SPEAKER FOR A MOTOR VEHICLE, VEHICLE DOOR, MOTOR VEHICLE AND METHOD FOR CONTROLLING A SPEAKER

Abstract

The invention relates to a loudspeaker for a motor vehicle, comprising at least the following components: - a membrane for emitting sound waves into the environment; - an electric drive unit to drive the membrane; and - A loudspeaker cover that protects the loudspeaker diaphragm from the surrounding environment. The loudspeaker is characterized primarily by the fact that the loudspeaker cover incorporates at least one piezoelectric element by means of which a change in the shape of the loudspeaker cover can be detected. The piezo element on the speaker cover allows for very precise measurement of the actual value of harmonic distortion, thus enabling precise adjustment of the speaker to various disturbances, for example in a closed control loop.

Description

[0001] The invention relates to a loudspeaker for a motor vehicle, a vehicle door with such a loudspeaker for a motor vehicle, a motor vehicle with such a loudspeaker, and a method for controlling such a loudspeaker.

[0002] Speakers in sound systems, such as those in motor vehicles, are typically exposed to highly variable environmental conditions. For example, speakers in a sound system are often installed in vehicle doors, such as those leading to the passenger compartment and / or the trunk. There, they are always at least indirectly exposed to fresh air and drafts, because vehicle doors are never completely airtight.

[0003] In a loudspeaker installed in a vehicle door, for example at high vehicle speeds, the suction effect of the airflow in the cavities between the outer shell and the inner door panel creates a negative pressure behind the loudspeaker compared to the interior, towards which the desired sound output is directed. This causes the loudspeaker diaphragm to assume a new static resting position because the suction effect deflects the diaphragm from its usual static resting position.

[0004] This shift in the resting position means that the loudspeaker can no longer be driven at its nominal output, i.e., the maximum excursion towards the suction side is reduced, and thus the overall maximum sound pressure level within the maximum excursion for distortion-free reproduction is lowered. This applies analogously to positive pressure at the rear of the loudspeaker. It should be noted here that for sound reproduction, a diaphragm amplitude symmetrical to the resting position is necessary. Therefore, any shift in the resting position leads to a reduction in the maximum sound pressure level for distortion-free reproduction.

[0005] According to known solutions, this disadvantage is addressed by using an open control loop. Here, the maximum possible control voltage is reduced depending on the vehicle speed. However, this occurs without feedback regarding the actual influence of the ambient conditions. For example, the actual ambient conditions might require a higher or lower control voltage than the one currently being applied by the speed-dependent control. Consequently, the user experiences either an unnecessarily reduced maximum sound level or, conversely, distortion and thus a deterioration in sound quality due to overly optimistic control.

[0006] CN 216649979 U describes a loudspeaker module and an electronic device, wherein the loudspeaker module comprises an enclosure, a loudspeaker, and a smart power amplifier. The loudspeaker and the smart power amplifier are housed within the enclosure. The smart power amplifier is connected to the loudspeaker. The smart power amplifier comprises a first detection module and a digital audio processor, which are interconnected. The first detection module is connected to the digital audio processor. The first detection module serves to detect the acoustic properties of a second audio signal, which is played when the loudspeaker emits the first audio signal, and to feed the acoustic properties back to the digital audio processor.

[0007] JP S5990492 A describes a feedback microphone that is placed near the diaphragm of the tweeter and detects a reproduced sound from the tweeter and controls the loudspeaker.

[0008] Based on this, the present invention aims to overcome, at least partially, the disadvantages known from the prior art. The features of the invention are defined in the independent claims, for which advantageous embodiments are shown in the dependent claims. The features of the claims can be combined in any technically meaningful way, whereby the explanations in the following description and features from the figures, which comprise supplementary embodiments of the invention, can also be used.

[0009] The invention relates to a loudspeaker for a motor vehicle, comprising at least the following components: - a membrane for emitting sound waves into the environment; - an electric drive unit to drive the membrane; and - a speaker cover that protects the speaker's diaphragm from the surrounding environment.

[0010] The loudspeaker is characterized primarily by the fact that at least one piezoelectric element is provided in the loudspeaker cover, by means of which a change in the shape of the loudspeaker cover can be detected.

[0011] Unless explicitly stated otherwise, ordinal numbers used in the preceding and following descriptions serve solely for unambiguous differentiation and do not indicate any order or ranking of the components referred to. An ordinal number greater than one does not necessarily imply the presence of another such component.

[0012] The loudspeaker proposed here is suitable for use in a motor vehicle, but can also be used in other environments, such as loudspeakers for other vehicles (e.g., aircraft and watercraft), outdoor applications, and headphones. The loudspeaker is particularly well-suited for use in a vehicle door. However, it goes without saying that the loudspeaker is not limited to such applications. Rather, it is suitable for use in any other application where it is exposed to the environmental conditions described above and below, or to other influences.

[0013] The diaphragm is preferably a loudspeaker diaphragm of a known type. The diaphragm is designed to emit sound waves as a result of air movement induced by its vibration around a rest position. Such a diaphragm is often circular, with a (radially outer) edge fixed around its circumference (preferably spring-loaded via a surround) and its radial center being axially deflectable by the drive unit to produce a vibration (i.e., dependent on the tone to be generated [frequency of the movement between two positions] and sound level [amplitude of the movement]) between two maximum positions. The maximum position is determined, at least in high-quality loudspeakers, by the THD (Total Harmonic Distortion), thus preventing harmonic distortion, ringing, and clipping at excessively high volumes (high sound pressure levels).But these problems occur when the diaphragm's rest position is shifted from its intended position, i.e., when the maximum amplitude for the diaphragm's intended position, as designed, lies beyond the maximum stroke position in this shifted actual position.

[0014] The electric drive unit, for example, includes a voice coil and an electromagnet, which precisely and energy-efficiently drives the diaphragm to produce sound waves, resulting in a clean, wave-like motion with low inertia. Regardless of the drive unit's design, electrical signals are transmitted to the electric drive unit, as is common with loudspeakers. Based on these signals, the electric drive unit activates the electromagnet, which in turn transmits a changing magnetic field to the voice coil connected to the diaphragm. The moving voice coil then transmits these movements to the diaphragm, which in turn generates sound waves.

[0015] Besides magnets and voice coils, there are alternative drive systems for loudspeakers. Electrostatic drivers offer high sound quality and low distortion and are used in high-end hi-fi loudspeakers. Ribbon loudspeakers are characterized by very precise and fast response as well as a wide frequency range and are also used in high-end hi-fi loudspeakers, especially in the tweeters. Planar magnetic drivers offer high fidelity and uniform sound dispersion and are used in high-end hi-fi loudspeakers and headphones.

[0016] In one embodiment, the loudspeaker preferably also includes a centering element for centering the diaphragm and / or a surround. The surround is designed to provide a defined, spring-like connection between the diaphragm and its loudspeaker basket.

[0017] A speaker grille is essentially a conventional textile cover (for example, made of fabric) that primarily serves to provide mechanical protection and prevent dirt from getting into the diaphragm. It should be noted that such a grille is not essential for the proper functioning of a speaker. Speaker grilles are often perforated, allowing air to pass through. However, the grille will always be moved to some extent by the sound waves.

[0018] As described above, the diaphragm is displaced from its resting position due to an environmental condition, such as a change or the creation of a pressure gradient across the diaphragm. In one scenario, temperature influences cause stiffening, thus altering the maximum stroke. Similar effects occur, for example, with aging and / or production fluctuations. It should be noted that in one scenario, a combination of influences may be present, which may overlap and thus either increase or cancel each other out.

[0019] A piezoelectric element is a component that preferably utilizes the piezoelectric or piezoresistive effect to convert mechanical deformations into a (changed) electrical voltage or a (changed) electrical resistance. This property is used here to advantageously employ at least one piezoelectric element as a kind of microphone to detect the sound waves of the adjacent diaphragm. It is proposed here to position at least one piezoelectric element near, in, and / or on the loudspeaker cover. This places the at least one piezoelectric element close to the sound source, i.e., the diaphragm, and thus detects deviations in the loudspeaker's sound output with minimal interference (besides the other external interference considered here and requiring compensation).

[0020] Thus, the current harmonic distortion at the given sound level can be detected using the piezoelectric element arranged in this way. It should be noted that in one embodiment, the displacement of the diaphragm is detected. In another embodiment, the sound quality is determined, i.e., the degree of THD is measured, which results from comparing the input signal from an amplifier or power stage with the current deformation of the diaphragm detected by the piezoelectric element. It should be noted that for most applications, a deviation within a defined limit is permissible for the required sound quality. Only when a defined limit is exceeded is a disturbance detected that requires control intervention to achieve the desired sound quality.

[0021] The measured harmonic distortion closely approximates (due to the small distance and thus minimal lateral influences) the actual sound emanating from the loudspeaker. However, the movement of the diaphragm responsible for emitting sound waves is influenced by at least one environmental condition and therefore does not exactly match the input signal and its intended harmonic distortion. Capturing these sound waves at the position of the loudspeaker cover (using at least one piezoelectric element) thus enables a very precise measurement of the sound waves emitted by the diaphragm. Furthermore, due to its physical properties, the at least one piezoelectric element allows for a highly reliable and precise measurement of the emitted sound waves and, consequently, the sound quality, by accurately detecting the shape changes of the loudspeaker cover.It should be noted that these are minimal changes in shape.

[0022] The comparison of the actual harmonic distortion value, as present in the loudspeaker cover, with the target harmonic distortion value, as specified by the drive unit's control signal, is preferably integrated into a closed-loop control system. The target value can be extracted from the control signal or the audio source (audio file, audio stream). In a simplified example, when outputting a constant tone at a constant volume, an input variable (tone and volume) is entered as a single or separate target variable, or as a (deviation-free) target value. The actual value is measured by at least one piezoelectric element. If a deviation occurs, for example, a plateau in a sine wave input as the target value, a threshold value is exceeded when comparing the actual value with the target value.Based on this comparison, a control variable is then applied to the target value (for example, in the case of separate signal sources, only the volume or amplitude of the input signal), i.e., the maximum permissible volume is adjusted.

[0023] In a further advantageous embodiment of the loudspeaker, it is proposed that at least one of the piezo elements is incorporated into the loudspeaker cover.

[0024] In one embodiment, the piezoelectric element, or at least one of several piezoelectric elements, is glued onto the loudspeaker cover, or alternatively or additionally sewn onto the loudspeaker cover, which is made of textile.

[0025] By directly attaching at least one piezoelectric element to the loudspeaker grille, even better detection of the diaphragm's movements is possible, because the grille preferably moves along with the diaphragm. The movement of the diaphragm, or rather the air, in accordance with the emitted sound wave is transmitted to the loudspeaker grille, which thus vibrates. The at least one piezoelectric element is thereby deformed accordingly, and this deformation results in an electronically detectable change in voltage or resistance, which can be processed as a measured value or directly (i.e., without further processing) fed into a closed control loop as a disturbance variable. Processing involves filtering and / or computer-aided processing, possibly using a so-called look-up table (LUT) with stored values ​​and associated control variables.In one embodiment, a heuristic or machine learning is used alternatively or additionally.

[0026] In an advantageous embodiment of the loudspeaker, it is further proposed that at least one of the piezo elements is designed as a piezo filament.

[0027] It is proposed here that the piezoelectric element, or at least one of several piezoelectric elements, be a piezoelectric filament. This makes integrating such a piezoelectric element into the speaker grille particularly easy and ensures a particularly reliable transmission of the vibration to such a piezoelectric element, i.e., the piezoelectric filament. Furthermore, assembly and integration into the manufacturing process are especially simple because such a piezoelectric element is integrated into an existing component of the speaker. Therefore, hardly any additional space is required, only for the electronic connections. Thus, the additional installation space required for such a speaker is negligible or even nonexistent.

[0028] Another advantage of this embodiment is that at least one piezo element is located very close to the sound source, i.e., directly behind the diaphragm where the sound level originates, and thus the actual value of the harmonic distortion can be measured in a particularly unadulterated manner.

[0029] In an advantageous embodiment of the loudspeaker, it is further proposed that a control unit is included by means of which the maximum drive voltage of the loudspeaker's electrical drive unit is adjusted. Specifically, if a harmonic distortion detected by at least one piezoelectric element is too strong, the maximum control voltage is reduced; and if a harmonic distortion is subsequently acceptable, The maximum control voltage is increased again.

[0030] It should be noted that in one embodiment the control unit is a component of the loudspeaker. Alternatively or additionally, such a control unit, or a component of the control unit, is located in or on an external device, for example an amplifier, a (e.g., digital) power amplifier for the final amplification of the signal, a preamplifier (which amplifies weak signals before they are passed on to the power amplifier), a receiver for radio reception, and / or an equalizer (for adjusting the frequency ranges of an audio signal to optimize the sound).

[0031] The control unit compares the sound waves detected by at least one piezoelectric element, which represent the actual value of the harmonic distortion, with a target value for the harmonic distortion of the input signal. This target value corresponds to the harmonic distortion of the input signal that the loudspeaker, or rather its diaphragm, would produce under optimal environmental conditions, provided the diaphragm's movement is not affected by external disturbances. The precise deviation of the actual value from the target value is determined, and based on this deviation, a necessary drive voltage is calculated. The control unit then uses this voltage to drive the loudspeaker's diaphragm.This compensates for the difference between the actual value and the target value, or shifts the sound level into a permissible (or sound-optimized) excursion range of the loudspeaker, which usually means reducing the maximum volume output.

[0032] Such a control loop has a duration of, for example, between 5 ms [five milliseconds] and 50 ms. This type of adjustable interference therefore does not impair the operation of the loudspeaker to an extent that would be perceived as interference by the average user. The user thus has an undisturbed listening experience.

[0033] The advantage of this design lies in the fact that, firstly, the use of at least one piezoelectric element enables particularly simple and precise measurement of the actual harmonic distortion. Secondly, the drive voltage is individually adjusted to the ambient conditions and their intensity. This avoids a general adjustment of the drive voltage based, for example, on the vehicle's speed. This results in improved sound quality and a higher maximum loudspeaker volume compared to previous technologies.

[0034] For example, if there is a negative pressure on the back of the diaphragm, reducing the drive voltage prevents the user from perceiving distortions in the sound image due to incorrect control of the loudspeaker.

[0035] For example, if the control voltage is simultaneously adjusted based on the vehicle's speed, where inaccurate values ​​or a safety margin is maintained, increasing the control voltage prevents the maximum loudspeaker volume from being unnecessarily reduced due to excessive reduction.

[0036] It should be noted that in a closed control loop, it is possible to dynamically adjust the volume. This means that in the event of a static disturbance (for example, a nearly constant negative pressure at the rear or a reduced temperature), a normal volume level is available, as it would be in an undisturbed state of the loudspeaker. Only when the currently available maximum sound level is reached or exceeded is the drive voltage, and thus the volume, reduced. In the event of a dynamic disturbance (for example, entering a tunnel, driving over a freestanding bridge, or passing a truck), the drive voltage can also be adjusted quickly and directly to maintain optimal sound quality.

[0037] It should be noted that in one embodiment, the method is not used, or not exclusively used, to ensure optimal sound quality, but (if applicable) also to ensure that no overload occurs at the diaphragm and / or the drive. This eliminates the need for other safety measures, or allows them to be implemented with less effort solely to prevent major damage, for example, in the event of a failure of such a control loop.

[0038] According to another aspect, a vehicle door for a motor vehicle is proposed, featuring an outer shell and an inner lining, wherein at least one loudspeaker according to an embodiment as described above is arranged in the inner lining, preferably, at least one of the loudspeakers is oriented with its loudspeaker cover towards the interior of a motor vehicle.

[0039] In one embodiment, a microphone is placed in the B-pillar, headliner, or other locations in a passenger cabin of a motor vehicle to detect THD and implement the control loop proposed here. However, the loudspeaker cover proposed here, with its at least one piezoelectric element, allows for more precise measurement and is also less space-consuming because it eliminates the need for wiring to the at least one remotely located microphone. It should be noted that such a microphone can be used additionally for this or other purposes.

[0040] The outer shell, for example, is a formed sheet metal part, such as aluminum and / or an organosheet, which faces the vehicle's surroundings and is usually visible. The inner panel, on the other hand, faces the vehicle's interior, preferably the passenger compartment or a passenger, and is usually visible from inside the vehicle. A loudspeaker is typically integrated into the inner panel or, alternatively, mounted beneath it, for example, on the outer shell. It should be noted that a vehicle door often has additional components between the outer shell and the inner panel, such as stiffening elements for crash absorption and / or sound-absorbing material, as well as other functional components, such as a locking system, a window lift mechanism, and / or a mounting and drive mechanism for a windshield wiper.

[0041] The membrane is designed to emit sound into the interior, and the speaker cover is (preferably as part of a single-unit speaker) integrated into the interior trim or represents (at least visually) a (visually uniform or separate) part of the interior trim.

[0042] It should be noted that the loudspeaker proposed here can also be used for sound output to the surroundings of the vehicle, i.e., with an outward-facing diaphragm and outward-facing speaker grille, as is currently common practice in police vehicles, ambulances, and fire engines. In these cases, the requirements for THD (Total Dispersion) are often lower, but speech transmission in particular demands a high level of sound quality.

[0043] It should be noted again that the speaker grille is generally not necessarily an aesthetically pleasing component, but rather serves, for example, solely to protect against dirt and debris. This applies to sound output to the surrounding environment as well as to the interior, particularly for a subwoofer or concealed tweeters and / or speakers of a so-called surround sound system. At the same time, it should be pointed out that the piezoelectric element can be integrated very discreetly into a speaker grille without compromising its aesthetic appeal.

[0044] According to a further aspect, a motor vehicle is proposed comprising a drive train, a chassis, at least one vehicle door, preferably according to an embodiment as described above, and an interior, wherein at least one loudspeaker is provided according to an embodiment as described above. preferably at least one of the loudspeakers with its The speaker cover is oriented towards the interior of the vehicle.

[0045] The motor vehicle is, for example, a passenger car or a commercial vehicle. The powertrain, together with the chassis, is designed for the (preferably comfortable) transport of people and / or goods located in the vehicle's interior, through which at least one vehicle door provides external access. With at least one door closed, the interior is adequately protected from the wind, although the connection to the surrounding air is usually somewhat delayed or even completely sealed. This can lead to a change in pressure gradient across the diaphragm of at least one loudspeaker under certain operating conditions. Furthermore, a loudspeaker is often exposed to significant temperature fluctuations, for example, in a parked (out-of-service) vehicle that is neither cooled nor heated.At the same time, loudspeakers are usually put into full use without further delay as soon as the motor vehicle is put into operation.

[0046] According to another aspect, a method for controlling a loudspeaker is proposed according to an embodiment as described above, wherein the method includes at least the following steps of a control loop: a. by means of at least one piezoelectric element, detection of a change in the shape of the loudspeaker cover, whereby a harmonic distortion can be derived from the detected changed shape of the loudspeaker cover; b. by means of a control unit, comparing the harmonic distortion detected in step a. with a current input signal from the loudspeaker; and c. by means of a control unit, adjusting a control voltage of the electrical drive unit of the loudspeaker depending on the comparison result of step b..

[0047] The advantages and preferred designs listed with regard to the loudspeaker can be transferred analogously, at least optionally, to the process, and conversely, the descriptions listed here for the loudspeaker can be transferred here.

[0048] In step a., the sound waves emitted in the immediate vicinity of the loudspeaker diaphragm are detected by means of at least one piezoelectric element, similar to a microphone. In one embodiment, only a change in the resting position (for example, due to a change in pressure gradient) is detected, or the actual sound output or its harmonic distortion (actual value) is continuously recorded.

[0049] In step b, the control unit compares the actual value of the harmonic distortion recorded in step a with the desired harmonic distortion, or the quality of the original signal-accurate output or input signal (for example, as output by a power amplifier), the predetermined target value of the harmonic distortion. This results in a comparison, whereby a deviation within a limit is often permissible. However, if the limit is exceeded, then (in one embodiment only then) step c follows.

[0050] In step c., the drive voltage is adjusted, for example, reduced, if a sound level causes the diaphragm to move outside the permissible range or beyond the maximum range required for a desired sound quality (e.g., THD). It should be noted that this measurement and the control system based on it are preferably implemented dynamically, as a loop with an intrinsic delay of a maximum of 50 ms [fifty milliseconds] down to a maximum of only 5 ms. Preferably, the system reacts to a dynamic disturbance. In one embodiment, the drive voltage is also (preferably) dynamically adjusted, meaning it is only adjusted if the detected disturbance would lead to an undesirably large or undesirably (or unnecessarily) small movement of the diaphragm.

[0051] It should be noted that in one embodiment, the control unit performing step b is the same as the control unit performing step c. However, this is not mandatory. For example, a comparison is performed in one control unit directly at the loudspeaker, and step c is performed in a control unit in or at the power amplifier. Preferably, both control units (for example, as a single component) are an integral part of the respective loudspeaker, so that no additional wiring is required when installing the loudspeaker. Furthermore, it should be noted that in one embodiment, the control unit is a separate component, for example, a microcontroller. Alternatively, the control unit is integrated as a physical circuit or (preferably) software into another (preferably conventionally designed) component of the sound system.

[0052] In a further advantageous embodiment of the method, it is proposed that the resting position of the membrane is influenced by at least one of the following environmental conditions: - Change in air pressure; - Wind conditions in the immediate vicinity of the loudspeaker; - Change in temperature; - Signs of aging of the loudspeaker; and - Production variations of the loudspeaker.

[0053] It should be noted that the aforementioned environmental conditions are not an exhaustive list. Furthermore, these environmental conditions can also be compensated for in a loudspeaker with a speaker cover and integrated piezoelectric element, even without the use of a control loop, for example in an open control system.

[0054] If the air pressure in the vicinity of the loudspeaker changes, for example, if an overpressure or underpressure builds up on the back of the diaphragm compared to the sound output side, this can cause the diaphragm to shift from its (intended) resting position (as explained earlier). Standard drive is then no longer possible for sufficient sound quality. It is therefore necessary to reduce the maximum drive voltage. In one embodiment, only this maximum value is limited. Alternatively or additionally, for a more uniform sound, other (lower) drive voltages are also reduced (for example, proportionally).

[0055] Under certain wind conditions (for example, with significant wind shear acting on the vehicle), sudden changes in pressure gradients can occur across a loudspeaker diaphragm, which are not significantly dependent on the vehicle speed. However, the same events related to air pressure occur in these situations, and the adjustments can be applied accordingly.

[0056] Changes in the air pressure surrounding the loudspeaker and / or its operating temperature can lead to varying degrees of expansion of the loudspeaker's materials. This can also result in the previously mentioned displacement of the diaphragm from its rest position or a reduced maximum excursion. The appropriate measure can be applied analogously in each case.

[0057] One example of a sign of aging is material wear in a loudspeaker component, such as the material of the (highly stressed) diaphragm and / or a centering element that, due to wear, no longer provides full centering for the diaphragm. Similar principles apply here as explained above regarding the effect of temperature, so the measures described there are applicable here as well.

[0058] Production variations are caused, for example, by material variations, manufacturing tolerances, or assembly tolerances. For instance, the diaphragm may not be positioned precisely in its intended resting position, and therefore the loudspeaker will not operate according to the required maximum harmonic distortion value. Alternatively or additionally, a diaphragm may exhibit a significant deviation in its elasticity, such that even the maximum excursion specified in the design results in a distorted output, or conversely, the diaphragm may be more efficient than specified in the design, yet still exhibit a good actual harmonic distortion value despite external disturbances.

[0059] It should be noted that these influences, and potentially other influences, can accumulate or balance each other. The cause of the detected disturbance is irrelevant for the adjustment or control loop proposed here.

[0060] By adjusting the control voltage using the control unit based on the actual value detected by the at least one piezo element, a very precise adaptation of the loudspeaker to different environmental conditions is possible.

[0061] The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way limited by the purely schematic drawings, although it should be noted that the drawings are not dimensionally accurate and are not suitable for defining size relationships. It is illustrated in Fig. 1: a schematic sectional view of a loudspeaker integrated into a vehicle door; Fig. 2: in a schematic sectional view of the integrated loudspeaker according to Fig. 1; Fig. 3: in a schematic sectional view, a loudspeaker with loudspeaker cover; Fig. 4: in a schematic block diagram, the sequence of a procedure for controlling a loudspeaker as a control loop; and Fig. 5: A motor vehicle with a sound system in a partially transparent spatial view.

[0062] In Fig. Figure 1 shows a schematic sectional view of a loudspeaker 1 integrated into a vehicle door 11. The vehicle door 11 has an outer shell 12 facing the environment 5 and an inner panel 13 facing the interior 14, with a cavity 25 formed between them. The loudspeaker 1 has a diaphragm 3 which, as shown, oscillates left and right around a rest position to emit sound waves 4. The loudspeaker 1 is integrated into the inner panel 13, for example, when used in a motor vehicle 2 facing an interior 14. The construction and function of the loudspeaker 1 with loudspeaker cover 7 are illustrated in [reference missing]. Fig. 3 explained.

[0063] For example, when a static voltage is applied (e.g., ±9 V [plus / minus nine volts]), the diaphragm 3 is deflected from its rest position (e.g., by ±5 mm [plus / minus five millimeters]). If the drive voltage 10 is greater than the maximum permissible voltage, the resulting deflection, which may exceed the maximum permissible stroke, can lead to distortion in the sound quality. A schematic representation of such a stroke 22 between two maximum stroke positions (negative stroke position 23 and positive stroke position 24) is shown here.

[0064] In Fig. Figure 2 shows a schematic sectional view of the integrated loudspeaker 1 according to Fig. Figure 1 shows that the diaphragm 3 is displaced from its design (normal) rest position 20 into a deflected rest position 21, for example, due to a rearward negative pressure (in the cavity 25 of the vehicle door 11) caused by the airflow. The normal rest position 20 according to Fig. Number 1 is indicated here with a dashed line for comparison.

[0065] The maximum stroke positions of 23, 24 are the same here as in Fig. 1 shown unchanged. However, if the stroke movement 22 also changes due to an unchanged control voltage 10 (compare Fig. 4) If the position is identical from the deflected rest position 21, the diaphragm 3 is moved beyond the negative stroke position 23. This usually leads to an impairment of the sound quality.

[0066] In Fig. Figure 3 shows a schematic sectional view of a loudspeaker 1 with loudspeaker cover 7.

[0067] The loudspeaker 1 shown here as an example is a diaphragm loudspeaker and, for the sake of clarity and without excluding general application, features conventional components, which are briefly explained below. A (sound wave-emitting) diaphragm 3 is moved up and down by an electric drive unit 6, as shown, to produce a clean, constant tone in a sinusoidal oscillation. The drive unit 6 optionally includes a voice coil 30, which is moved up and down by an electromagnet (with two opposing pole plates 27 and a (permanent) magnet 26 acting as a moving coil).

[0068] Furthermore, the membrane 3 is centrally held by a centering element 28 (for example, the so-called spider) and (here purely optionally via a surround 31) is connected at its outer edge to a loudspeaker basket 32 ​​in a spring-like manner.

[0069] Furthermore, the loudspeaker 1 has a loudspeaker cover 7, which is connected here (purely optionally) to the loudspeaker basket 32, or alternatively to an adjacent component, for example an interior trim panel 13 of a vehicle door 11.

[0070] The loudspeaker cover 7 comprises one or more piezoelectric elements 8, which are indicated here by a dashed line in the center of the loudspeaker cover 7. It is understood, however, that the piezoelectric element 8 can also be arranged at a different location on the loudspeaker cover 7 and / or, for example, be designed as a piezoelectric thread woven into a textile, or be provided multiple times or be formed from a plurality of individual piezoelectric elements 8, preferably as subcomponents of a sensor array.

[0071] The at least one piezoelectric element 8 is designed such that it detects sound waves 4 emitted by the diaphragm 3 and passing through the loudspeaker cover 7, or causing the loudspeaker cover 7 to vibrate. If these sound waves 4 are influenced by at least one environmental condition, the movement of the loudspeaker cover 7 is also changed, and this deviation is detected by the at least one piezoelectric element 8. The movement of the loudspeaker cover 7 represents an actual value 17 of a harmonic distortion with extremely low (further) cross-influence.

[0072] In Fig. Figure 4 shows a schematic block diagram illustrating the process for controlling a loudspeaker 1 as a control loop. The process is shown, without exclusion of generality, purely for the sake of clarity, using the diagram in Figure 4. Fig. 3 loudspeakers shown are explained below.

[0073] In step a. of the procedure, a change in shape of the loudspeaker cover 7 is detected, which, without or with negligible further lateral influences, detects the harmonic distortion originating from the diaphragm 3 of the loudspeaker 1, and can therefore be used as the actual value 17 of the harmonic distortion of the sound waves 4 emitted by the loudspeaker 1.

[0074] In step b., the previously recorded harmonic distortion is compared with a current input value 18 of the sound level, as generated by a control unit 9. As a result of this comparison, the comparison result 19, influenced by at least one environmental condition, i.e., any deviation beyond a limit of the diaphragm 3 of the loudspeaker 1 from the nominal rest position, is determined.

[0075] In step c., based on the comparison result 19, the necessary adjustment of the drive voltage 10 for driving the loudspeaker 1 is made (for example, reducing the amplitude, and thus making it quieter) in order to compensate for the actual deflection of the diaphragm 3 which leads to a reduction in sound quality.

[0076] After being driven with the adjusted control voltage 10, the actual deflection, i.e., the actual value 17, is measured again. This creates a closed control loop, which significantly improves the sound quality of the loudspeaker 1 compared to known methods under changing environmental conditions.

[0077] The steps are performed within a control unit 9, which is, for example, part of the loudspeaker 1 and / or part of, for example, a power amplifier 34.

[0078] In Fig. Figure 5 shows a motor vehicle 2 with a sound system comprising a plurality of loudspeakers 1, which are configured to output sound to the interior 14. It should be noted that identical components are referred to only once here pars pro toto. These loudspeakers 1 are controlled by a common power amplifier 34. In one embodiment, the power amplifier 34 comprises a single common control unit 9 for executing the method for controlling a loudspeaker 1 (preferably as a control loop, for example as with reference to Fig. 4 described). Alternatively or additionally, one, several or all of the loudspeakers 1 have their own, preferably structurally integrated, control unit 9 for carrying out this method.

[0079] In the embodiment shown, the sound system comprises the following loudspeakers 1: - a central speaker 35 at the front of the cockpit, - two midrange drivers 36 and woofers 37 in the side vehicle doors 11 near the front seats, - two rear speakers 38 in the side vehicle doors 11 near the rear seat, - two surround speakers 39 left and right behind the rear seat, for example integrated into the rear vehicle door 11 (so-called trunk lid), and - a subwoofer 40 in the trunk 29 or below the loading area of ​​the trunk 29.

[0080] The motor vehicle 2 also features a drive train 15 and a chassis 16 for the comfortable transport of persons and / or goods, here designed as a passenger car primarily for passengers. The sound system shown here is primarily designed for sound output to the passenger cabin 33 of the motor vehicle 2 with the highest possible sound quality.

[0081] The piezo element on the speaker cover allows for very precise measurement of the actual value of harmonic distortion, thus enabling precise adjustment of the speaker to various disturbances, for example in a closed control loop. Reference symbol list 1 speaker 2 motor vehicles 3 Membran 4 sound waves 5 Environment 6 Drive unit 7 Speaker cover 8 Piezoelectric element 9 Control unit 10 Control voltage 11 Vehicle door 12 Outer shell 13 Interior trim 14 Interior 15 Powertrain 16 Chassis 17 Actual value 18 Input size 19 Comparison result 20 normal resting position 21 deflected rest position 22 Lifting movement 23 negative stroke position 24 positive stroke position 25 cavity 26 Magnet 27 pole plate 28 Centering element 29 trunk 30 Voice coil 31 groove 32 speaker basket 33 passenger cabin 34 Power stage 35 central loudspeakers 36 midrange drivers 37 woofers 38 rear speakers 39 surround speakers 40 subwoofers

Claims

[1] Loudspeaker (1) for a motor vehicle (2), comprising at least the following components: - a membrane (3) for emitting sound waves (4) into the environment (5); - an electric drive unit (6) for driving the membrane (3); and - a loudspeaker cover (7) which covers the diaphragm (3) of the loudspeaker (1) towards the environment (5), characterized by , that at least one piezo element (8) is provided in the loudspeaker cover (7) by means of which a change in shape of the loudspeaker cover (7) can be detected. [2] Loudspeaker (1) according to claim 1, wherein at least one of the piezo elements (8) is incorporated into the loudspeaker cover (7). [3] Loudspeaker (1) according to claim 1 or claim 2, wherein at least one of the piezo elements (8) is designed as a piezo filament. [4] Loudspeaker (1) according to one of the preceding claims, further comprising a control unit (9) by means of which the maximum drive voltage (10) of the electrical drive unit (6) of the loudspeaker (1) is adjusted, namely if a harmonic distortion detected by at least one piezoelectric element (8) is too strong, the maximum control voltage (10) is reduced; and If harmonic distortion is subsequently acceptable, the maximum drive voltage (10) is increased again. [5] Vehicle door (11) for a motor vehicle (2), comprising an outer shell (12) and an inner lining (13), wherein at least one loudspeaker (1) according to one of the preceding claims is arranged in the inner lining (13). [6] motor vehicle (2), comprising a drivetrain (15), a chassis (16), at least one vehicle door (11) and an interior (14), wherein at least one loudspeaker (1) is provided according to any one of claims 1 to 4. [7] Method for controlling a loudspeaker (1) according to any one of claims 1 to 4, wherein the method comprises at least the following steps of a control loop: a. by means of at least one piezo element (8), detecting a change in shape of the loudspeaker cover (7), wherein a harmonic distortion can be derived from the detected changed shape of the loudspeaker cover (7); b. by means of a control unit (9), comparing the harmonic distortion detected in step a. with a current input signal (18) of the loudspeaker (1); and c. by means of a control unit (9), adjusting a control voltage (10) of the electrical drive unit (6) of the loudspeaker (1) depending on the comparison result (19) of step b.. [8] Method according to claim 7, wherein the rest position of the membrane is influenced by at least one of the following environmental conditions: - Change in air pressure; - Wind conditions in the immediate vicinity of the loudspeaker (1); - Change in temperature; - Signs of aging of the loudspeaker (1); and - Production variations of the loudspeaker (1).

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