 1s which is the value of the time difference between the first end time (t 1e) minus the first start time (t 1s). The second ultrasound subburst begins at a second start time (t 2s), which is equal to the ultrasound pulse start of the first ultrasound pulse (P 0) of the second ultrasound subburst. The second ultrasound subburst ends at a second end time (t 2e), which is equal to the ultrasound pulse end of the last ultrasound pulse (P7) of the second ultrasound subburst. The second ultrasound subburst has a second ultrasound subburst duration (t 2e- t 2s) which is the value of the time difference between the second end time (t 2e) minus the second start time (t 2s). This method variant is characterized in that the first ultrasonic torque frequency (f 1m) is different from the second ultrasonic torque frequency (f 2m) at at least one time between the first starting time (t 1s) and the first ending time (t 1e) and simultaneously between the second starting time (t 2s) and the second ending time (t 2e). Thus, two ultrasonic instantaneous frequencies (fm1, fm2) are always transmitted by the ultrasonic sensor system (USS).A first method variant provides that the second start time (t 2s) lies temporally between the first start time (t 1s) and the first end time (t 1e) and / or that the second start time (t 2s) is equal to the first start time (t 1s).In another variant, the second end time (t 2e) lies temporally between the first start time (t 1s) and the first end time (t 1e) and / or the second end time (t 2e) is equal to the first end time (t 1e).In some applications, it may be expedient for the first ultrasonic torque angular frequency (f 1m) at the first end time (f 1e) to be equal to the second ultrasonic torque angular frequency (f 2m) at the second end time (f 2e).In other application cases, it may be expedient if the first ultrasonic torque angular frequency (f 1m) at the first starting time (f 1s) is equal to the second ultrasonic torque angular frequency (f 2m) at the second starting time (f 2s).In yet other application cases, it may be useful if the first ultrasonic torque angular frequency (f 1m) at the first starting time (f 1s) is different from the second ultrasonic torque angular frequency (f 2m) at the second starting time (f 2s).And in yet other application cases, it may be useful if the first ultrasonic torque angular frequency (f 1m) at the first end time (f 1e) is different from the second ultrasonic torque angular frequency (f 2m) at the second end time (f 2e).A method for emitting an ultrasonic signal, further developed from the above methods, comprises the steps a. of generating the first ultrasonic subburst with a first ultrasonic transducer (UBS1) and / or b. of generating the second ultrasonic subburst with a second ultrasonic transducer (UBS2) that is different from the first ultrasonic transducer (UBS1).Preferably, the first ultrasound transducer (US1) has a first resonant frequency (f 1) and the second ultrasound transducer (US2) has a second resonant frequency (f 2) wherein the first resonant frequency (f 1) of the first ultrasound transducer (US1) is different from the second resonant frequency (f 2) of the second ultrasound transducer (US2). This allows additional information to be used for object classification of the objects (O).In this case, the first ultrasonic transducer (US 1) preferably has a first bandwidth (Δf 1) with a first upper half maximum amplitude frequency (f 1o) and a first lower half maximum amplitude frequency (f 1u). The second ultrasonic transducer (US1) preferably has a second bandwidth (Δf 2) with a second upper half maximum amplitude frequency (f 2o) and a second lower half maximum amplitude frequency (f 2m). The first bandwidth (Δf 1) and the second bandwidth (Δf 2) overlap in the frequency domain. This has the advantage that a frequency sweep can be carried out over a larger frequency range. It is thus preferably the case, a. the difference of the amount of the first upper half-maximum amplitude frequency (f 1o) minus the amount of the second lower half-maximum amplitude frequency (f 2m) is preferably greater than the difference of the amount of the first upper half-maximum amplitude frequency (f 1o) minus the amount of the first lower half-maximum amplitude frequency (f 1u) and / or b. the difference of the amount of the first upper half-maximum amplitude frequency (f 1o) minus the amount of the second lower half-maximum amplitude frequency (f 2m) is preferably greater than the difference of the amount of the second upper half-maximum amplitude frequency (f 2o) minus the amount of the second upper half-maximum amplitude frequency (f The difference between the magnitude of the second upper half maximum amplitude frequency (f 2o) minus the magnitude of the first lower half maximum amplitude frequency (f 1u) is preferably greater than the difference between the magnitude of the first upper half maximum amplitude frequency (f 1o) minus the magnitude of the first lower half maximum amplitude frequency (f 1u) and / or d. the difference between the magnitude of the second upper half maximum amplitude frequency (f 2o) minus the magnitude of the first lower half maximum amplitude frequency (f 1u) is preferably greater than the difference between the magnitude of the first upper half maximum amplitude frequency (f 1o) minus the magnitude of the first lower half maximum amplitude frequency (f 1u).Furthermore, it is advantageous if the angle-dependent first energy density of the first sound radiation of the first ultrasound transducer (US 1) is different from the angle-dependent second energy density of the second sound radiation of the second ultrasound transducer (US 2) and / or the angle-dependent first sound amplitude of the first sound radiation of the first ultrasound transducer (US 1) is different from the angle-dependent second sound amplitude of the second sound radiation of the second ultrasound transducer (US 2). As explained in the figures, this makes it possible to obtain information about the angular range and about the distance of an object (O 1, O 2) from the reflection signal.In addition to the methods described so far for transmitting ultrasonic bursts, there are also analogous methods for receiving the ultrasonic bursts.The ultrasonic signal which is now received and which has typically been previously reflected on an object has previously preferably been generated with the aid of one of the methods described above. The complex structure of the ultrasonic signals is discussed in more detail in the descriptions of the figures. Therefore, the figures with the frequency characteristics are recommended here to be overlaid in a short course to understand which type of ultrasonic bursts are to be received. A first ultrasound transducer (US1) and a second ultrasound transducer (US2) are intended to be part of a common ultrasound sensor system (USS) for this purpose. The ultrasonic sensor system (USS) is intended to have an ultrasonic system axis (USA). The method for receiving the complex ultrasonic bursts comprises the steps of a. receiving the reflected ultrasonic signal with a first ultrasonic transducer (US1) as a first ultrasonic receiving signal, the first ultrasonic transducer having a first resonant frequency (f1), and b. receiving the reflected ultrasonic signal with a second ultrasonic transducer (US2) as a second ultrasonic receiving signal, the second ultrasonic transducer (US2) having a second resonant frequency (f2), and c. processing the first ultrasonic receiving signal and the second ultrasonic receiving signal and d. concluding distances from objects (O1, O2) which have reflected the ultrasonic signal, to the common ultrasound system (USS) and e. of concluding on an angle between the line of sight from the common ultrasound system (USS) to objects (O1, O2) which have reflected the ultrasound signal, on the one hand, and the ultrasound system axis (USA) of the common ultrasound system (USS), on the other hand, or concluding on an angle range in which the objects (O1, O2) are respectively located.What has been described so far results in a method for determining an object position, the execution of a method with the aid of the different sound cones of the different ultrasound transducers (US1-US2, US3) with the aid of a first common ultrasound system (USS1) for determining a first distance (s1) and a first angle or first angle range, and the analogous execution of this method with the aid of a preferably, but not necessarily identically constructed, second common ultrasound system (USS2) which is different from the first common ultrasound system (USS1) - i.e. not identical thereto - and spaced apart, for determining a second distance (s2) and a second angle or a second distance and second angle range. According to this method, a spatial coordinate or a spatial area in which an object (O) that has reflected the ultrasonic signal is located is then ascertained on the basis of the first distance (s 1) and the second distance (s 2), and of the ascertained first angular range and the ascertained second angular range. The information corresponding to the first angular range and the first distance (s 1) corresponds to a first spatial range approximately in the shape of a first torus at the first distance from the first ultrasonic sensor system (USS 1). The information corresponding to the second angular range and the second distance (s 1) corresponds to a second spatial range approximately in the form of a second torus at the second distance from the second ultrasonic sensor system (USS 2). The intersection of the spatial points which are located both within the first spatial area and the second spatial area results in a reduced further spatial area in which the object in question should be located.Further disclosed herein is another method of emitting an ultrasonic burst for use in vehicle ultrasonic sensor systems comprising the steps of:Step 1: transmitting an ultrasonic burst having an ultrasonic burst duration (bd) not exceeding a maximum ultrasonic burst duration (bd) by an ultrasonic sensor system (USS);- Step 2: receiving an ultrasonic burst reflected by an object (O);Step 3: Determining the distance (D) between the ultrasonic sensor system (USS) and the object (O) as a function of the received reflected ultrasonic burst;Step 4: Repeating steps 1 to 4, wherein the ultrasonic burst duration (bd) depends on the determined distance (D, s1, s2).It has been found that it is advantageous if the ultrasonic burst length of the ultrasonic burst duration (bd) is extended in time, i.e. increased in terms of amount, with the fourth root of the distance (D) determined in accordance with the formula. This has the advantage that the total energy which returns to the emitting ultrasonic transducer during a reflection allows conclusions to be drawn about the object, since this amount of energy no longer depends on the distance, but only on the size and reflectivity of the object. It is sufficient if such ultrasonic pulses corrected in the burst length (bd) are transmitted from time to time. If, for example, a plurality of objects have been localized at different distances, it may be expedient to emit an ultrasonic burst (UB) optimized for the distance of this object for each object detected.A method for transmitting an ultrasonic burst for use in ultrasonic sensor systems in vehicles is then obtained, having the following steps:Step 1: transmitting an ultrasonic burst having an ultrasonic burst property by an ultrasonic sensor system (USS);- Step 2: receiving an ultrasonic burst reflected by an object (O);Step 3: Determining and evaluating a property of the object (O) depending on the received reflected ultrasonic burst and / or optionally a plurality of received reflected ultrasonic bursts;Step 4: Repeating Steps 1 to 4, wherein at least one ultrasonic burst property of a subsequently transmitted ultrasonic burst depends on the evaluation of the property determined.It is essential that one of the subsequently transmitted ultrasonic bursts does not have to immediately follow the preceding ultrasonic burst. Rather, it is conceivable to send further ultrasonic bursts between these two ultrasonic bursts, which have different measurement tasks. Such sequences of ultrasonic bursts may be mixed. Thus, the ultrasonic burst property of an ultrasonic burst to be transmitted may depend on one or more objects in the environment of the ultrasonic sensor system (USS) or the environment of the ultrasonic sensor system (USS). The ultrasonic burst property of an ultrasonic burst to be transmitted can thus depend on one or more objects in the environment of a vehicle or on the environment of the vehicle if such an ultrasonic sensor system (USS) is installed in the vehicle. A plurality of ultrasonic burst properties are described below, which can also relate to the properties of a plurality of ultrasonic bursts.There may then be obtained, for example, a method for emitting an ultrasonic burst for use in ultrasonic sensor systems in vehicles, which method comprises the following steps:Step 1: transmitting a first ultrasonic burst having an ultrasonic burst characteristic with a first ultrasonic burst characteristic value by an ultrasonic sensor system (USS);- Step 2: receiving a first ultrasonic burst reflected by a first object (O);Step 3: Determining and evaluating a first property of the first object (O1) as a function of the received reflected first ultrasonic burst and / or optionally a plurality of received reflected first ultrasonic bursts;Step 4: transmitting a second ultrasonic burst having the ultrasonic burst property with a second ultrasonic burst property value by the ultrasonic sensor system (USS);- Step 5: receiving a second ultrasonic burst reflected by a second object (O);step 6: determining and evaluating a second property of the second object (O2) as a function of the received reflected second ultrasonic burst and / or optionally a plurality of received reflected second ultrasonic bursts;Step 7: Repeating Steps 1 to 6,▪ wherein at least the first ultrasonic burst property of a subsequently transmitted first ultrasonic burst depends on the evaluation of the determined first property, and▪ wherein at least the second ultrasonic burst property of a subsequently transmitted second ultrasonic burst depends on the evaluation of the determined second property.It is important here that further ultrasonic bursts can also be inserted here for other purposes. Also, first ultrasonic bursts may be transmitted more or less frequently compared to the second ultrasonic bursts.Thus, how the ultrasonic burst duration (bd) can be optimized object-dependently, the ultrasonic burst amplitude can also be optimized object-dependently. It may thus be useful if the amplitude (A) of at least three ultrasonic bursts transmitted in direct or non-direct chronological sequence depends substantially proportionally to (D+D 0)1 / k, where 2≤k≤5or preferably k=2 or k=4, on the distance (D) determined, wherein D 0 is a constant which may be zero. In this case, further ultrasonic bursts (UB) for measuring other objects and environmental properties can be transmitted between these ultrasonic bursts (UB).Typically, a plurality of ultrasonic bursts (UB) are transmitted at an ultrasonic burst interval, wherein the first ultrasonic burst interval is the interval between the ultrasonic burst start (UBS) of a first ultrasonic burst and the ultrasonic burst start (UBS) of the second ultrasonic burst immediately following this first ultrasonic burst, and wherein the second ultrasonic burst interval between the ultrasonic burst start (UBS) of the second ultrasonic burst and the ultrasonic burst start (UBS) of the third ultrasonic burst immediately following this second ultrasonic burst depends on the determined interval (D) of an object (O, O, O2).A further possible variation of an ultrasonic burst property is a variation of the temporal ultrasonic burst distance of the ultrasonic bursts. The temporal ultrasonic burst distance of the ultrasonic bursts can become shorter in time, for example, as the spatial distance (D) between the ultrasonic sensor system and the object (O) decreases. In this case, the temporal ultrasonic burst distance of the ultrasonic bursts is preferably shorter by a length I when the spatial distance (D) between the ultrasonic sensor system and object (O) is shortened by a time 2*I / c with c as the speed of sound with a tolerance of + / - 25% and / or better with a tolerance of + / - 10% and / or better with a tolerance of + / - 5%.As a further possible variation of an ultrasonic burst property, the number of ultrasonic burst moment frequencies (f m1, f m2, f m3) and the associated number of frequency profiles (SF1, SF2, SF3) of these ultrasonic burst moment frequencies (f m1, f m2, f m3) within an ultrasonic burst (UB) can depend on the distance (D).A further modification of an ultrasonic burst property may be that an ultrasonic burst has at least two of the following time segment types:• a single-mode time (smt 1, smt 2, smt 3, smt1, smt2) and / or• a dual-mode time (dmt 12, dmt 23, dmt1, dmt2) and / or• a tri-mode time (t mt, tmt 123, tmt 112).This ultrasonic burst property can also depend on objects in the environment or the environment in parts or as a whole. Such ultrasonic sensor systems are preferably used in vehicles. This is then preferably an ultrasonic sensor system (USS) for a vehicle, with a first ultrasonic transducer (US 1), with a second ultrasonic transducer (US 2). Of course, the ultrasonic sensor system can also have more than two ultrasonic transducers (US1, US2, US3). In our example, the first ultrasound transducer (US1) has a first resonant frequency (f 1) and the second ultrasound transducer (US2) has a second resonant frequency (f 2), wherein the first resonant frequency (f 1) is different from the second resonant frequency (f 2).Preferably, the first ultrasonic transducer (US1) has a first bandwidth (Δf 1) and the second ultrasonic transducer (US2) has a second bandwidth (Δf 2). In order to allow chirping to be performed over the full bandwidth without significant amplitude dips, it is expedient if the first bandwidth (Δf 1) of the first ultrasound transducer (US 1) and the second bandwidth (Δf 2) of the second ultrasound transducer (US 2) overlap.The ultrasonic sensor system (USS) is preferably designed such that the ultrasonic sensor system (USS) can emit an ultrasonic burst (UB) with an ultrasonic burst instantaneous frequency (f m) which is dependent on the time (t) and cannot be emitted at at least one point in time during the emission of the ultrasonic burst (UB) by an ultrasonic transducer of the ultrasonic transducers (US1, US2) of the ultrasonic sensor system (USS). This thus describes a bandwidth increase compared to a single ultrasonic transducer with regard to transmission.Analogously, the ultrasonic sensor system (USS) is preferably designed such that the ultrasonic sensor system (USS) can receive an ultrasonic burst (UB) with an ultrasonic burst torque frequency (f m) which is dependent on the time (t) and cannot be received at at least one point in time during the emission of the ultrasonic burst (UB) by an ultrasonic transducer of the ultrasonic transducers (US1, US2) of the ultrasonic sensor system (USS). This thus describes a bandwidth increase compared to a single ultrasonic transducer with respect to reception.Preferably, the ultrasonic sensor system (USS) can emit an ultrasonic burst (UB) which has more than one ultrasonic burst torque frequency (f m1, f m2, f m3) in its spectrum, wherein each of the ultrasonic burst torque frequencies (f m1, f m2, f m3) during such an ultrasonic burst lies substantially in the bandwidth (Δf 1, Δf 2, Δf 3) of at least one of the ultrasonic transducers (US1, US2, US3). This too is an ultrasonic burst property which can depend on the examination target, typically an object (O, O1, O2) in the environment of the ultrasonic sensor system or the vehicle. Conversely, the ultrasonic sensor system (USS) may then typically receive an ultrasonic burst (UB) having more than one ultrasonic burst instantaneous frequency (f m1, f m2, f m3) in its spectrum, each of the ultrasonic burst instantaneous frequencies (f m1, f m2, f m3) during such an ultrasonic burst being substantially in the bandwidth (Δf 1, Af 2, Δf 3) of at least one of the ultrasonic transducers (US1, US2, US3). Preferably, the output signals of the ultrasonic transducers are then combined to form an ultrasonic reception signal. In the simplest case, this can be done, for example, by summing the output signals of the ultrasonic transducers.An ultrasonic sensor system (USS) is also conceivable in which the ultrasonic sensor system (USS) can receive an ultrasonic burst (UB) which has more than one ultrasonic burst instantaneous frequency (f m1, f m2, f m3) in its spectrum at least one point in time during the burst duration (bd), wherein each of the ultrasonic burst instantaneous frequencies (f m1, f m2, f m3) during such an ultrasonic burst substantially in the bandwidth (Δf 1, Δf 2, Δf 3) of at least one of the ultrasonic transducers (US1, US2, us3) and wherein at least one of these ultrasonic burst instantaneous frequencies (f m1, f m2, f m3) is then not in the bandwidth (Δf 1, Δf 2, Δf 3) of at least one of the ultrasonic transducers (US1, US2, US3) at least at one time during such an ultrasonic burst. Thus, the use of multiple ultrasonic transducers results in an increase in the bandwidth with respect to reception.In one possible configuration, a plurality of ultrasonic transducers (US 1, US 2) of an ultrasonic sensor system (USS) are driven by means of a common drive signal (AS). This has the advantage that such an ultrasonic sensor system (USS) behaves essentially like a single ultrasonic transducer for driving circuits, if appropriate.Similarly, a common ultrasonic reception signal can be generated from the output signals of the ultrasonic transducers (US 1, US 2), which signal can also comprise a plurality of partial signals.Such an ultrasonic sensor system (USS) can be designed such that the sound radiation lobe of the first ultrasonic transducer (US1) has a first vertical aperture angle (α v) and the sound radiation lobe of the second ultrasonic transducer (US2) has a second vertical aperture angle (β v) and that the reception lobe of the first ultrasonic transducer (US1) has a first vertical aperture angle (α V) and the reception lobe of the second ultrasonic transducer (US2) has a second vertical aperture angle (β V) respectively. In this case, the first vertical opening angle (α V) should then be different from the second vertical opening angle (β V) so that a reflected ultrasonic signal has different frequencies which code in which angle range about the axis (USA) of the ultrasonic sensor system (USS) the reflecting object is possibly located.In an analogous manner, the sound radiation lobe of the first ultrasonic transducer (US1) has a first horizontal aperture angle (α H) and the sound radiation lobe of the second ultrasonic transducer (US2) has a second vertical aperture angle (β V) and the reception lobe of the first ultrasonic transducer (US1) has a first horizontal aperture angle (α H) and the reception lobe of the second ultrasonic transducer (US2) has a second vertical aperture angle (β V) respectively. Here too, the first horizontal opening angle (α H) is preferably different from the second vertical opening angle (β V) which results in an analogous advantage.The proposed ultrasonic sensor system very particularly preferably has further ultrasonic transducers in addition to the first ultrasonic transducer (US 1) and the second ultrasonic transducer (US 2), so that an ultrasonic transducer array results in which the ultrasonic transducers (US 1, US 2, US 3) have different resonant frequencies (f 1, f 2, f 3). In the simplest case, the proposed ultrasonic sensor system also has a third ultrasonic transducer (US 3) in addition to the first ultrasonic transducer (US 1) and the second ultrasonic transducer (US 2), wherein the third ultrasonic transducer (US 3) has a third resonant frequency (f 3) which is preferably different from the second resonant frequency (f 2) and from the first resonant frequency (f 1).In this case with three ultrasonic transducers (US1, US2, US3), the ultrasonic transducers (US1, US2, US3) are preferably arranged in an isosceles triangle. The edge lengths of this isosceles triangle are preferably less than ten times the diameter of the sound emission surfaces of the ultrasound transducers (US1, US2, US3) and / or better less than five times the diameter of the sound emission surfaces of the ultrasound transducers (US1, US2, US3) and / or better less than three times the diameter of the sound emission surfaces of the ultrasound transducers (US1, US2, US3) and / or better less than twice the diameter of the sound emission surfaces of the ultrasound transducers (US1, US2, US3).In an analogous manner, a method for receiving an ultrasonic signal results, wherein the ultrasonic signal comprises an overall ultrasonic burst (UB) comprising a first ultrasonic subburst and a second ultrasonic subburst. Each ultrasonic subburst of the ultrasonic subbursts also comprises here at least two ultrasonic pulses (P 0 to P 7), of which each of the at least two ultrasonic pulses (P 0 to P 7) of an ultrasonic subburst has a temporal ultrasonic pulse start and a temporal ultrasonic pulse end. As before, the ultrasonic period (T 1 to T 7) of an individual ultrasonic pulse (P 0 to P 7) of an ultrasonic subburst, hereinafter referred to as the respective ultrasonic pulse, is the time from the temporal ultrasonic pulse end of the ultrasonic pulse immediately preceding the respective ultrasonic pulse to the temporal ultrasonic pulse end of the respective ultrasonic pulse. The first ultrasonic instantaneous frequency (f 1m) of the first ultrasonic subburst is again the reciprocal of the instantaneous ultrasonic period (T 1m) of the first ultrasonic subburst and the second ultrasonic instantaneous frequency (f 2m) of the second ultrasonic subburst is again the reciprocal of the instantaneous ultrasonic period (T 2m) of the second ultrasonic subburst. The first ultrasound subburst begins at a first start time (t 1s), which is equal to the ultrasound pulse start of the first ultrasound pulse (P 0) of the first ultrasound subburst. The first ultrasound subburst ends at a first end time (t 1e), which is equal to the ultrasound pulse end of the last ultrasound pulse (P7) of the first ultrasound subburst. The first ultrasound subburst has a first ultrasound subburst duration (t 1e- t 1s), which corresponds to the value of the time difference between the first end time (t 1e) minus the first start time (t 1s). The second ultrasound subburst begins at a second start time (t 2s), which is equal to the ultrasound pulse start of the first ultrasound pulse (P 0) of the second ultrasound subburst. The second ultrasound subburst ends at a second end time (t 2e), which is equal to the ultrasound pulse end of the last ultrasound pulse (P7) of the second ultrasound subburst. The second ultrasound subburst has a second ultrasound subburst duration (bd=t 2e- t 2s), which corresponds to the value of the time difference between the second end time (t 2e) minus the second start time (t 2s). The first ultrasonic torque frequency (f 1m) is preferably different from the second ultrasonic torque frequency (f 2m) at at least one time between the first starting time (t 1s) and the first ending time (t 1e) and simultaneously between the second starting time (t 2s) and the second ending time (t 2e). The receiving method then comprises the steps of:• Receiving the overall ultrasound burst (UB) by means of an ultrasound sensor system (USS) with at least a first ultrasound transducer (US1) and a second ultrasound transducer (US2), wherein the first ultrasound transducer (US1) has a first resonant frequency (f 1) and a first bandwidth (Δf 1) and wherein the second ultrasound transducer (US2) has a second resonant frequency (f 2) and a second bandwidth (Δf 2) and wherein the first resonant frequency (f 1) is different from the second resonant frequency (f 2) and wherein the first bandwidth (Δf 1) overlaps the second bandwidth (Δf 2) and wherein the first ultrasound transducer (US1) generates a first ultrasound reception sub-signal and wherein the second ultrasound transducer (US2) generates a second sub-signal of ultrasonic reception;• generating an ultrasonic reception signal from the first ultrasonic reception sub-signal and the second ultrasonic reception sub-signal, wherein the ultrasonic reception signal may comprise a plurality of sub-reception signals and wherein one or more sub-reception signals may coincide with ultrasonic reception sub-signals;• Determination of environmental information on the basis of the ultrasonic reception signal.Typically, at least at one time during the burst duration (bd) of the overall ultrasonic burst, the first ultrasonic instantaneous frequency (f 1m) is not within the first bandwidth (Δf 1) of the first ultrasonic transducer (US1), but within the second bandwidth (Δf 2) of the second ultrasonic transducer (US2), and / or the first ultrasonic instantaneous frequency (f 1m) is not within the second bandwidth (Δf 2) of the second ultrasonic transducer (US2), but within the first bandwidth (Δf 1) of the first ultrasonic transducer (US1), the second ultrasonic instantaneous frequency (f 2m) not within the first bandwidth (Δf 1) of the first ultrasonic transducer (US1) but within the second bandwidth (Δf 2) of the second ultrasonic transducer (US2), and / or the second ultrasonic instantaneous frequency (f 2m) not within the second bandwidth (Δf 2) of the second ultrasonic transducer (US2) but within the first bandwidth (Δf 1) of the first ultrasonic transducer (US1).A refinement of the method can comprise the step of concluding a distance to an object (O1, O2) and an angle range in which this object (O1, O2) is located on the basis of differences between the first ultrasonic reception sub-signal and the second ultrasonic reception sub-signal or on the basis of differences in signals derived therefrom. In particular, neural networks or other pattern recognition methods can be used for this purpose.The method for receiving an overall ultrasonic burst may be characterized in that a received overall ultrasonic burst comprises at least two of the following time-section types:• a single-mode time (smt 1, smt 2, smt 3, smt1, smt2) and / or• a dual-mode time (dmt 12, dmt 23, dmt1, dmt2) and / or• a tri-mode time (t mt, tmt 123, tmt 112)Under this condition, the method can then comprise the following steps, among other things:• receiving the total ultrasonic burst and generating said ultrasonic receive signal, which may comprise a plurality of sub-receive signals;• detecting the first type of time interval at a first time within the burst duration (bd) of the overall ultrasound burst;• Ascertaining environmental information on the basis of the ultrasonic reception signal as a function of the ascertained first time interval type.This method can be refined by comprising the following steps:• detecting the second type of time interval at a second time within the burst duration (bd) of the overall ultrasonic burst different from the first time;• Determination of environmental information on the basis of the ultrasonic reception signal as a function of the determined first time interval type within a first time interval within the burst duration (bd) of the overall ultrasonic burst;• Ascertainment of environmental information on the basis of the ultrasonic reception signal as a function of the ascertained second time interval type within a second time interval within the burst duration (bd) of the overall ultrasonic burst,The first time segment and the second time segment should preferably not overlap. At least, however, they should not overlap completely.Ultrasonic transducers have always been written in this document. It is obvious to the person skilled in the art that with regard to the transmission of the total ultrasonic bursts, ultrasonic transmitters can also be used which are used and / or suitable only for transmitting the total ultrasonic bursts. It is also obvious to the person skilled in the art that with regard to the reception of the total ultrasonic bursts, ultrasonic receivers can also be used which are used and / or suitable only for the reception of the total ultrasonic bursts. In this respect, the claims also encompass combinations of ultrasound transducers with one or more pure ultrasound receivers with respect to reception with the term ultrasound transducer, and also combinations of ultrasound transducers with one or more pure ultrasound transmitters with respect to the transmission of overall ultrasound bursts with the term ultrasound transducer.In extreme cases, they can be only pure ultrasonic receivers or only pure ultrasonic transmitters.For example, it is conceivable to combine one or a few ultrasound transducers used for transmission and reception with a larger number of pure ultrasound receivers. The pure ultrasound receivers can be produced inexpensively on a MEMS basis, while the ultrasound transmitters can be constructed in the form of the ultrasound transducers in the form of piezo-based vibrating ceramics.On this basis, an ultrasonic sensor system (USS), in particular for a vehicle or a robot or another moving machine, can then be defined, which has a first, typically smaller number of ultrasonic emitters and / or ultrasonic transducers, each having a piezoceramic as sound-generating emitter element, and which comprises a second number of pure ultrasonic receivers. Preferably, at least one of these one ultrasonic receivers is a MEMS-based ultrasonic receiver. The number of pure MEMS ultrasonic receivers is very particularly preferably high. Preferably, at least some of the ultrasound transmitters and / or ultrasound transducers and / or ultrasound receivers form an ultrasound system as described above.Advantage Of the InventionSuch an ultrasonic sensor system (USS) enables, at least in some implementations, the transmission and / or reception of more complex ultrasonic bursts than are possible with individual ultrasonic transducers and / or ultrasonic transmitters and / or ultrasonic transmitters. This is important in particular in the course of creating environment maps and point clouds of the environment for autonomous driving. However, the advantages are not limited to this.List of the FiguresFIG. 1a as part of FIG. 1 shows the profile of the ultrasonic burst amplitude (A) as a function of the burst duration (bd). FIG. 1 b, as part of FIG. 1, shows a proposed burst duration as a function of the object distance (D) from the next object. FIG. 1c, as part of FIG. 1, shows the ultrasonic burst amplitude (A) as a function of the object distance (D). FIG. 2 ashows schematically in a simplified manner the temporal signal profile of a single extracted exemplary ultrasonic burst (UB). FIG. 2 bshows the associated temporal profile of the ultrasonic burst torque frequency (f m) plotted against the time (t) over the burst duration (bd). FIGS. 2 c 2 c show an exemplary variation of the frequency change speed (v f) of the ultrasonic burst torque frequency (f m) over time (t) of the burst duration (bd). FIG. 3 shows an exemplary first spectral ultrasonic burst amplitude (A1) of a first ultrasonic transducer (US1) for the amplitude (A) of the sound radiation of one of these ultrasonic transducers (US1) when excited with a first excitation signal having the first excitation frequency (f A1). FIG. 4 shows an exemplary second spectral ultrasonic burst amplitude (A2) for the amplitude (A) of the sound radiation of a second ultrasonic transducer (US2) when excited with a second excitation signal (AS2) with the second excitation frequency (f A2). FIG. 5A shows an exemplary third spectral ultrasonic burst amplitude (A3) for the amplitude (A) of the sound radiation of a third ultrasonic transducer (US3) when excited with a transmission signal of the third excitation frequency (fA3). FIG. 6 shows, by way of example, in two extreme configurations, the superposition of a first, second and third amplitude spectrum. FIGS. 7 to 10 show basically possible types of a frequency sweep. FIG. 11 shows an exemplary arrangement consisting of a first ultrasound transducer (US 1) and a second ultrasound transducer (US 2) and a third ultrasound transducer (US 3). FIG. 12 corresponds to FIG. 7 with the difference that a frequency sweep is now generated with the aid of three ultrasonic sensors (US 1, US 2, US 3). FIG. 13 is a simplified and schematic illustration of an exemplary system for generating the exemplary frequency response of FIG. 12. FIG. 14 corresponds in essential parts to FIG. 12, wherein now, however, the excitation signal (AS) temporarily comprises more than one excitation frequency (fA). FIG. 15 shows in simplified form and schematically an exemplary system for generating the exemplary frequency profile of the following FIG. 16. FIG. 16 corresponds to FIG. 12 with the difference that a first frequency profile (SF1), a second frequency profile (SF2) and a third frequency profile (SF3) are now used together to generate an ultrasonic burst (UB). FIG. 17 corresponds to FIG. 16 with the difference that now all frequency characteristics (SF1, SF2, SF3) at a common end frequency (f e) end as respective ultrasonic moment angular frequency (f m1, f m2, f m3) at a common end time (t e). FIGS. 18 and 19 show the sound radiation of an ultrasonic sensor system (USS) with different resonant frequencies and opening angles. FIG. 20 illustrates how the different modulation types described above can now be used when approaching an important object (O), for example an obstacle. FIG. 21 illustrates the situation when using two ultrasonic sensor systems (USS1, USS2) FIG. 22 shows the profile of the ultrasonic moment frequencies and their effect on the Doppler stability.DESCRIPTION OF THE FIGURESFIG. 1 shows a schematic view of FIG. 1FIG. 1 shows in FIG. 1 athe profile of the ultrasonic burst amplitude (A) as a function of the burst duration (bd) (see also FIG. 2 ). As the ultrasound burst becomes longer, i.e. a Bust duration (bd) becomes longer, the ultrasound burst amplitude (A) decreases.FIG. 1 bshows a proposed burst duration as a function of the object distance (D) to the next object. The burst duration is not only increased with increasing object distance (D). Preferably, the ultrasonic burst length of the ultrasonic burst duration (BD) increases with the square root or the fourth root of the object distance (D). This firstly extends the latency time. The signal reflected by the object is raised, however, in such a way that the reduction of the reception amplitude, which is at 1 / D 4 is improved to a reduction of 1 / D 2. Even more preferably, the ultrasonic burst length of the ultrasonic burst duration (bd) is increased with the fourth root of the distance according to the formula bd=bd 1* D -1 / 4+ bd 0 with bd 0 and bd 1 as constants. As a result, the total signal amplitude remains constant after reception and correlation in a correlator for the object to be measured.In order to avoid overdrive in the near range, the burst duration (bd) in the vicinity of the object is not only decreased. Preferably, the ultrasonic burst amplitude is also lowered in the vicinity of the object. As a result, the reception amplitude after the reception and correlation have taken place can still be kept constant even if a shortening of the burst duration (bd) is no longer meaningful. It is thus proposed here to readjust the burst duration of the ultrasonic bursts and the ultrasonic burst amplitude (A) in such a way that the reception amplitude of the observed object remains constant or follows a predefined sensitivity curve. FIG. 1 cshows the ultrasonic burst amplitude (A) as a function of the object distance (D).FIG. 2 shows a schematic view of FIG. 2FIG. 2 ashows schematically in a simplified manner the temporal signal profile of a single extracted exemplary ultrasonic burst (UB). The ultrasonic burst (UB) begins at the time of the ultrasonic burst start (UBS). The ultrasonic burst (UB) ends at the time of the end of the ultrasonic burst (UBE). The time between Ultrasonic Burst Start (UBS) and Ultrasonic Burst End (UBE) is the burst duration (BD). The ultrasonic burst (UB) has an ultrasonic burst amplitude (A), which can be understood here as the average amplitude of the ultrasonic burst (UB) over the burst duration (BD) of the relevant ultrasonic burst (UB).In the example of FIG. 2 a, the ultrasonic burst (UB) illustrated there has eight ultrasonic periods each with one ultrasonic pulse, i.e., here, for example, eight ultrasonic pulses (P 0 to P 7). The zeroth ultrasonic pulse (P 0) is associated with the zeroth ultrasonic period existing only half. The ultrasonic periods (P 0 to P 7) of the ultrasonic burst (UB) have eight ultrasonic period durations (T 0 to T 7) respectively. The zeroth ultrasonic period duration (T 0) is defined here, in the sense of this document, as twice the temporal pulse width of the zeroth ultrasonic pulse (P 0). The ultrasonic moment incident frequency (f jm) of the j-th ultrasonic pulse (P j) of the j-th ultrasonic period is understood in this document to mean the reciprocal of the j-th ultrasonic period duration (T j) of the j-th ultrasonic period.FIG. 2 b shows the associated temporal profile of the ultrasonic burst torque frequency (f m) versus time (t) plotted in sketch form and by way of example over the burst duration (bd). In the example of FIG. 2 b, the ultrasonic burst torque frequency (f m) increases abruptly as a result of the start of the ultrasonic burst (UB) at the time of the ultrasonic burst start (UBS). In the example of FIG. 2 a, the ultrasonic burst torque frequency (f m) is then preferably continuously lowered at least temporarily following a hyperbolic period as far as the ultrasonic burst end (UBE).FIG. 2 cshows an exemplary curve of the frequency change speed (v f) of the ultrasonic burst torque frequency (f m) over time (t) of the burst duration (bd). Initially, the frequency increases with a large positive frequency rate of change (v f) due to the ultrasonic burst start (UBS) of 0 Hz. The frequency change speed (v f) is then briefly strongly negative in this example and then increases linearly in this example. The magnitude of the frequency change speed (v f) decreases linearly in this example.FIG. 3 shows a schematic view of FIG. 3FIG. 3 is used herein to explain basic terminology for understanding terms used herein. FIG. 3 shows an exemplary first spectral ultrasonic burst amplitude (A1) of a first ultrasonic transducer (US1) for the amplitude (A) of the sound radiation of one of these ultrasonic transducers (US1) when excited with a first excitation signal having the first excitation frequency (f A1). The exemplary first spectral ultrasonic burst amplitude (A1) has a first amplitude maximum (A max1) of the sound radiation of the first ultrasonic transducer (US1) at a first resonant frequency (f 1) of the first ultrasonic transducer (US1). In the example of FIG. 3, the exemplary first ultrasonic transducer (US 1) has a first bandwidth (Δf 1) of the first spectral ultrasonic burst amplitude (A 1) for the amplitude (A) of the sound radiation of a first ultrasonic transducer (US 1). In this document, this first bandwidth (Δf 1) of a first spectral ultrasonic burst amplitude (A1) is defined here for the amplitude (A) of the first sound radiation of a first ultrasonic transducer (US1) such that this first bandwidth (Δf 1) of the first ultrasonic sensor (US1) is the first upper half maximum amplitude frequency (f 1o), at which the amplitude (A) of the sound radiation of the first ultrasonic transducer (US1) is half the first amplitude maximum (A max1) of the sound radiation of the first ultrasonic transducer (US1) at its first resonant frequency (f 1), minus the first lower half maximum amplitude frequency (f 1u), at which the amplitude (A) of the sound radiation of the first ultrasound transducer (US1) is likewise half the first amplitude maximum (A max1) of the sound radiation of the first ultrasound transducer (US1) at its first resonant frequency (f 1).FIG. 4 shows a schematic of FIG. 4FIG. 4 is used herein to explain basic terminology for understanding terms used herein. FIG. 4 shows an exemplary second spectral ultrasonic burst amplitude (A2) for the amplitude (A) of the sound radiation of a second ultrasonic transducer (US2) when excited with a second excitation signal (AS2) with the second excitation frequency (f A2). The exemplary second spectral ultrasonic burst amplitude (A2) has a second amplitude maximum (A max2) of the sound radiation of the second ultrasonic transducer (US2) at a second resonant frequency (f 2) of the second ultrasonic transducer (US2). In the example of FIG. 4, the exemplary second ultrasonic transducer (US 2) has a second bandwidth (Δf 2) of the second spectral ultrasonic burst amplitude (A 2) for the amplitude (A) of the sound radiation of a second ultrasonic transducer (US 2). In this document, this second bandwidth (Δf 2) of a second amplitude spectrum (A2) for the amplitude (A) of the second sound radiation of a second ultrasonic transducer (US2) is defined here such that this second bandwidth (Δf 2) of the second ultrasonic sensor (US2) is the second upper half maximum amplitude frequency (f 2o), at which the amplitude (A) of the sound radiation of the second ultrasonic transducer (US2) is half the second amplitude maximum (A max2) of the sound radiation of the second ultrasonic transducer (US2) at its second resonant frequency (f 2), minus the second lower half maximum amplitude frequency (f 2u), at which the amplitude (A) of the sound radiation of the second ultrasound transducer (US2) is likewise half the second amplitude maximum (A max2) of the sound radiation of the second ultrasound transducer (US2) at its second resonant frequency (f 2).FIG. 5 shows a schematic view of FIG. 5FIG. 5 is also used herein to explain basic terminology for understanding terms used herein. FIG. 5 shows an exemplary third spectral ultrasonic burst amplitude (A3) for the amplitude (A) of the sound radiation of a third ultrasonic transducer (US3) when excited with a transmission signal of the third excitation frequency (f A3). The exemplary third spectral ultrasonic burst amplitude (A3) has a third amplitude maximum (A max3) of the sound radiation of the third ultrasonic transducer (US3) at a third resonant frequency (f 3) of the third ultrasonic transducer (US3). In the example of FIG. 5, the example third ultrasonic transducer (US 3) has a third bandwidth (Δf 3) of the third spectral ultrasonic burst amplitude (A3) for the amplitude (A) of the sound radiation of a third ultrasonic transducer (US 3). In this document, this third bandwidth (Δf 3) of a third spectral ultrasonic burst amplitude (A3) is defined here for the amplitude (A) of the third sound radiation of a third ultrasonic transducer (US3) such that this third bandwidth (Δf 3) of the third ultrasonic sensor (US3) is the third upper half maximum amplitude frequency (f 3o), at which the amplitude (A) of the sound radiation of the third ultrasonic transducer (US3) is half the third amplitude maximum (A max3) of the sound radiation of the third ultrasonic transducer (US3) at its third resonant frequency (f 3), minus the third lower half maximum amplitude frequency (f 3u), at which the amplitude (A) of the sound radiation of the third ultrasound transducer (US3) is likewise half the third amplitude maximum (A max3) of the sound radiation of the third ultrasound transducer (US3) at its third resonant frequency (f 3).FIG. 6 shows a FIG. 6FIG. 6 shows, by way of example, in two extreme configurations, the superposition of a first amplitude spectrum in the form of a first spectral ultrasonic burst amplitude (A1) of a first ultrasonic transducer (US1) and a second amplitude spectrum in the form of a second spectral ultrasonic burst amplitude (A2) of a second ultrasonic transducer (US2) and a third amplitude spectrum in the form of a third spectral ultrasonic burst amplitude (A3) of a third ultrasonic transducer (US3).FIG. 6a is a schematic view of FIG. 6aIn FIG. 6 a, the frequency interval (Δf 12) between the first resonant frequency (f 1) of the first ultrasound transducer (US 1) and the second resonant frequency (f 2) of the second ultrasound transducer (US 12) is smaller than the first bandwidth (Δf 1) of the first ultrasound transducer (US 1).In addition, the frequency distance (Δf 12) between the first resonant frequency (f 1) of the first ultrasonic transducer (US1) and the second resonant frequency (f 2) of the second ultrasonic transducer (US12) is smaller than the second bandwidth (Δf 2) of the second ultrasonic transducer (US2).Furthermore, the frequency distance (Δf 12) between the first resonant frequency (f 1) of the first ultrasound transducer (US 1) and the second resonant frequency (f 2) of the second ultrasound transducer (US 2) is less than half the sum of the first bandwidth (Δf 1) of the first ultrasound transducer (US 1) and the second bandwidth (Δf 2) of the second ultrasound transducer (US 2)In FIG. 6 a, the frequency interval (Δf 23) between the second resonant frequency (f 2) of the second ultrasound transducer (US 2) and the third resonant frequency (f 3) of the third ultrasound transducer (US 3) is also smaller than the second bandwidth (Δf 2) of the second ultrasound transducer (US 2).In addition, the frequency interval (Δf 23) between the second resonant frequency (f 2) of the second ultrasonic transducer (US2) and the third resonant frequency (f 3) of the third ultrasonic transducer (US3) is smaller than the third bandwidth (Δf 3) of the third ultrasonic transducer (US3).Furthermore, the frequency distance (Δf 23) between the second resonant frequency (f 2) of the second ultrasound transducer (US2) and the third resonant frequency (f 3) of the third ultrasound transducer (US3) is less than half the sum of the second bandwidth (Δf 2) of the second ultrasound transducer (US2) and the third bandwidth (Δf 3) of the third ultrasound transducer (US3).In the example of FIG. 6 a, moreover, the first bandwidth (Δf 1) of the first ultrasound transducer (US 1) is approximately equal to the second bandwidth (Δf 2) of the second ultrasound transducer (US 2) and the third bandwidth (Δf 3) of the third ultrasound transducer (US 3).In the example of FIG. 6 a, the frequency interval (Δf 12) between the first resonant frequency (f 1) of the first ultrasound transducer (US 1) and the second resonant frequency (f 2) of the second ultrasound transducer (US 2) is approximately equal to the frequency interval (Δf 23) between the second resonant frequency (f 2) of the second ultrasound transducer (US 2) and the third resonant frequency (f 3) of the third ultrasound transducer (US 3).The advantage of selecting the parameters of the various ultrasound transducers lies in the possible combination of the three ultrasound transducers (US 1, US 2, US 3) which are exemplary here to form a single ultrasound transducer system of increased width. Instead of the ultrasonic transducers, ultrasonic transmitters can also be used in an analogous manner for transmitting and ultrasonic receivers for receiving ultrasonic bursts. That is to say that the transmission function can be separated from the reception function by apparatus. If instead of the ultrasonic transducers, ultrasonic receivers are used, the reception bandwidth of the overall system is also correspondingly distributed in an analogous manner, which enables many advantages.It is thus possible, for example, to emit an ultrasonic burst as an ultrasonic signal by means of such an ultrasonic sensor system (USS), the frequency bandwidth required of which fully uses the total frequency bandwidth (Δf g) of the ultrasonic sensor system (USS) having a plurality of ultrasonic transducers (US1, US2, US3). In this case, in the example of FIG. 6 a, the exemplary total frequency bandwidth (Δf g) of the ultrasonic sensor system (USS) comprising the first ultrasonic transducer (US 1) and the second ultrasonic transducer (US 2) and the third ultrasonic transducer (US 3) is greater than the first bandwidth (Δf 1) of the first ultrasonic transducer (US 1) and greater than the second bandwidth (Δf 2) of the second ultrasonic transducer (US 2) and greater than the third bandwidth (Δf 3) of the third ultrasonic transducer (US 3).This makes it possible for a first of the ultrasonic transducers to emit more than 50% of the sound energy at a first frequency at a first point in time during the emission of an ultrasonic burst and for a second of the ultrasonic transducers to emit less than 50% of the sound energy at this first frequency, while the first of the ultrasonic transducers emits less than 50% of the sound energy at a second frequency at a second point in time during the emission of the ultrasonic burst and for the second of the ultrasonic transducers to emit more than 50% of the sound energy at this second frequency. In this case, the first point in time and the second point in time are spaced apart from one another in time, and the first frequency differs from the second frequency.Conversely, in the case of a receive operation of the ultrasonic transducers, it becomes possible that at a first time during the reception of a reflected ultrasonic burst, a first of the ultrasonic transducers (US1) receives more than 50% of the receive amplitude at a first frequency and a second of the ultrasonic transducers (US2) receives less than 50% of the receive amplitude at this first frequency, while at a second time during the reception of the reflected ultrasonic burst, the first of the ultrasonic transducers (US1) receives less than 50% of the receive amplitude at a second frequency and the second of the ultrasonic transducers (US2) receives more than 50% of the receive amplitude at this second frequency. In this case, the first point in time and the second point in time are spaced apart from one another in time, and the first frequency differs from the second frequency.This makes it possible to transmit ultrasonic bursts with more complex coding and with a larger frequency bandwidth, which enables a substantially better increase in the signal-to-noise ratio and thus in the range. It is also possible to detect better resolved reflection signals of the ultrasonic bursts.FIG. 6b shows a schematic of FIG. 6bIn FIG. 6 b, the frequency interval (Δf 12) between the first resonant frequency (f 1) of the first ultrasound transducer (US 1) and the second resonant frequency (f 2) of the second ultrasound transducer (US 2) is greater than the first bandwidth (Δf 1) of the first ultrasound transducer (US 1).In addition, the frequency distance (Δf 12) between the first resonant frequency (f 1) of the first ultrasonic transducer (US1) and the second resonant frequency (f 2) of the second ultrasonic transducer (US2) is greater than the second bandwidth (Δf 2) of the second ultrasonic transducer (US2).Furthermore, the frequency distance (Δf 12) between the first resonant frequency (f 1) of the first ultrasound transducer (US 1) and the second resonant frequency (f 2) of the second ultrasound transducer (US 2) is greater than half the sum of the first bandwidth (Δf 1) of the first ultrasound transducer (US 1) and the second bandwidth (Δf 2) of the second ultrasound transducer (US 2)In FIG. 6 b, the frequency interval (Δf 23) between the second resonant frequency (f 2) of the second ultrasound transducer (US 2) and the third resonant frequency (f 3) of the third ultrasound transducer (US 3) is also greater than the second bandwidth (Δf 2) of the second ultrasound transducer (US 2).In addition, the frequency distance (Δf 23) between the second resonant frequency (f 2) of the second ultrasonic transducer (US2) and the third resonant frequency (f 3) of the third ultrasonic transducer (US3) is greater than the third bandwidth (Δf 3) of the third ultrasonic transducer (US3).Furthermore, the frequency distance (Δf 23) between the second resonant frequency (f 2) of the second ultrasound transducer (US2) and the third resonant frequency (f 3) of the third ultrasound transducer (US3) is greater than half the sum of the second bandwidth (Δf 2) of the second ultrasound transducer (US2) and the third bandwidth (Δf 3) of the third ultrasound transducer (US3).In the example of FIG. 6 b, moreover, the first bandwidth (Δf 1) of the first ultrasound transducer (US 1) is approximately equal to the second bandwidth (Δf 2) of the second ultrasound transducer (US 2) and the third bandwidth (Δf 3) of the third ultrasound transducer (US 3).In the example of FIG. 6 b, the frequency interval (Δf 12) between the first resonant frequency (f 1) of the first ultrasound transducer (US 1) and the second resonant frequency (f 2) of the second ultrasound transducer (US 2) is approximately equal to the frequency interval (Δf 23) between the second resonant frequency (f 2) of the second ultrasound transducer (US 2) and the third resonant frequency (f 3) of the third ultrasound transducer (US 3).If the parameters of the ultrasonic transducers (US1, US2, US3) are chosen in accordance with FIG. 6b, more complicated signals can be transmitted as well. However, continuous frequency sweep (chirp) is no longer possible, since considerable amplitude dips occur if the common excitation frequency (f A) of the ultrasonic transducers (US, US 2, US 3) lies in a frequency range between the amplitude spectra, here the three exemplary spectral ultrasonic burst amplitudes (A 1, A 2, A 3) of the exemplary three ultrasonic transducers (US 1, US 2, US 3). The corresponding amplitude dips of FIG. 6 aare considerably smaller.In principle, two basic operating modes are possible for such an ultrasonic sensor system: a) In the first operating mode, all ultrasonic transducers (US 1, US 2, US 3) are controlled with the same control signal (AS) and thus with the same control torque angular frequency (f A) and in phase-synchronous fashion. If the common activation torque input frequency (f A) is within the total frequency bandwidth (Δf g) of the ultrasonic sensor system (USS), at least one of the ultrasonic transmitters (US 1, US 2, US 3) oscillates. b) In the second operating mode, at least one of the ultrasonic transducers (US 1, US 2, US 3) is activated with a different activation signal (AS 1, AS 2, AS 3) and therefore typically no longer with the same activation torque input frequency (f A), but with a different activation torque input frequency (f A1, f A2, f A3) and not in phase-synchronous fashion.FIGS. 7 to 10FIGS. 7 to 10 show in principle possible types of a frequency sweep. In a frequency sweep, one or more ultrasonic transducers of the ultrasonic transducers (US1, US2, US2) are driven with a drive signal (AS) in which the drive torque input frequency (f A) is a function of time and changes during the transmission of an ultrasonic burst (UB) by this ultrasonic transducer. In the examples of FIGS. 7 to 10, various possible ultrasonic sweeps with a non-linear profile of the ultrasonic burst torque frequency (f m) are shown. The ultrasonic burst instantaneous frequency (f m) is directly linked to and typically follows the instantaneous frequency (f A) of the drive signal (AS) of the ultrasonic transducers (US1, US2, US3). In the examples of FIGS. 7 to 10, only a first ultrasonic transducer (US1) of the ultrasonic transducers (US1, US2, US3) is used for the transmission of the ultrasonic burst (UB), for example.FIG. 7 b shows the profile of the first spectral ultrasonic burst amplitude (A 1) of the first ultrasonic transducer (US 1) as a function of the actuation torque angular frequency (f A) in the vertical direction corresponding to FIG. 7 a.FIG. 7 ashows the first frequency profile (SF 1) of the ultrasonic burst torque input frequency (f m) of a first ultrasonic subbus of the drive signal for generating an ultrasonic burst (UB) by means of the first ultrasonic transducer (US 1). The first ultrasonic transducer (US1) has a first upper half maximum amplitude frequency (f 1o) and a first lower half maximum amplitude frequency (f 1u). At a first transmission start time (t 1s) in the example of FIG. 7 a, the first ultrasonic transducer (US 1) starts to transmit at an ultrasonic burst torque frequency (f m) corresponding to a first start frequency (f 1s) and to radiate sound. For this purpose, the first ultrasonic transmitter (US 1) is typically controlled with a control signal (AS) having a corresponding instantaneous first starting control frequency [f A1s]. At a first half-frequency time (t 1 / 50%) the first ultrasound transducer (US1) transmits at a first half-frequency (f 1 / 50%). For this purpose, the first ultrasonic transducer (US 1) is typically driven with a drive signal having a corresponding instantaneous first half-frequency drive frequency [f A1 / 50%]. At a first transmission end time (t 1e) in the example of FIG. 7 a, the first ultrasound transducer (US 1) stops the transmission process at a first end frequency (f 1e). For this purpose, typically at this first transmission end time (t 1e) the first ultrasonic transmitter (US 1) is driven with a drive signal having a corresponding instantaneous first end drive frequency [f A1e].The first half-frequency drive frequency [f A1 / 50%] is calculated as follows for the purposes of this specification:The first starting frequency (f 1s) naturally lies between the first upper half maximum amplitude frequency (f 1o) and the first lower half maximum amplitude frequency (f 1u).The first half-frequency (f 1 / 50%) is likewise between the first upper half-maximum amplitude frequency (f 1o) and the first lower half-maximum amplitude frequency (f 1u).The first final frequency (f 1e) is also between the first upper half maximum amplitude frequency (f 1o) and the first lower half maximum amplitude frequency (f 1u).In the example of FIG. 7, the ultrasonic burst duration (bd) is obtained as a time difference between the first transmission end time pulse (t 1e) minus the first transmission start time pulse (t 1s).The half-frequency time (t 1 / 50%), at which the drive signal of the first ultrasonic transducer (US1) has the half-frequency drive frequency [f A1 / 50%] or at which the transmission frequency of the sound radiation of the first ultrasonic transducer (US1) has the first half-frequency (f 1 / 50%) divides the burst duration (bd) into a first temporal burst phase (t 1a) and an immediately following second temporal burst phase (t 1b). It is proposed that the first burst phase (t 1a) is designed to be considerably different in terms of time length compared to the second burst phase (t 1b). As a result, the burst duration (bd) is divided into two time burst phases (t 1a, t 1b) which are not of equal length in time. Furthermore, it is proposed that the frequency profile of the ultrasonic burst torque frequency (f m) is monotone, preferably even strictly monotone, either falling or rising. The initial and final phase of the sound emission for switching on and off the first ultrasonic transducer (US 1) as an example here is not taken into account here in this monotonia condition for simplification, since naturally the switch-on process is always increasing (increasing from 0 Hz) and the switch-off process is always decreasing (decreasing to 0 Hz). In the example of FIG. 7 a, the frequency profile (SF 1) of the ultrasonic burst torque frequency (f m) of a first ultrasonic subburst is, for example, strictly monotonously decreasing and the first temporal burst phase (t 1a) is considerably shorter in time than the second temporal burst phase (t 1b).FIG. 8 shows an embodiment of FIG. 8FIG. 8 b corresponds to FIG. 7 b. Reference is made to the corresponding description.FIG. 8 a corresponds to FIG. 7 a, with the difference that the frequency profile (SF 1) of the ultrasonic burst torque frequency (f m) of a first ultrasonic subburst within an ultrasonic burst (UB) increases strictly monotonically by way of example and the first temporal burst phase (t 1a) is considerably shorter in time than the second temporal burst phase (t 1b).FIG. 9 shows a schematic of FIG. 9FIG. 9 b corresponds to FIG. 7 b. Reference is made to the corresponding description.FIG. 9 acorresponds to FIG. 7 a, with the difference that the frequency profile (SF 1) of the ultrasonic burst torque frequency (f m) of a first ultrasonic subburst within an ultrasonic burst (UB) increases, for example, strictly monotonically and the first temporal burst phase (t 1a) is considerably longer in time than the second temporal burst phase (t 1b).FIG. 10 shows a schematic view of FIG. 10FIG. 10 b corresponds to FIG. 7 b. Reference is made to the corresponding description.FIG. 10 acorresponds to FIG. 7 a, with the difference that the frequency profile (SF 1) of the ultrasonic burst torque frequency (f m) of a first ultrasonic subburst within an ultrasonic burst (UB) is, for example, strictly monotonically decreasing and the first temporal burst phase (t 1a) is considerably longer in time than the second temporal burst phase (t 1b).FIG. 11 shows a schematic of FIG. 11FIG. 11 shows an exemplary arrangement consisting of a first ultrasound transducer (US 1) and a second ultrasound transducer (US 2) and a third ultrasound transducer (US 3). In the example of FIG. 11, the ultrasonic transducers (US1, US2, US3) are arranged in an isosceles triangle, the edge lengths of which are smaller than twice the diameter of the sound emission surfaces of the ultrasonic transducers (US1, US2, US3). In the example of FIG. 11, the sound emission surfaces are, for example, circular and, for all three ultrasonic transducers (US 1, US 2, US 3), are, for example, of the same size. The first ultrasonic transducer (US1), when transmitting, transmits at a first ultrasonic burst torque frequency (f 1m). The second ultrasonic transducer (US2), when transmitting, transmits at a second ultrasonic burst torque frequency (f 2m). The third ultrasonic transducer (US3) when transmitting transmits at a third ultrasonic burst torque frequency (f 3m).The ultrasonic transducers (US1, US2, US3) are preferably arranged in an isosceles triangle, the edge lengths of which are smaller than ten times the diameter of the sound emission surfaces of the ultrasonic transducers (US1, US2, US3) and / or smaller than five times the diameter of the sound emission surfaces of the ultrasonic transducers (US1, US2, US3) and / or smaller than three times the diameter of the sound emission surfaces of the ultrasonic transducers (US1, US2, US3) and / or better smaller than twice the diameter of the sound emission surfaces of the ultrasonic transducers (US1, US2, US3).FIG. 12 shows a schematic view of FIG. 12FIG. 12 corresponds to FIG. 7 with the difference that a frequency sweep is now generated with the aid of three ultrasonic sensors (US 1, US 2, US 3).In the example of FIG. 12, all three ultrasonic transducers (US 1, US 2, US 3) are intended to be driven by the same drive signal with the same instantaneous drive frequency (f A) and therefore emit sound with the same ultrasonic burst torque input frequency (f 1m, f 2m, f 3m). In contrast to FIG. 11, in this respect, in the example of FIG. 12 all three exemplary ultrasonic transducers (US 1, US 2, US 3) transmit with a respective ultrasonic burst instantaneous frequency (f 1m, f 2m, f 3m) corresponding to the instantaneous drive frequency (f A) or not or only negligibly if the instantaneous drive frequency (f A) is just outside their respective bandwidth (Δf 1, Δf 2, Δf 3) of the respective ultrasonic transducer (US 1, US 2, US 3).The first ultrasonic transducer (US1) has a first spectral ultrasonic burst amplitude (A1) of the first ultrasonic transducer (US1).The second ultrasonic transducer (US2) has a second spectral ultrasonic burst amplitude (A2) of the second ultrasonic transducer (US2).The third ultrasound transducer (US3) has a third spectral ultrasound burst amplitude (A3) of the third ultrasound transducer (US3).These spectral ultrasonic burst amplitudes (A1, A2, A3) are intended here to correspond, by way of example, to the situation of the exemplary FIG. 6 a. Reference is expressly made here to the associated description of FIG. 6 a.In contrast to the transmission of the ultrasonic burst (UB) according to FIG. 7 a, ultrasonic burst instantaneous frequencies (f m) are now emitted which are outside the first bandwidth (Δf 1) of the first ultrasonic transducer (US 1). That is to say, the frequency bandwidth of the ultrasonic burst (UB) transmitted in FIG. 12 is considerably wider than the frequency bandwidth of the ultrasonic burst (UB) transmitted in FIG. 7a.It is important here that the first bandwidth (Δf 1) of the first ultrasound transducer (US1) overlaps with the second bandwidth (Δf 2) of the second ultrasound transducer (US2) and that the second bandwidth (Δf 2) of the second ultrasound transducer (US2) overlaps with the third bandwidth (Δf 3) of the third ultrasound transducer (US3).This now allows the first frequency profile (SF1) of the ultrasonic burst instantaneous frequency (f m) within the ultrasonic burst (UB) to follow any curve within the overall frequency bandwidth (Δf g) of the ultrasonic sensor system (USS), which is increased by the coupling of the first ultrasonic transducer (US1) and the second ultrasonic transducer (US2) and the third ultrasonic transducer (US3), when transmitted by means of the first ultrasonic transducer (US1) and the second ultrasonic transducer (US2) and the third ultrasonic transducer (US3). In this respect, FIG. 12 is only a particularly preferred profile of many profiles that become possible in this way.At a third transmission start time (t 3s) in the example of FIG. 12, the third ultrasound transducer (US3) starts to transmit an ultrasound subburst with a third start frequency (f 3s), which corresponds to a third excitation start frequency [f A3s] for the frequency of the excitation signal that drives the three ultrasound transducers (US1, US2, US3) together in the example of FIG. 12. The third ultrasonic transducer (US3) then radiates the ultrasonic burst at an ultrasonic burst instantaneous frequency (f m) which corresponds to the third starting frequency (f 3s) at this transmission starting time (t 3s). The third starting frequency (f 3s) is necessarily within the third bandwidth (Δf 3) of the third ultrasound transducer (US3). In the example of FIG. 12, the third starting frequency (f 3s) is outside the second bandwidth (Δf 2) of the second ultrasound transducer (US2) and outside the first bandwidth (Δf 1) of the first ultrasound transducer (US1). For the time duration of a third single-mode time (smt 3) therefore only the third ultrasound transducer (US 3) transmits. During this time interval of a third single-mode time (smt 3) significant excitation of the first ultrasound transducer (US 1) and of the second ultrasound transducer (US 2) with the instantaneous excitation frequency (f A) by means of the drive signal (AS) is not possible.In the example of FIG. 12, the drive device (AV) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the instantaneous drive frequency (f A) within the third single-mode time (smt 3). At a second transmission start time (t 2s) in the example of FIG. 12, the second ultrasound transducer (US2) likewise starts, in a fixed phase relationship to the transmission of the third ultrasound transducer (US3), with the transmission of an ultrasound signal at a second start frequency (f 2s), which corresponds to a second excitation start frequency [f A2s] for the frequency of the excitation signal which jointly controls the three ultrasound transducers (US1, US2, US3) in the example of FIG. 12. The third ultrasound transducer (US3) and the second ultrasound transducer (US2) radiate from this second transmission start time (t 2s) in phase synchronism with the same ultrasound burst moment frequency (f m) in this example. This begins with a first dual-mode time (dmt 23), in which the third ultrasound transducer (US3) and the second ultrasound transducer (US2) emit sound simultaneously.The drive device (AV) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the instantaneous drive frequency (f A) within the dual-mode time (dmt 23), in which the third ultrasonic transducer (US 3) and the second ultrasonic transducer (US 2) emit sound, in the example of FIG. 12. As a result, the ultrasonic burst torque frequency (f m) at which the third ultrasonic transducer (US3) and the second ultrasonic transducer (US2) emit sound, also falls further. At a third transmission end time (t 3e) in the example of FIG. 12, the third ultrasound transducer (US3) stops the transmission of its ultrasound signal at a third end frequency (f 3e), which corresponds to a third excitation end frequency [f A3e] for the excitation signal (AS) driving together three ultrasound transducers (US1, US2, US3) in the example of FIG. 12. Thus, in this example of FIG. 12, a second single-mode time (smt 2) in which only the second ultrasonic transducer (US2) emits sound, begins.In the example of FIG. 12, the drive device (AV) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously decreases the instantaneous drive frequency (f A) within the second single-mode time (smt 2) further. As a result, the ultrasonic burst torque frequency (f m), at which the second ultrasonic transducer (US2) emits sound, also falls further. At a first transmission start time (t 1s) in the example of FIG. 12, the first ultrasound transducer (US 1) likewise starts, in a fixed phase relationship to the transmission of the second ultrasound transducer (US 2), with the transmission of an ultrasound signal at a first start frequency (f 1s), which corresponds to a first excitation start frequency [f A1s] for the frequency of the three ultrasound transducers (US 1, US 2, US 3) in the example of FIG. 12 driving excitation signals jointly. The first ultrasound transducer (US1) and the second ultrasound transducer (US2) radiate from this first transmission start time (t 1s) in phase synchronism with the same ultrasound burst moment frequency (f m) in this example. This begins with a second dual-mode time (dmt 12), in which the first ultrasound transducer (US1) and the second ultrasound transducer (US2) emit sound.The drive device of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the instantaneous drive frequency (f A) within the dual-mode time (dmt 12), in which the first ultrasonic transducer (US 1) and the second ultrasonic transducer (US 2) emit sound, in the example of FIG. 12. As a result, the ultrasonic burst torque frequency (f m), at which the second ultrasonic transducer (US2) and the first ultrasonic transducer (US1) emit sound, also falls further.At a second transmission end time (t 2e) in the example of FIG. 12, the second ultrasound transducer (US2) stops the transmission of an ultrasound signal at a second end frequency (f 2e), which corresponds to a second excitation end frequency [f A2e] for the excitation signal driving together the frequency of the three ultrasound transducers (US1, US2, US3) in the example of FIG. 12. That is, at this time, the first ultrasonic transducer (US1) and the second ultrasonic transducer (US2) radiate sound at an ultrasonic burst instantaneous frequency (f m) corresponding to this second wide end frequency (f 2e). Thus, in this example of FIG. 12, a first single-mode time (smt 1) in which only the first ultrasonic transducer (US 1) emits sound, begins.In the example of FIG. 12, the drive device of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the instantaneous drive frequency (f A) within the first single-mode time (smt 1), in which only the first ultrasonic transducer (US 1) emits sound. As a result, the ultrasonic burst torque frequency (f m) at which the remaining first ultrasonic transducer (US1) still emits sound, also falls further. At a first transmission end time (t 1s) in the example of FIG. 12, the first ultrasonic transducer (US 1) stops the transmission of an ultrasonic signal at a first end frequency (f 1e), which corresponds to a first excitation end frequency [f A1e] for the frequency of the excitation signal driving the three ultrasonic transducers (US 1, US 2, US 3) together in the example of FIG. 12. That is, at this time, the first ultrasonic transducer (US1) radiates sound at an ultrasonic burst instantaneous frequency (f m) corresponding to this second wide end frequency (f 2e). Thus, in this example of FIG. 12, the transmission of the ultrasonic burst (US) and thus the burst duration (bd) ends. The sound radiation then terminates overall and the ultrasonic burst (UB) is terminated.FIG. 13 shows a schematic of FIG. 13FIG. 13 shows in simplified form and schematically an exemplary system for generating the exemplary frequency profile of FIG. 12 ; an ultrasonic sensor system (USS) corresponding to FIG. 11 is used in this case, for example. A control device (AV) can be part of the ultrasonic sensor system (USS) or can also be arranged outside the ultrasonic sensor system (USS).The control device (AV) generates one or more control signals (AS) which is here, for example, guided in parallel to a plurality of ultrasonic transducers (US 1, US 2, US 3). Thus, the ultrasonic transducers (US1, US2, US3) of the plurality of ultrasonic transducers (US1, US2, US3) are excited to oscillate at the same drive frequency (f A) of the drive signal (AS). However, the ultrasonic transducers (US1, US2, US3) only oscillate when the instantaneous drive frequency (f A) of the drive signal (AS) lies in their respective bandwidth (Δf 1, Δf 2, Δf 3).FIG. 14 shows a schematic of FIG. 14FIG. 14 corresponds in essential parts to FIG. 12, but now the excitation signal (AS) temporarily comprises more than one excitation frequency (f A). For example, the control signal (AS) can comprise a first excitation frequency (f A1) of a first excitation signal component and a second excitation frequency (f A2) of a second excitation signal component and a third excitation frequency (f A3) of a third excitation signal component. The first excitation signal component and the second excitation signal component and the third excitation signal component are then preferably superimposed by summation to form the actual excitation signal (AS).In the example of FIG. 14, first, in a first phase of the exemplary ultrasonic burst (UB), all three ultrasonic transducers (US1, US2, US3) are intended to be driven by way of example with the same drive signal (AS) with the same first drive torque angular frequency (f A1). In contrast to FIG. 11, in this respect, in the example of FIG. 14, all three exemplary ultrasonic transducers (US 1, US 2, US 3) transmit again with the frequencies corresponding to the activation torque frequencies (f A1, f A2) or not, or only negligibly, if the activation torque frequencies (f A1, f A2) are just outside their respective bandwidth (Δf 1, Δf 2, Δf 3).The first ultrasonic transducer (US1) has a first spectral ultrasonic burst amplitude (A1) of the first ultrasonic transducer (US1), as in FIG. 12.The second ultrasonic transducer (US2) has a second spectral ultrasonic burst amplitude (A2) of the second ultrasonic transducer (US2), as in FIG. 12.The third ultrasound transducer (US3) has a third spectral ultrasound burst amplitude (A3) of the third ultrasound transducer (US3), as in FIG. 12.These spectral ultrasonic burst amplitudes (A1, A2, A3) are intended here to correspond, as in FIG. 12, by way of example to the situation of the exemplary FIG. 6a. Reference is expressly made here to the associated description of FIG. 6 a.In contrast to the transmission of the ultrasonic burst (UB) according to FIG. 12, more than two ultrasonic burst moment frequencies within the transmitted ultrasonic burst are now transmitted temporarily in FIG. 14. That is to say that the frequency bandwidth of the ultrasonic burst (UB) transmitted in FIG. 14 is also considerably wider, at least temporarily, than the instantaneous frequency bandwidth of the ultrasonic burst (UB) transmitted in FIG. 12 during the burst duration (bd) of the ultrasonic burst (UB) in relation to individual transmission times.It is also important here that the first bandwidth (Δf 1) of the first ultrasound transducer (US1) overlaps with the second bandwidth (Δf 2) of the second ultrasound transducer (US2) and that the second bandwidth (Δf 2) of the second ultrasound transducer (US2) overlaps with the third bandwidth (Δf 3) of the third ultrasound transducer (US3).This now makes it possible for the first frequency profile (SF1) of the first excitation frequency (f A1) of a first signal component of the drive signal (AS) for generating an ultrasonic burst (UB) to follow any desired curve within the overall bandwidth thus increased by means of the first ultrasonic transducer (US1) and the second ultrasonic transducer (US2) and the third ultrasonic transducer (US3) as first ultrasonic subbursts within the ultrasonic burst (UB) and thus first frequency profile (SF1) of the ultrasonic instantaneous frequency (f m1). In this respect, FIG. 14 is only a particularly preferred course of many courses which become possible in this way.Furthermore, however, it is also possible that, in addition to the first frequency profile (SF1), a second frequency profile (SF2) of a second ultrasonic burst instantaneous frequency (f m2) of a second ultrasonic subburst within an ultrasonic burst (UB) and, if appropriate, a third frequency profile (SF3), not shown, of a third ultrasonic burst instantaneous frequency (f m3) of a third ultrasonic subburst within the ultrasonic burst (UB) follow any second curve or third curve, not shown, within the overall bandwidth thus increased, independently of the first frequency profile (SF1) of the first ultrasonic instantaneous frequency (f m1). In this respect, FIG. 14 is only a particularly preferred profile of many profiles and frequency profile combinations that become possible in this way. Also, theoretically n frequency characteristics, with n as a whole positive number, n ultrasonic burst instantaneous frequencies of ultrasonic subbursts within the ultrasonic burst (UB) can follow n arbitrary curves within the thus increased total bandwidth independently of the first frequency characteristic (SF1) of the first ultrasonic instantaneous frequency (f m1) ( f A1)At a third transmission start time (t 3s) in the example of FIG. 14, the third ultrasonic transducer (US 3) starts to transmit an ultrasonic signal with a third start frequency (f 3s) as the first ultrasonic torque input frequency (f m1), which corresponds to a third excitation start frequency [f A3s] for the first excitation frequency (f A1) of the excitation signals (AS) jointly driving three ultrasonic transducers (US 1, US 2, US 3) in the example of FIG. 14. The third starting frequency (f 3s) is within the third bandwidth (Δf 3) of the third ultrasound transducer (US3). In the example of FIG. 14, the third starting frequency (f 3s) is outside the second bandwidth (Δf 2) of the second ultrasonic transducer (US2) and outside the first bandwidth (Δf 1) of the first ultrasonic transducer (US1). For the time duration of a third single-mode time (smt 3) therefore only the third ultrasonic transducer (US 3) transmits at the first ultrasonic instantaneous frequency (f m1). During this period of time of a third single-mode time (smt 3) a significant excitation of the first ultrasound transducer (US 1) and of the second ultrasound transducer (US 2) with the instantaneous first excitation frequency (f A1) is not possible.In the example of FIG. 13, the drive device (AS) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the instantaneous first drive frequency (f A1) and thus the first ultrasonic torque input frequency (f m1) within the third single-mode time (smt 3). At a second transmission start time (t 2s) in the example of FIG. 14, the second ultrasonic transducer (US2) likewise starts, in a fixed phase relationship to the transmission of the third ultrasonic transducer (US3), with the transmission of an ultrasonic signal with a first ultrasonic instantaneous input frequency (f m1) at a second start frequency (f 2s), which corresponds to a second excitation start frequency [f A2s] for the instantaneous first drive frequency (f A1) of the excitation signal (AS) jointly driving three ultrasonic transducers (US1, US2, US3) in the example of FIG. 14. This begins with a dual-mode time (dmt 23), in which the third ultrasound transducer (US3) and the second ultrasound transducer (US2) emit sound at the first ultrasonic instantaneous frequency (f m1).In the example of FIG. 14, the drive device (AS) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the first instantaneous drive frequency (f A1) within the dual-mode time (dmt 23), in which the third ultrasonic transducer (US 3) and the second ultrasonic transducer (US 2) emit sound at the first ultrasonic instantaneous frequency (f m1). At a third transmission end time (t 3e) in the example of FIG. 14, the third ultrasonic transducer (US 3) stops the transmission of an ultrasonic signal with the first ultrasonic instantaneous input frequency (f m1) at a third end frequency (f 3e), which corresponds to a third excitation end frequency [f A3e] for the instantaneous first drive frequency (f A1) of the excitation signal (AS) jointly driving three ultrasonic transducers (US 1, US 2, US 3) in the example of FIG. 14. Thus, in this example of FIG. 14, a second single-mode time (smt 2) in which only the second ultrasonic transducer (US2) emits sound at the first ultrasonic instantaneous frequency (f m1) begins.In the example of FIG. 14, the control device (AS) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the instantaneous first control frequency (f A1) and thus the first ultrasonic instantaneous input frequency (f m1) within the second single-mode time (smt 2) further. At a first transmission start time (t 1s) in the example of FIG. 14, the first ultrasonic transducer (US 1) likewise starts, in a fixed phase relationship to the transmission of the second ultrasonic transducer (US 2), with the transmission of an ultrasonic signal of the first ultrasonic instantaneous input frequency (f m1) at a first start frequency (f 1s), which corresponds to a first excitation start frequency [f A1s] for the drive frequency (f A1) of the excitation signal (AS) jointly driving three ultrasonic transducers (US 1, US 2, US 3) in the example of FIG. 14. This begins a dual-mode time (dmt 12), in which the first ultrasound transducer (US1) and the second ultrasound transducer (US2) emit sound at the first ultrasonic instantaneous frequency (f m1) of sound.In the example of FIG. 14, the drive device (AS) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the instantaneous first drive frequency (f A1) and thus the first ultrasonic instantaneous frequency (f m1) within the dual-mode time (dmt 12), in which the first ultrasonic transducer (US 1) and the second ultrasonic transducer (US 2) emit sound at the first ultrasonic instantaneous frequency (f m1). At a second transmission end time (t 2e) in the example of FIG. 14, the second ultrasonic transducer (US2) stops the transmission of an ultrasonic signal with the first ultrasonic instantaneous input frequency (f m1) at a second end frequency (f 2e), which corresponds to a second excitation end frequency [f A2e] for the first drive frequency (f A1) of the excitation signal (AS) jointly driving three ultrasonic transducers (US1, US2, US3) in the example of FIG. 14. Thus, in this example of FIG. 14, a first single-mode time (smt 1) in which only the first ultrasonic transducer (US 1) emits sound at the first ultrasonic instantaneous frequency (f m1) begins.In the example of FIG. 14, the control device of the three ultrasonic transducers (US 1, US 2, US 3) then continuously lowers the instantaneous first control frequency (f A1) and thus the first ultrasonic instantaneous frequency (f m1) within the first single-mode time (smt 1), in which only the first ultrasonic transducer (US 1) emits sound at the first ultrasonic instantaneous frequency (f m1). At a first transmission end time (t 1e) in the example of FIG. 14, the first ultrasonic transducer (US 1) stops the transmission of the shared ultrasonic signal with the first ultrasonic instantaneous input frequency (f m1) at a first end frequency (f 1e), which corresponds to a first excitation end frequency [f A1e] for the instantaneous first drive frequency (f A1) of the excitation signal jointly driving the three ultrasonic transducers (US 1, US 2, US 3) in the example of FIG. 14. Thus, in this example of FIG. 12, the transmission of the ultrasonic burst (US) and thus the burst duration (bd) ends. The sound radiation then ends.In contrast to FIG. 12, at least for a temporal subsection of the burst duration (bd) parallel to the first ultrasound subburst with the first frequency profile (SF 1) of the first ultrasound instantaneous frequency (f m1) a second ultrasound burst component with a second frequency profile (SF 2) of the second ultrasound instantaneous frequency (f m2) is now superimposed, preferably by summation in the drive signal (AS). The control signal (AS) therefore typically has a first ultrasonic instantaneous frequency (f m1) as the first frequency component and a second ultrasonic instantaneous frequency (f m2) as the frequency components in the time segments of this superposition.In the example of FIG. 14, by way of example, in the first single-mode time (smt 1) by generating this second frequency profile (SF2) of the second ultrasonic burst instant frequency (f m2) of a second ultrasonic subburst within an ultrasonic burst (UB), it deviates from the structure of the ultrasonic burst of FIG. 12.At a further third transmission start time (t 3sb) in the example of FIG. 14, the third ultrasonic transducer (US3) begins to transmit an additional ultrasonic subburst at the third start frequency (f 3s) as a second ultrasonic torque input frequency (f m2), which again corresponds to the third excitation start frequency [f A3s] for the second excitation frequency (f A2) of the excitation signal (AS) jointly driving the three ultrasonic transducers (US1, US2, US3) in the example of FIG. 14. Starting from this point in time, the third transmission start point in time (t 3sb), the control signal (AS) therefore comprises not only a first ultrasonic subburst with a first ultrasonic torque input frequency (f m1), but also a second ultrasonic subburst with a second ultrasonic torque input frequency (f m2). The third starting frequency (f 3s) is typically within the third bandwidth (Δf 3) of the third ultrasound transducer (US3), as before. It is assumed here as unchanged by way of example. In the example of FIG. 14, the third starting frequency (f 3s) is outside the second bandwidth (Δf 2) of the second ultrasonic transducer (US2) and outside the first bandwidth (Δf 1) of the first ultrasonic transducer (US1). For the time duration of a third dual-mode time (dmt 13) in the example of FIG. 14, the third ultrasonic transducer (US3) emits a sound signal at a second ultrasonic instantaneous frequency (f m2) and the first ultrasonic transducer (US1) emits a sound signal at a first ultrasonic instantaneous frequency (f m1) in each case.Since the first instantaneous drive frequency (f A1) is below the third lower half maximum amplitude frequency (f 3u) in this third dual-mode time (dmt 13) the third ultrasonic transducer (US3) does not resonate at the first instantaneous drive frequency (f A1).Since the first instantaneous drive frequency (f A1) in this third dual-mode time (dmt 13) is also below the second lower half maximum amplitude frequency (f 2u) the second ultrasonic transducer (US2) also does not resonate at the first instantaneous drive frequency (f A1).Since the second instantaneous drive frequency (f A2) is above the second upper half maximum amplitude frequency (f 2o) in this third dual-mode time (dmt 13) the second ultrasonic transducer (US2) does not resonate at the second instantaneous drive frequency (f A2).Since the second instantaneous drive frequency (f A2) is above the first upper half maximum amplitude frequency (f 1o) in this third dual-mode time (dmt 13) the first ultrasonic transducer (US1) does not resonate at the second instantaneous drive frequency (f A2).During this period of time of a third dual-mode time (dmt 13) significant excitation of the first ultrasound transducer (US1) and of the second ultrasound transducer (US2) at the instantaneous second excitation frequency (f A2) is not possible.In this time period, which corresponds to a third dual-mode time (dmt 13), significant excitation of the third ultrasound transducer (US3) and the second ultrasound transducer (US2) at the instantaneous first excitation frequency (f A1) is not possible.In the example of FIG. 14, the control device (AS) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the instantaneous first control frequency (f A1) and thus the first ultrasonic torque input frequency (f m1) and the instantaneous second control frequency (f A2) and thus the second ultrasonic torque input frequency (f m2) together within the third dual-mode time (dmt 13). At a further second transmission start time (t 2sb) in the example of FIG. 14, the second ultrasonic transducer (US2) likewise starts, in a fixed phase relationship to the transmission of the third ultrasonic transducer (US3), with the transmission of an ultrasonic signal with the second ultrasonic instantaneous frequency (f m2) at a second start frequency (f 2s), which corresponds to a second excitation start frequency [f A2s] for the instantaneous second drive frequency (f A2) of the second signal component of the excitation signal (AS) jointly driving the three ultrasonic transducers (US1, US2, US3) in the example of FIG. 14. This begins a tri-mode time (tmt 123), in which the third ultrasonic transducer (US3) emits sound at the second ultrasonic instantaneous frequency (f m2) and the second ultrasonic transducer (US2) emits sound at the second ultrasonic instantaneous frequency (f m2) and the first ultrasonic transducer (US1) emits sound at the first ultrasonic instantaneous frequency (f m1).Since the first instantaneous drive frequency (f A1) is below the third lower half maximum amplitude frequency (f 3u) in this third dual-mode time (dmt 13) the third ultrasonic transducer (US3) does not resonate at the first instantaneous drive frequency (f A1).Since the first instantaneous drive frequency (f A1) in this third dual-mode time (dmt 13) is also below the second lower half maximum amplitude frequency (f 2u) the second ultrasonic transducer (US2) also does not resonate at the first instantaneous drive frequency (f A1).Since the second instantaneous drive frequency (f A2) in this third dual-mode time (dmt 13) is now below the second upper half maximum amplitude frequency (f 2o) and above the second lower half maximum amplitude frequency (f 2u) the second ultrasonic transducer (US2) now oscillates at the second instantaneous drive frequency (f A2) and emits sound at the second ultrasonic torque frequency (f m2).Since the second instantaneous drive frequency (f A2) is above the first upper half maximum amplitude frequency (f 1o) in this third dual-mode time (dmt 13) the first ultrasonic transducer (US1) does not resonate at the second instantaneous drive frequency (f A2) and emits sound of the first ultrasonic instantaneous drive frequency (f m1).During this time interval of a third tri-mode time (tmt 123) a significant excitation of the first ultrasound transducer (US1) with the instantaneous second excitation frequency (f A2) is not possible.During this time interval of a third tri-mode time (tmt 123) a significant excitation of the third ultrasound transducer (US3) and the second ultrasound transducer (US2) with the instantaneous first excitation frequency (f A1) is not possible.In the example of FIG. 14, the drive device (AS) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the first instantaneous drive frequency (f A1) and the second instantaneous drive frequency (f A2) and thus the first ultrasonic instantaneous drive frequency (f m1) and the second ultrasonic instantaneous drive frequency (f m2) within the tri-mode time (tmt 123), in which the third ultrasonic transducer (US 3) and the second ultrasonic transducer (US 2) and the first ultrasonic transducer (US 1) emit sound. At a further third transmission end time (t 3eb) in the example of FIG. 14, the third ultrasonic transducer (US3) stops the transmission of the ultrasonic signal with the second ultrasonic instantaneous frequency (f m2) at a third end frequency (f 3e), which corresponds to a third excitation end frequency [f A3e] for the instantaneous second drive frequency (f A2) of the excitation signal (AS) jointly driving the signal component of the three ultrasonic transducers (US1, US2, US3) in the example of FIG. 14. Thus, in this example of FIG. 14, a fourth dual-mode time (dmt 12b) in which only the second ultrasonic transducer (US2) emits sound at the second ultrasonic instantaneous frequency (f m2) and the first ultrasonic transducer (US1) emits sound at the first ultrasonic instantaneous frequency (f m1) begins.In the example of FIG. 14, the control device (AS) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously lowers the instantaneous first control frequency (f A1) and the instantaneous second control frequency (f A2) and thus the first ultrasonic torque input frequency (f m1) and the second ultrasonic torque input frequency (f m2) within the fourth dual-mode time (dmt 12b) further. At a first transmission start time (t 1s) in the example of FIG. 14, the first ultrasonic transducer (US 1) likewise starts, in a fixed phase relationship to the transmission of the second ultrasonic transducer (US 2), with the transmission of a second ultrasonic subburst of the ultrasonic signal at a first start frequency (f 1s), which corresponds to a first excitation start frequency [f A1s] for the second drive frequency (f A2) of the excitation signal (AS) jointly driving three ultrasonic transducers (US 1, US 2, US 3) in the example of FIG. 14. The particular thing here is that the first ultrasonic transducer (US1) must oscillate at two frequencies, at the first ultrasonic instantaneous frequency (f m1) and at the second ultrasonic instantaneous frequency (f m2), for this purpose. This is not always possible. As a rule, at this time, the instantaneous drive frequencies (f A1, f A2) will be so close together that the oscillation of the first ultrasound transducer (US1) floats.This begins a second tri-mode time (dmt 12), in which the first ultrasonic transducer (US1) emits sound at the first ultrasonic instantaneous frequency (f m1) and simultaneously at the second ultrasonic instantaneous frequency (f m2) and the second ultrasonic transducer (US2) emits sound at the second ultrasonic instantaneous frequency (f m2) and the first ultrasonic transducer oscillates at two ultrasonic instantaneous frequencies (f m1 and f m2).In the example of FIG. 14, the drive device (AS) of the three ultrasonic transducers (US 1, US 2, US 3) now continuously decreases the instantaneous first drive frequency (f A1) and the instantaneous second drive frequency (f A2) and thus the first ultrasonic torque input frequency (f m1) and the second ultrasonic torque input frequency (f m2) within the second tri-mode time (tmt 112), in which the first ultrasonic transducer (US 1) and the second ultrasonic transducer (US 2) emit sound. At a second transmission end time (t 2e) in the example of FIG. 14, the second ultrasonic transducer (US2) stops the transmission of an ultrasonic signal with the second ultrasonic instantaneous input frequency (f m2) at a second end frequency (f 2e), which corresponds to a second excitation end frequency [f A2e] for the second drive frequency (f A1) of the second signal component of the three ultrasonic transducers (US1, US2, US3) in the example of FIG. 14 and jointly drives the excitation signal (AS). Thus, in this example of FIG. 14, a last dual-mode time (dmt 11b), in which only the first ultrasound transducer (US1) emits sound, begins. In this case, the first ultrasonic transducer (US1) initially still oscillates at two ultrasonic instantaneous frequencies (f m1, f m2). In the end, in the example of FIG. 14, the frequency interval between the first ultrasonic instantaneous frequency (f m1) and the second ultrasonic instantaneous frequency (f m2) decreases until the two ultrasonic instantaneous frequencies (f m1, f m2) are ultimately the same in the example of FIG. 14.The drive device of the three ultrasonic transducers (US 1, US 2, US 3) thus continuously lowers the instantaneous first drive frequency (f A1) and the instantaneous second drive frequency (f A2) within the last dual-mode time (dmt 11b), in which only the first ultrasonic transducer (US 1) emits sound, in the example of FIG. 14. At a first transmission end time (t 1e) in the example of FIG. 14, the first ultrasonic transducer (US1) stops the transmission of the shared ultrasonic signal at a first end frequency (f 1e), that of a first frequency.The excitation end frequency [f A1e] for the instantaneous first drive frequency (f A1) and the instantaneous second drive frequency (f A2) of the excitation signal (AS) jointly driving three ultrasonic transducers (US 1, US 2, US 3) in the example of FIG. 14. Thus, in this example of FIG. 14, the transmission of the ultrasonic burst (US) and thus the burst duration (bd) ends. The sound radiation then ends.FIG. 15 shows a schematic of FIG. 15FIG. 15 shows in simplified form and schematically an exemplary system for generating the exemplary frequency profile of the following FIG. 16 ; an ultrasonic sensor system (USS) corresponding to FIG. 11 is used in this case, for example.In contrast to the system of FIG. 13, the first ultrasonic transducer (US 1) now has its own first drive device (AV 1). The second ultrasonic transducer (US2) now has its own second drive device (AV2). The third ultrasound transducer (US3) now has its own third drive device (AV3).The first drive device (AV1) drives the first ultrasonic transducer (US1) with the aid of a first drive signal (AS1).The second drive device (AV2) drives the second ultrasonic transducer (US2) with the aid of a second drive signal (AS2).The third drive device (AV 3) drives the third ultrasonic transducer (US 3) with the aid of a third drive signal (AS 3).A control unit (SG) controls the first drive device (AV 1) via a data bus (DB).The control unit (SG) controls the second drive device (AV 2) via the data bus (DB).The control unit (SG) controls the third drive device (AV 3) via the data bus (DB).The drive devices (AV 1, AV 2, AV 3) are preferably synchronized via the data bus. In this case, the drive devices (AV1, AV2, AV3) preferably contain their own time bases, i.e. for example clock generators or timers, which maintain the synchronization for a sufficiently long time without further synchronization signals of the control unit (SG).Thus, the ultrasonic transducers (US 1, US 2, US 3) of the plurality of ultrasonic transducers (US 1, US 2, US 3) can be excited to oscillate individually and independently at the same or different drive frequencies (f A1, f A2, f A3) of the drive signals (AS 1, AS 2, AS 3). However, the ultrasonic transducers (US 1, US 2, US 3) only oscillate in each case if the instantaneous drive frequencies (f A1, f A2, f A3) of the respective drive signals (AS 1, AS 2, AS 3) are in their respective associated bandwidth (Δf 1, Δf 2, Δf 3) respectively.FIG. 16 shows a schematic of FIG. 16FIG. 16 corresponds to FIG. 12 with the difference that a first frequency profile (SF1) of the first instantaneous excitation frequency (f A1) of a first signal component of the drive signal (AS) for generating an ultrasonic burst (UB) is now used together with a second frequency profile (SF2) of the second instantaneous excitation frequency (f A2) of a second signal component of the drive signal (AS) for generating an ultrasonic burst (UB), and together with a third frequency profile (SF3) of the third instantaneous excitation frequency (f A3) of a third signal component of the drive signal (AS) for generating an ultrasonic burst (UB). As a result, the ultrasonic sensor system (USS) radiates an ultrasonic signal at least temporarily, which comprises a first ultrasonic subburst having a first ultrasonic torque incident frequency (f m1) and a second ultrasonic subburst having a second ultrasonic torque incident frequency (f m2) and a third ultrasonic subburst having a third ultrasonic torque incident frequency (f m3) superimposed in a summed manner.The corresponding signal can be generated both by means of a device according to FIG. 15 and by means of a device according to FIG. 13.Since the first frequency profile (SF1) remains completely within the first bandwidth (Δf 1) of the first ultrasound transducer (US1), it is possible to generate this part of the ultrasound burst only with the first ultrasound transducer (US1), wherein the first ultrasound transducer is then driven with a first drive signal (AS1), which preferably then only comprises the first drive frequency (f A1). The first ultrasonic transducer (US1) then radiates a first ultrasonic subburst at the first ultrasonic instantaneous activation frequency (f m1) which corresponds to the first activation frequency (f A1).Since the second frequency profile (SF2) remains completely within the second bandwidth (Δf 2) of the second ultrasound transducer (US2), it is possible to generate this part of the ultrasound burst only with the second ultrasound transducer (US2), wherein the second ultrasound transducer is then driven with a second drive signal (AS2), which preferably then only comprises the second drive frequency (f A2). The second ultrasonic transducer (US2) then radiates a second ultrasonic subburst at the second ultrasonic instantaneous activation frequency (f m2) which corresponds to the second activation frequency (f A2).Since the third frequency profile (SF3) remains completely within the third bandwidth (Δf 3) of the third ultrasound transducer (US3), it is possible to generate this part of the ultrasound burst only with the third ultrasound transducer (US3), wherein the third ultrasound transducer is then driven with a third drive signal (AS3), which preferably then only comprises the third drive frequency (f A3). The third ultrasonic transducer (US3) then radiates a third ultrasonic subburst at the third ultrasonic instantaneous activation frequency (f m3) which corresponds to the third activation frequency (f A3).At a first transmission start time (t 1s) the first ultrasonic transducer (US1) starts to oscillate at the first start frequency (f 1s) as the first ultrasonic instantaneous frequency (f m1) and to emit its sound signal at this first ultrasonic instantaneous frequency (f m1). For this purpose, a control device (AV) or a first control device (AV1) controls the first ultrasonic transducer (US1) with a current first control frequency (f A1) which substantially corresponds to the desired first ultrasonic instantaneous frequency (f m1) of the sound radiation. In the example of FIG. 15, the control device (AV) or the first control device (AV1) decreases the instantaneous first control frequency (f A1) and thus the first ultrasonic instantaneous frequency (f m1) of the sound radiation of the first ultrasonic transducer (US1) as time progresses. At a first transmission end time (t 1e) the first ultrasound transducer (US1) then terminates the sound radiation at a first end frequency (f 1e) as the first ultrasound instantaneous frequency (f m1).At a second transmission start time (t 2s) the second ultrasonic transducer (US2) then starts to oscillate at the second start frequency (f 2s) as a second ultrasonic instantaneous frequency (f m2) and to emit its sound signal at this second ultrasonic instantaneous frequency (f m2). For this purpose, a control device (AV) or a second control device (AV2) controls the second ultrasonic transducer (US2) with a current second control frequency (f A2) which substantially corresponds to the desired second ultrasonic instantaneous control frequency (f m2). In the example of FIG. 15, the control device (AV) or the second control device (AV2) decreases the instantaneous second control frequency (f A2) and thus the second ultrasonic instantaneous frequency (f m2) of the sound radiation of the second ultrasonic transducer (US2) as time progresses. At a second transmission end time (t 2e) the second ultrasound transducer (US2) then terminates the sound radiation at a second end frequency (f 2e) as the second ultrasound instantaneous frequency (f m2).At a third transmission start time (t 3s) the third ultrasound transducer (US3) then starts to oscillate at the third start frequency (f 3s) as a third ultrasound instantaneous frequency (f m3) and to emit its sound signal at the third ultrasound instantaneous frequency (f m3). For this purpose, a control device (AV) or a third control device (AV3) controls the third ultrasonic transducer (US3) with a current third control frequency (f A3) which substantially corresponds to the desired current oscillation frequency. In the example of FIG. 15, the control device (AV) or the third control device (AV3) decreases the instantaneous third control frequency (f A3) and thus the third ultrasonic instantaneous frequency (f m3) of the sound radiation of the third ultrasonic transducer (US3) as time progresses. At a third transmission end time (t 3e) the third ultrasound transducer (US3) then terminates the sound radiation at a third end frequency (f 3e) as the third ultrasound instantaneous frequency (f m3).In the example of FIG. 16, the first starting time (t 1s) is earlier in time than the second starting time (t 2s) and the third starting time (t 3s). This results in a first single-mode time (smt 1), in which only the first ultrasonic transducer (US 1) emits sound at the first ultrasonic instantaneous frequency (f m1).In the example of FIG. 16, the second starting time (t 2s) is temporally after the first starting time (t 1s) and temporally before the third starting time (t 3s). This results in a first dual-mode time (dmt 1), in which only the first ultrasonic transducer (US1) with the first ultrasonic instantaneous frequency (f m1) and the second ultrasonic transducer (US2) with the second ultrasonic instantaneous frequency (f m2) emit sound with different ultrasonic instantaneous frequencies (f m1, f m2).After the third starting time (t 3s) the third ultrasound transducer (US3) then also starts to emit sound at the third ultrasound instantaneous frequency (f m3). Thus, in a time period beginning with the third starting time (t 3s) and ending with the first ending time (t 1e) a first tri-mode time (tmt) results in which all three ultrasonic transducers (US1, US2, US3) emit sound with three different frequencies from one another. The first ultrasonic transducer (US1) emits sound at the first ultrasonic instantaneous frequency (f m1). The second ultrasonic transducer (US2) emits sound at the second ultrasonic instantaneous frequency (f m2). The third ultrasonic transducer (US3) emits sound at the third ultrasonic instantaneous frequency (f m3).In the example of FIG. 16, the first end time (t 1e) is earlier in time than the second end time (t 2e) and the third end time (t 3e). This results in a second dual-mode time (dmt 2), in which only the second ultrasonic transducer (US2) emits sound at the second ultrasonic instantaneous frequency (f m2) and the third ultrasonic transducer (US3) emits sound at the third ultrasonic instantaneous frequency (f m3). The second dual-mode time (dmt 2) ends with the second end time (t 2e).In the example of FIG. 16, the second end time (t 2e) is temporally after the first end time (t 1e) and temporally before the third end time (t 3e). This results in a second single-mode time (smt 2), in which only the third ultrasonic transducer (US 3) emits sound at the third ultrasonic instantaneous frequency (f m3). The second single-mode time (smt 2) ends with the third end time (t 3e). This is then also the end of the ultrasonic burst.FIG. 17 shows a schematic of FIG. 17FIG. 17 corresponds to FIG. 12 with the difference, a first frequency profile (SF1) of the first ultrasonic instantaneous frequency (f m1) of a first ultrasonic subburst corresponding to the frequency profile of the first instantaneous excitation frequency (f A1) of a first signal component of the drive signal (AS) for generating an ultrasonic burst (UB), together with a second frequency profile (SF2) of the second ultrasonic instantaneous frequency (f m2) of a second ultrasonic subburst corresponding to the second instantaneous excitation frequency (f A2) of a second signal component of the drive signal (AS) for generating an ultrasonic burst (UB), and together with a third frequency profile (SF3) of the third ultrasonic instantaneous frequency (f m3) corresponding to the third instantaneous excitation frequency (f A3) of a third signal component of the drive signal (AS), can be used to generate an ultrasonic burst (UB). In contrast to the preceding FIG. 16, all frequency characteristics (SF 1, SF 2, SF 3) now end at a common end frequency (f e) as the respective ultrasonic torque input frequency (f m1, f m2, f m3) at a common end time (t e). Here, this common final frequency (f e) is chosen such that it can be generated by all the exemplary three ultrasonic transducers (US1, US2, US3). Two of the frequency profiles here are, for example, monotonically decreasing, one monotonically increasing.Figure 18 & Figure 19The sound radiation of the ultrasonic sensor system (USS) corresponds to a multipole development of a spherical spherical wave function, ignoring the distance between the ultrasonic sensors (US1, US2, US3) and the dimensions of the ultrasonic sensor system (USS). That is to say that the sound radiation lobe of an ultrasonic transducer (US1, US2, US3) of the ultrasonic sensor system (USS) has in each case an opening angle. The sound radiation lobe of an ultrasonic sensor has a lobe axis. If the sound radiation lobe is cut perpendicularly to the lobe axis in a sectional surface, the intensity distribution of the sound in this sectional surface is usually not distributed rotationally symmetrically around the point of penetration of the lobe axis through this sectional plane, but is usually rather elliptical. The opening angle of the sound radiation of an ultrasonic sensor in the vertical is often different from the opening angle of the sound radiation in the horizontal. In FIG. 18, the opening angles in the horizontal are denoted by the index H and the opening angles in the vertical are denoted by the index V. FIG. 18 a outlines the situation in plan view. FIG. 18 b outlines the situation in the side view.The sound radiation lobe of the first ultrasonic transducer (US1) of the ultrasound system (USS) has the vertical aperture angle α V and the horizontal aperture angle α H.The sound radiation lobe of the second ultrasonic transducer (US2) of the ultrasound system (USS) has the vertical aperture angle β V and the horizontal aperture angle β H.The sound radiation lobe of the third ultrasonic transducer (US3) of the ultrasound system (USS) has the vertical aperture angle γ V and the horizontal aperture angle γ H.In the example of FIG. 18, the aperture angles of the first ultrasound transducer (US 1) are designed to be larger than the aperture angles of the second ultrasound transducer (US 2) and larger than the aperture angles of the third ultrasound transducer (US 3), for example.In the example of FIG. 18, the aperture angles of the second ultrasound transducer (US2) are designed to be smaller than the aperture angles of the first ultrasound transducer (US1) and larger than the aperture angles of the third ultrasound transducer (US3).The different aperture angles can be designed, for example, by the diaphragm size in comparison with the acoustic wavelength. The resonant frequencies can be adjusted by material selection and material thickness. The selection of the excitation frequency (f A1, f A2, f A3) of the respective ultrasonic transducer (US1, US2, US3) also changes the dimensions of the radiation lobe.This now has the advantage that, at different excitation frequencies, the reflections of objects (O 1, O 2) that are at the same distance from the ultrasound system (see also FIG. 19 ) differ by the spectral composition of the reflected signal. In this way, an angle determination is possible.FIG. 20 shows a FIG. 20FIG. 20 illustrates how the different modulation types described above can now be used when approaching an important object (O), for example an obstacle.In the example of FIG. 20, the burst duration (bd) is shortened as the object (O) approaches.The number of simultaneously transmitted frequency characteristics (SF1, SF2, SF3) is increased from two to three when a distance between the ultrasonic sensor system (USS) and the object (O, O1, O2) is undershot. The number of simultaneously transmitted frequency characteristics (SF 1, SF 2, SF 3) thus changes as the object (O) approaches. Within an ultrasonic burst, the number of frequency characteristics is first increased from 1 to 2. With a greater approximation, the number of frequency characteristics is then increased from 1 to 3 within an ultrasonic burst.In the example of FIG. 20, the frequency characteristics are all strictly monotone within an ultrasonic burst, with the rate of drop of the ultrasonic instantaneous frequencies (f m1, f m2, f m3) and thus of the excitation frequencies (f A) falling within an ultrasonic burst (UB). The starting frequency (f 1s) of the first frequency profile (SF1) within an ultrasonic burst (UB) is changed as the object (O) approaches. First, the starting frequency (f 1s) of the first frequency profile (SF1) within an ultrasonic burst is increased with approach to the object (O) in order then to drop again with further approach. In the example of FIG. 20, all ultrasonic bursts have a single-mode time (smt), in which only the ultrasonic subburst with the first frequency profile (SF1) is transmitted. A time interval of the transmission of the ultrasonic burst (UB) has a dual-mode time (dmt), in which only the ultrasonic subbursts with the first frequency profile (SF1) and with the second frequency profile (SF3) are transmitted. Another part of the ultrasonic bursts has a tri-mode time (tmt), in which the ultrasonic sub-bursts are transmitted with the first frequency profile (SF1) and with the second frequency profile (SF3) and with the third frequency profile (SF3)FIG. 21 shows 21FIG. 21 illustrates the situation when using two ultrasonic sensor systems (USS1, USS2).In this example, for purposes of explanation, each alone of the exemplary two ultrasonic sensor systems (USS1, USS2) corresponds approximately to the exemplary ultrasonic sensor system (USS) of FIG. 11.Each of the ultrasonic sensor systems (USS1, USS2) receives three different ultrasonic reflection signals with different ultrasonic moment frequencies (f m1, f m2, f m3). when using different aperture angles according to FIG. 18 and different ultrasonic moment frequencies (f m1, f m2, f m3) within an ultrasonic sensor system. These received ultrasonic reflection signals, which are three by way of example, can already be evaluated in the ultrasonic sensor system (USS1, USS2) and then be transmitted to a control unit (SG) or else be analyzed unvaluated and compressed to the greatest possible extent unprocessed, transmitted to a control unit (SG), and then evaluated in the control unit (SG). Depending on the distance (s 1, s 2) of the object (O) from the respective ultrasonic sensor system (USS 1, USS 2), the ultrasonic reflection signal arrives at the respective ultrasonic sensor system (USS 1, USS 2) at different times, which can likewise be evaluated.FIG. 22Figure 22 shows the effect of the various ultrasound bursts on their Doppler resistance.FIG. 22 shows four examples of the influence of the ultrasonic Bust frequency bandwidth and the frequency modulation curvature on Doppler-related range errors at a travel speed of 8 m s -1. The top row shows spectrograms of four ultrasonic burst echo pairs. The lower row shows the envelopes of the associated cross correlation (CCF) function between the transmitted ultrasonic burst signal of the moving vehicle and the signal reflected by a stationary object after receipt by the ultrasonic sensor system located in the moving vehicle. The arrows indicate the actual time delay of 8 ms between the transmission time and the reception time of the echo. The vertical lines show the position of the peak in the CCF signal.As can easily be seen, a greater broadband nature of the ultrasonic burst leads to a reduction in the Doppler error.For the frequency measurement of simultaneously present frequenciesFor clarity, it is briefly mentioned how to measure the presence of multiple frequencies at a time.Samples of the signal to be evaluated are stored continuously as memory values. The storage values can always be assigned a storage time. The memory values are multiplied by a window signal. This can be, for example, one of the following window signals: rectangular window, von Hanning window, Hamming window, Blackman window, Blackman-Harris window, Blackman-Nuttall window, flat top window, Bartalt window, Bartalt-Hann window, cosine window, Tukey window, Lanczos window, Kaiser window, Gaussian window. Further window types are conceivable. The window function has a reference time. The time length of the relevant window should be smaller than the ultrasonic burst duration (bd). Preferably, the time length of the relevant window should be less than 1 / 10 of the ultrasonic burst duration (bd). The memory values are multiplied by the window function for the relevant reference time. In this case, a storage value is always multiplied by the value of the window signal to form a windowed sample value, the time point of which within the window signal corresponds to the sampling time point of the storage value taking into account the reference time point. The windowed samples then yield a windowed signal which may be subjected to a Fourier transform or a Z-transform. If a plurality of frequencies then appear in the transformed signal, a plurality of frequencies are present in the signal at the reference time. The reference time is shifted and the same analysis repeated again and again. The procedure is known as time-frequency analysis (TFA).List of reference charactersA ultrasound burst amplitude; A1 first spectral ultrasound burst amplitude of the first ultrasound transducer (US1); A2 second spectral ultrasound burst amplitude of the second ultrasound transducer (US2); A3 third spectral ultrasound burst amplitude of the third ultrasound transducer (US3); A max1 first amplitude maximum (A max1) of the sound radiation of the first ultrasound transducer (US1) at its first resonant frequency (f 1). The first amplitude maximum (A max1) of the sound radiation can be measured by exciting the first ultrasonic transducer (US1) with a first excitation frequency (f A1) whereby the first excitation frequency (f A1) is tuned and that first excitation frequency (f A1) is determined at which the first ultrasonic transmitter (US1) takes up the maximum active power. The sound power emitted in this case is understood in this document as the first amplitude maximum (A max1) of the sound radiation of the first ultrasonic transducer (US 1; A max2 second amplitude maximum (A max2) of the sound radiation of the second ultrasonic transducer (US 2) at its second resonant frequency (f 2). The second amplitude maximum (A max2) of the sound radiation can be measured by exciting the second ultrasonic transducer (US2) with a second excitation frequency (f A2) whereby the second excitation frequency (f A2) is tuned and that second excitation frequency (f A2) is determined at which the second ultrasonic transmitter (US2) takes up the maximum active power. The sound power emitted in this case is understood in this document as the second amplitude maximum (A max2) of the sound radiation of the second ultrasonic transducer (US2); A max3 third amplitude maximum (A max3) of the sound radiation of the third ultrasonic transducer (US3) at its third resonant frequency (f 3). The third amplitude maximum (A max3) of the sound radiation can be measured by exciting the third ultrasonic transducer (US3) with a third excitation frequency (f A3) whereby the third excitation frequency (f A3) is tuned and that third excitation frequency (f A3) is determined at which the third ultrasonic transmitter (US3) takes up the maximum active power. The sound power emitted in this case is understood in this document as the third amplitude maximum (A max3) of the sound emission of the third ultrasound transducer (US 3); AS drive signal; AS 1 first drive signal of the first ultrasound transducer (US 1); AS 2 first drive signal of the second ultrasound transducer (US 2); AS 3 first drive signal of the third ultrasound transducer (US 3); AV drive device; AV 1 first drive device of the first ultrasound transducer (US 1); AV 2 second drive device of the second ultrasound transducer (US 2); AV 3 third drive device of the third ultrasound transducer (US 3); bd burst duration of an ultrasound burst. The burst duration begins with the ultrasound burst start (UBS) and ends with the ultrasound burst end (UBE); D object distance between the next relevant object and the ultrasound measurement system; Δf 1 first bandwidth of the first ultrasound transducer (US1). The first bandwidth is the first upper half maximum amplitude frequency (f 1o), at which the amplitude (A) of the sound radiation of the first ultrasound transducer (US1) is half the first amplitude maximum (A max1) of the sound radiation of the first ultrasound transducer (US1) at its first resonant frequency (f 1) minus the first lower half maximum amplitude frequency (f 1u), wherein the amplitude (A) of the sound radiation of the first ultrasound transducer (US1) is likewise half the first amplitude maximum (A max1) of the sound radiation of the first ultrasound transducer (US1) at its first resonant frequency (f 1) ; Δf 12 frequency spacing between the first resonant frequency (f 1) of the first ultrasound transducer (US1) and the second resonant frequency (f 2) of the second ultrasound transducer (US2); Δf 2 second bandwidth of the second ultrasound transducer (US2). The second bandwidth is the second upper half maximum amplitude frequency (f 2o), at which the amplitude (A) of the sound radiation of the second ultrasound transducer (US2) is half the second amplitude maximum (A max2) of the sound radiation of the second ultrasound transducer (US2) at its second resonant frequency (f 2) minus the second lower half maximum amplitude frequency (f 2u), wherein the amplitude (A) of the sound radiation of the second ultrasound transducer (US2) is likewise half the second amplitude maximum (A max2) of the sound radiation of the second ultrasound transducer (US2) at its second resonant frequency (f 2) ; Δf 23 frequency spacing between the second resonant frequency (f 2) of the second ultrasound transducer (US2) and the third resonant frequency (f 3) of the third ultrasound transducer (US3); Δf 3 third bandwidth of the third ultrasound transducer (US3). The third bandwidth is the third upper half maximum amplitude frequency (f 3o), at which the amplitude (A) of the sound radiation of the third ultrasound transducer (US3) is half the third amplitude maximum (A max3) of the sound radiation of the third ultrasound transducer (US3) at its third resonant frequency (f 3) minus the third lower half maximum amplitude frequency (f 3u), wherein the amplitude (A) of the sound radiation of the third ultrasound transducer (US3) is likewise half the third amplitude maximum (A max3) of the sound radiation of the third ultrasound transducer (US3) at its third resonant frequency (f 3) ; Δf g total frequency bandwidth of the ultrasound sensor system (USS); dmt 12 second dual-mode time in FIG. 12, in which the first ultrasound transducer (US1) and the second ultrasound transducer (US2) emit sound; The method of measuring the intensity of the third ultrasound transducer (US3) and the second ultrasound transducer (US2) emit sound; f 1 the first resonant frequency of the first ultrasound transducer (US1). The first resonant frequency of the first ultrasonic transducer (US1) is determined in the sense of this document such that the first amplitude maximum (A max1) of the sound radiation of the first ultrasonic transducer (US1) is sought by detuning the first excitation frequency (f A1) of the first ultrasonic transducer (US1) with preferably at least locally constant excitation amplitude of the first excitation signal (AS1) of the first ultrasonic transducer (US1). The first amplitude maximum (A max1) can be measured by exciting the first ultrasonic transducer (US1) with a first excitation frequency (f A1) whereby the first excitation frequency (f A1) is tuned and the first excitation frequency (f A1) is determined at which the first ultrasonic transmitter (US1) takes up the maximum active power. The sound power emitted in this case is understood in this document as the first amplitude maximum (A max1) of the sound emission of the first ultrasonic transducer (US 1). The first excitation frequency (f A1) at which this first amplitude maximum (A max1) occurs, is the first resonant frequency of the first ultrasonic transducer (US2); f 1 / 50% is the first half frequency. The first half-frequency results as f 1 / 50%=( f 1s- f 1e) / 2+ f 1e; f 1e first final frequency; f 1m first ultrasonic burst moment frequency at which the first ultrasonic transmitter (US1) emits sound; f 1o first upper half-maximum amplitude frequency (f 1o). At the first upper half maximum amplitude frequency (f 1o) the amplitude (A) of the sound radiation of the first ultrasound transducer (US1) is half of the first amplitude maximum (A max1) of the sound radiation of the first ultrasound transducer (US1) at its first resonant frequency (f 1). The first upper half maximum amplitude frequency (f1o) of the first ultrasound transducer (US1) is above the first resonant frequency (f) of the first ultrasound transducer (US1); fersth starting frequency; fersth lower half maximum amplitude frequency (f). At the first lower half maximum amplitude frequency (f1u), the amplitude (A) of the sound radiation of the first ultrasonic transducer (US 1) is half of the first amplitude maximum (Amax1) of the sound radiation of the first ultrasonic transducer (US 1) at its first resonant frequency (f1). The first lower half maximum amplitude frequency (f1u) of the first ultrasound transducer (US 1) is below the first resonant frequency (f1) of the first ultrasound transducer (US 1); f2zwide resonant frequency of the second ultrasound transducer (US 2). The second resonant frequency of the second ultrasonic transducer (US2) is determined in the sense of this document such that the second amplitude maximum (Amax2) of the sound radiation of the second ultrasonic transducer (US2) is sought by detuning the second excitation frequency (fA2) of the second ultrasonic transducer (US2) with preferably at least locally constant excitation amplitude of the second excitation signal of the second ultrasonic transducer (US2). The second amplitude maximum (Amax2) can be measured by exciting the second ultrasonic transducer (US2) with a second excitation frequency (fA2), wherein the second excitation frequency (fA2) is tuned and that second excitation frequency (fA2) is determined at which the second ultrasonic transmitter (US2) takes up the maximum active power. The sound power emitted in this case is understood in this document as the second amplitude maximum (Amax2) of the sound emission of the second ultrasonic transducer (US2). The second excitation frequency (fA2) at which this second amplitude maximum (Amax2) occurs is the second resonant frequency of the second ultrasound transducer (US2); f2 / 50%zwide half-frequency. The second half-frequency results as f2 / 50%=(f2s-f2e) / 2+f2e ; f2ezweite final frequency; f2mzweite ultrasonic burst moment frequency at which the second ultrasonic transmitter (US2) emits sound; f2ozweite upper half-maximum amplitude frequency (f2o ). At the second upper half maximum amplitude frequency (f2o), the amplitude (A) of the sound radiation of the second ultrasound transducer (US2) is half of the second amplitude maximum (Amax2) of the sound radiation of the second ultrasound transducer (US2) at its second resonant frequency (f2 ). The second upper half maximum amplitude frequency (f2o) of the second ultrasound transducer (US2) is above the second resonant frequency (f2) of the second ultrasound transducer (US2); f2szweite starting frequency; f2uzweite lower half maximum amplitude frequency (f2u ). At the second lower half maximum amplitude frequency (f2u), the amplitude (A) of the sound radiation of the second ultrasound transducer (US2) is half the second amplitude maximum (Amax2) of the sound radiation of the second ultrasound transducer (US2) at its second resonant frequency (f2). The second lower half maximum amplitude frequency (f2u) of the second ultrasound transducer (US2) is below the second resonant frequency (f2) of the second ultrasound transducer (US2); f3dritte resonant frequency of the third ultrasound transducer (US3). The third resonant frequency of the third ultrasound transducer (US3) is determined in the sense of this document such that the third amplitude maximum (Amax3 ) of the sound radiation of the third ultrasound transducer (US3) is sought by detuning the third excitation frequency (fA3 ) of the third ultrasound transducer (US3) with preferably at least locally constant excitation amplitude of the third excitation signal of the third ultrasound transducer (US3). The third amplitude maximum (Amax3) can be measured by exciting the third ultrasonic transducer (US3) with a third excitation frequency (fA3), wherein the third excitation frequency (fA3) is tuned and that third excitation frequency (fA3) is determined at which the third ultrasonic transmitter (US3) takes up the maximum active power. The sound power emitted in this case is understood in this document as the third amplitude maximum (Amax3) of the sound emission of the first ultrasonic transducer (US1). The third excitation frequency (fA3) at which this third amplitude maximum (Amax3) occurs is the third resonant frequency of the third ultrasound transducer (US3); f3 / 50%dritte half frequency. The third half-frequency results as f3 / 50%=(f3s-f3e) / 2+f3e ; f3edritte final frequency; f3mdritte ultrasonic burst moment frequency at which the third ultrasonic transmitter (US3) emits sound; f3odritte upper half-maximum amplitude frequency (f3o ). At the third upper half maximum amplitude frequency (f3o), the amplitude (A) of the sound radiation of the third ultrasound transducer (US3) is half the third amplitude maximum (Amax3) of the sound radiation of the third ultrasound transducer (US3) at its third resonant frequency (f3). The third upper half maximum amplitude frequency (f3o) of the third ultrasound transducer (US3) is above the third resonant frequency (f3) of the third ultrasound transducer (US3); f3sdritte starting frequency; f3udritte lower half maximum amplitude frequency (f3u ). At the third lower half maximum amplitude frequency (f3u), the amplitude (A) of the sound radiation of the third ultrasound transducer (US3) is half the third amplitude maximum (Amax3) of the sound radiation of the third ultrasound transducer (US3) at its third resonant frequency (f3). The third lower half maximum amplitude frequency (f3u) of the third ultrasound transducer (US3) is below the third resonant frequency (f3) of the third ultrasound transducer (US3); fAAnsteuermomentanfrequenz; fA1erste drive frequency of the first ultrasound transducer (US1); fA1 / 50%erste half frequency drive frequency; fA1eerste final drive frequency; fA1serste starting drive frequency; fA2zweite drive frequency of the second ultrasound transducer (US2); fA2 / 50%zweite half-frequency drive frequency; fA2ezweite end drive frequency; fA2szweite start drive frequency; fA3dritte third ultrasonic transducer (US3) drive frequency; fA3 / 50%dritte half-frequency drive frequency; fA3edritte end drive frequency; fA3sdritte start drive frequency; fmUltraschallburstmomentanfrequenz; fm,0nullte ultrasonic instantaneous frequency of the zeroth ultrasonic pulse (P0) in the zeroth ultrasonic period with the zeroth ultrasonic period duration (T0) within an ultrasonic burst (UB); fm,1erste ultrasonic instantaneous frequency of the first ultrasonic pulse (P1) in the first ultrasonic period with the first ultrasonic period duration (T1) within an ultrasonic burst (UB); fm,2zweite ultrasonic instantaneous frequency of the second ultrasonic pulse (P2) in the second ultrasonic period with the second ultrasonic period duration (T2) within an ultrasonic burst (UB); fm,3dritte ultrasonic instantaneous frequency of the third ultrasonic pulse (P3) in the third ultrasonic period with the third ultrasonic period duration (T3) within an ultrasonic burst (UB); fm,4vated ultrasonic instantaneous frequency of the fourth ultrasonic pulse (P4) in the fourth ultrasonic period with the fourth ultrasonic period duration (T4) within an ultrasonic burst (UB); fm,5fünfte ultrasonic instantaneous frequency of the fifth ultrasonic pulse (P5) in the fifth ultrasonic period with the fifth ultrasonic period duration (T5) within an ultrasonic burst (UB); fm,6sechste ultrasonic instantaneous frequency of the sixth ultrasonic pulse (P6) in the sixth ultrasonic period with the sixth ultrasonic period duration (T6) within an ultrasonic burst (UB); fm,7siebte ultrasonic instantaneous frequency of the seventh ultrasonic pulse (P7) in the seventh ultrasonic period with the seventh ultrasonic period duration (T7) within an ultrasonic burst (UB); fm,jj-th ultrasonic instantaneous frequency of the j-th ultrasonic pulse (Pj) in the j-th ultrasonic period with the j-th ultrasonic period duration (Tj) within an ultrasonic burst (UB) (here j stands for an integer positive number); O object; O1 first object; O2 second object; P0nullter ultrasonic pulse in the zeroth ultrasonic period of the exemplary ultrasonic burst (UB) of FIG. 2 a; P1erster ultrasonic pulse in the first ultrasonic period of the exemplary ultrasonic burst (UB) of FIG. 2 a; P2zweiter ultrasonic pulse in the second ultrasonic period of the exemplary ultrasonic burst (UB) of FIG. 2 a; P3dritter ultrasonic pulse in the third ultrasonic period of the exemplary ultrasonic burst (UB) of FIG. 2 a; P4vierter ultrasonic pulse in the fourth ultrasonic period of the exemplary ultrasonic burst (UB) of FIG. 2 a; P5fünfter ultrasonic pulse in the fifth ultrasonic period of the exemplary ultrasonic burst (UB) of FIG. 2 a; P6sechster ultrasonic pulse in the sixth ultrasonic period of the exemplary ultrasonic burst (UB) of FIG. 2 a; P7siebter ultrasonic pulse in the seventh ultrasonic period of the exemplary ultrasonic burst (UB) of FIG. 2 a; Pjj-th ultrasonic pulse in the j-th ultrasonic period of the exemplary ultrasonic burst (UB) (here j stands for an integer positive number); SF1 first frequency profile of the ultrasonic burst instantaneous frequency (fm) or of the first ultrasonic burst instantaneous frequency (fm1) of a first ultrasonic subburst within an ultrasonic burst (UB); sf2 second frequency profile of the second ultrasonic burst instantaneous frequency (fm2) of a second ultrasonic subburst within an ultrasonic burst (UB). Within the ultrasonic burst (UB), this second ultrasonic subburst is typically superimposed on the first ultrasonic subburst, preferably by summation; SF3 is a third frequency profile of the third ultrasonic burst instantaneous frequency (fm3) of a third ultrasonic subburst within an ultrasonic burst (UB). Within the ultrasonic burst (UB), this third ultrasonic subburst is typically superimposed on the first ultrasonic subburst and the second ultrasonic subburst preferably by summation; s1 first distance of the first ultrasonic sensor system (USS1) from the object (O) s2 second distance of the second ultrasonic sensor system (USS2) from the object (O) smt1erste single mode time; smt2zweite single mode time; smt3dritte single mode time; USA ultrasonic system axis; USS ultrasonic sensor system; USS1 first ultrasonic sensor system; USS2 second ultrasonic sensor system; t time; t1 / 50%erster Half-frequency time. At this first half-frequency time (t1 / 50%), the first ultrasound transducer (US1) transmits at a first half-frequency (f1 / 50% ); t1aerste burst time phase; t1bzweite burst time phase; t1serster transmission start time; t1eerster transmission end time; t2 / 50%zweiter half-frequency time. At this second half-frequency time (t2 / 50%), the second ultrasound transducer (US2) transmits at a second half-frequency (f2 / 50% ); t2szweiter transmission start time; t2ezweiter transmission end time; t3 / 50%dritter half-frequency time. At this third half-frequency time (t3,50%), the third ultrasound transducer (US3) transmits at a second half-frequency (f3 / 50% ); t3sdritter transmission start time; t3edritter transmission end time; T0nullte ultrasound period duration of the zeroth ultrasound period of the zeroth ultrasound pulse (P0 ); T1erste ultrasound period duration of the first ultrasound period of the first ultrasound pulse (P1 ); T2zweite ultrasound period duration of the second ultrasound period of the second ultrasound pulse (P2 ); T3dritte ultrasound period duration of the third ultrasound period of the third ultrasound pulse (P3); T4vierte ultrasound period duration of the fourth ultrasound period of the fourth ultrasound pulse (P4); T5fünfte ultrasound period duration of the fifth ultrasound period of the fifth ultrasound pulse (P5); T6sechste ultrasound period duration of the sixth ultrasound period of the sixth ultrasound pulse (P6); T7siebte ultrasound period duration of the seventh ultrasound period of the seventh ultrasound pulse (P7); Tjj-th ultrasound period duration of the j-th ultrasound period of the j-th ultrasound pulse (Pj) (here, j stands for an integer positive number); UB ultrasound burst; UBS ultrasound burst start; UBE ultrasound burst end US1 first ultrasound transducer; US2 second ultrasound transducer; US3 third ultrasound transducer; USS ultrasound sensor system; USS1 first ultrasound sensor system; USS2 second ultrasound sensor system; vfFrequenzveränderungsgeschwindigkeit the ultrasound burst instantaneous frequency (fm) over time (t);

Claims

Method for emitting an ultrasonic burst for use in ultrasonic sensor systems in vehicles, comprising the steps of - Step 1: emitting an ultrasonic burst having an ultrasonic burst duration (bd) which does not exceed a maximum ultrasonic burst duration (bd), by an ultrasonic sensor system (USS); - Step 2: receiving an ultrasonic burst reflected by an object (O); - Step 3: determining the distance (D) between the ultrasonic sensor system (USS) and the object (O) as a function of the received reflected ultrasonic burst; - Step 4: Repeating steps 1 to 4, wherein the ultrasonic burst duration (bd) depends on the determined distance (D, s1, s2), characterized in that - the ultrasonic burst length of the ultrasonic burst duration (bd) is increased with the fourth root of the determined distance (D).Method according to Claim 1 - wherein the amplitude (A) of the transmitted ultrasonic burst depends substantially in proportion to (D+D 0)1 / k, where 2≤k≤5 or preferably k=2 or k=4, on the distance (D) determined, where D 0 is a constant which can be zero.Method according to one or more of Claims 1 to 2, - wherein at least a plurality of ultrasonic bursts (UB) are transmitted at an ultrasonic burst interval in time, and - wherein the first ultrasonic burst interval is the interval between the ultrasonic burst start (UBS) of a first ultrasonic burst and the ultrasonic burst start (UBS) of the second ultrasonic burst immediately following this first ultrasonic burst, and - wherein the second ultrasonic burst interval between the ultrasonic burst start (UBS) of the second ultrasonic burst and the ultrasonic burst start (UBS) of the third ultrasonic burst immediately following this second ultrasonic burst depends on the distance (D) determined.Method according to one or more of Claims 1 to 3, - wherein the temporal ultrasonic burst distance of the ultrasonic bursts becomes shorter in time as the spatial distance (D) between the ultrasonic sensor system and the object (O) decreases.Method according to Claim 4-- wherein the temporal ultrasonic burst distance of the ultrasonic bursts becomes shorter by a length l in the event of a shortening of the spatial distance (D) between the ultrasonic sensor system and object (O) with c as the speed of sound with a tolerance of + / - 25% and / or with a tolerance of + / - 10% and / or with a tolerance of + / - 5%.Method according to one or more of Claims 1 to 5, - wherein the number of ultrasonic burst instantaneous frequencies (f m1, f m2, f m3) and the associated number of frequency profiles (SF1, SF2, SF3) of these ultrasonic burst instantaneous frequencies (f m1, f m2, f m3) within an ultrasonic burst (UB) depends on the distance (D).

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