Acoustic sensor housing for detecting airborne sound in the exterior of vehicles moving in air fluid and vehicle comprising one or more such acoustic sensor housings

Abstract

Acoustic sensor housing (10) for detecting airborne sound in the exterior of vehicles moving in an air fluid, the acoustic sensor housing (10) comprising a housing cover (1) comprising an opening (2) for air inlet that is symmetrical to an axial axis (A) of the acoustic sensor housing (10), a spherical body (3) arranged axially symmetrically in the opening (2), an inflow component (4) arranged behind the spherical body (3) in the air flow direction and comprising a sound channel (5) in the form of a continuous hollow space parallel to the axial axis (A), wherein the spherical body (3) is fixed to the inflow component (4) on an outflow side (6) by means of an acoustically permeable membrane (7) that protects the sound channel (5) against the action of foreign bodies, and wherein a flow bypass (8) that directs foreign bodies that have entered the acoustic sensor housing (10) through the air flow away from the membrane (7) and out of the acoustic sensor housing (10) leads out,by a free space between the surface of the spherical body (3), the membrane (7), the inflow component (4) and an inner wall (9) of the housing cover (1).

Description

[0001] The invention relates to an acoustic sensor housing for detecting airborne sound in the exterior of vehicles moving in an air fluid. Furthermore, the invention relates to a vehicle comprising one or more such acoustic sensor housings.

[0002] The following definitions, descriptions and statements retain their respective meaning for and apply to the entire disclosed subject matter of the invention.

[0003] Acoustic sensors for detecting external noises outside vehicles, such as emergency vehicle sirens, are known from the prior art. For example, DE 10 2019 206 331 B4 discloses a device for detecting airborne sound for automotive applications.

[0004] Further prior art is shown in DE 10 2019 206 329 A1 and DE 10 2019 210 930 A1.

[0005] An acoustic sensor is a sensor that detects mechanical vibrations, for example caused by airborne sound waves, and converts them into a processable signal, for example, an electrical signal such as an electrical voltage. The acoustic sensor includes an analog and / or digital signal output. The conversion takes place in two stages. In a first acoustic-mechanical conversion stage, the airborne sound is converted into the movement of an object, for example, a membrane of the acoustic sensor, according to a specific reception principle. In the second mechanical-electrical conversion stage, the movement of the object is converted into the electrical signal according to a specific transducer principle. Examples of acoustic sensors include an arrangement of a magnet and an electrical coil, microphones, accelerometers, piezo sensors, or strain gauges.A micro-electro-mechanical system, abbreviated MEMS, comprising an array of semiconductor elements that absorb vibrations, can also be used as an acoustic sensor.

[0006] The microphone can comprise a microphone capsule and a transducer. The acoustic-mechanical conversion takes place in the microphone capsule. The microphone capsule, for example, comprises a diaphragm that is excited to vibrate by airborne sound. The mechanical-electrical conversion takes place in the transducer. The transducer can be, for example, an electrodynamic transducer, such as in a moving coil microphone, or an electrostatic transducer, such as in a condenser microphone. The microphone is, for example, a MEMS microphone. MEMS microphones are miniaturized microphones that are designed, for example, using surface-mounted device (SMD) technology for direct installation on a circuit board. MEMS microphones are small and easy to process industrially; for example, MEMS microphones can be assembled using a reflow soldering process.Compared to other microphones, MEMS microphones are less sensitive to high temperatures, making them particularly well-suited for automotive applications. Alternatively, the acoustic sensor is an electret condenser microphone.

[0007] When a vehicle moves, for example, a wind gust creates turbulent airflow at a vehicle acoustic sensor located on the vehicle's outer skin. The problem is that this turbulence causes noise interference at the acoustic sensor.

[0008] The invention was based on the task of how to achieve the most laminar air flow possible in an acoustic sensor for automotive applications.

[0009] The subject matter of the independent and the subordinate claim each solves this problem by means of a spherical body which generates a laminar flow at an opening of the acoustic sensor.

[0010] Advantageous embodiments of the invention emerge from the definitions, the subclaims, the drawings and the description of preferred embodiments.

[0011] In one aspect, the invention provides an acoustic sensor housing for detecting airborne sound in the exterior of vehicles moving in air fluid.

[0012] The acoustic sensor housing comprises a housing cover. The housing cover can be a molded part, for example, an injection-molded part. The housing cover comprises an opening for air intake that is symmetrical to an axial axis of the acoustic sensor housing. Compared to the subject matter disclosed in DE 10 2019 206 331 B4, the acoustic sensor housing disclosed here has the relatively large symmetrical opening instead of a protective grille. Due to the larger opening, the directivity of the acoustic sensor housing disclosed here is improved. Furthermore, the housing cover comprises a spherical body arranged axially symmetrically in the opening. According to one aspect, the spherical body is arranged centered in the opening. The spherical body can be made of the same material as the housing cover.

[0013] The housing cover also includes an airflow component arranged behind the spherical body in the direction of airflow. According to a further aspect, an upstream side of the airflow component has the shape of a nose cone. The nose cone serves to reduce wind noise in the axially directed airflow and to reduce the dependence of the transmission factor on the angle of incidence of sound at given frequencies.

[0014] The inflow component comprises a sound channel in the form of a hollow space running parallel to the axial axis. The sound channel serves to guide the airborne sound waves towards an acoustic sensor. The sound channel is acoustically specifically dimensioned so that, if possible, no or only a few and weak eigenmodes develop in the usable frequency range of the acoustic sensor. This targeted dimensioning is essentially based on geometric parameters such as diameter, length, volume, and shape. According to a further aspect, the sound channel essentially has the shape of a cylinder, a truncated cone, or a horn section. A horn section, also called a funnel, as in Fig. The system disclosed in section 1 of DE 38 43 033 C2 is a robust system for the highly sensitive detection of airborne sound waves. A sound channel in the form of a horn element acoustically couples the receiver particularly well to the sound field, allowing as much of the externally incoming sound energy as possible to reach the receiver. This achieves minimal acoustic attenuation of the sound energy flow.

[0015] The spherical body is fixed to the inflow component on an outflow side by means of an acoustically permeable membrane, which protects the sound channel from the effects of foreign bodies. The membrane is, for example, a flexible, compressible, silicone membrane, for example a 0.2 mm thick silicone membrane. The membrane seals the sound channel. The flexible nature of the membrane allows the air enclosed in the sound channel to vibrate, which improves wave transmission to the microphone compared to a more rigid membrane, for example one made of plastic. The thin-walled and flexible membrane is capable, in this case, of absorbing and transmitting an acoustic vibration. According to one aspect, the membrane comprises a membrane lip. The membrane lip can rest on the inflow component. The membrane lip can comprise a sealing ring arranged in a groove of the inflow component.

[0016] A flow bypass is created by creating a free space between the surface of the spherical body, the diaphragm, the inflow component, and an inner wall of the housing cover. The flow bypass directs foreign matter that has entered the acoustic sensor housing through the air flow, away from the diaphragm, and out of the acoustic sensor housing. The flow bypass ensures that fluids that have entered through the air inlet, such as water, air, and small particles such as dirt and / or dust, are transported back out of the acoustic sensor at the outlet of the flow bypass. In this sense, the flow bypass is a self-cleaning flow bypass. According to one aspect, an outlet opening of the flow bypass is arranged in a direction different from the direction of sound entry.The flow bypass is acoustically, fluidically, and fluidically designed to reduce the aeroacoustic noise generated by the flow and prevent the fluid dynamic forces from negatively affecting the acoustic sensor, for example, damaging or degrading it. Another aspect is that the flow bypass is symmetrical to the axial axis, thus promoting laminar flow.

[0017] The acoustic sensor housing disclosed here is characterized by the fact that the individual components, such as the opening for the airborne sound inlet, the flow bypass, and the sound channel, are coordinated with each other, taking into account airborne sound, aeroacoustics, flow and fluid dynamics, electronics, and mechanics. The spherical body ensures that essentially laminar flow is established in the acoustic sensor housing.

[0018] Tests by the inventor have also shown that, compared to a prior art acoustic sensor housing without a spherical body, the acoustic sensor housing disclosed here with a spherical body can achieve noise suppression of up to 15 dB for frequencies below 4.5 kHz. For frequencies above 4.5 kHz, a better signal quality is achieved compared to the prior art, with a noise suppression of 30 dB, although some noise patterns, for example, at 9 kHz, are not present. For frequencies below 4 kHz, a noise suppression of 10 dB is achieved. Furthermore, high selectivity, purity, clarity, and higher levels for signal tones from emergency vehicles are achieved.Furthermore, it has been experimentally demonstrated that the broadband noise for frequencies between 20 Hz and 1.3 kHz in the acoustic sensor housing disclosed here has a lower sound pressure level and a sharper limitation at 1.2 kHz compared to the acoustic sensor housing known from the prior art. In particular, the noise in the acoustic sensor housing disclosed here is comparatively evenly distributed over time, thus deterministic, in contrast to the high and non-deterministic peaks in the acoustic sensor housing known from the prior art.

[0019] According to a further aspect, the spherical body is fixed to the inflow component by means of a retaining web. The retaining web serves to reinforce the membrane when compressed by air, particularly in the case of a thin-walled membrane. The retaining web is, for example, a silicone retaining web, for example, a 0.5 mm thick silicone retaining web. The retaining web is, for example, perforated. The perforation improves sound transmission.

[0020] According to another aspect, the retaining web is secured to the inflow component by means of a radial shaft seal clamping device, also known as a Simmerring. The terms clamping device and pressing device are used synonymously.

[0021] For example, the clamping device comprises a tension spring washer. According to one aspect, the clamping device is a radial shaft seal, also called a Simmerring.

[0022] According to a further aspect, the retaining web and the clamping device are designed as a monolithic part.

[0023] According to another aspect, the retaining bar has perforations.

[0024] According to another aspect, the surface of the spherical body includes trough-shaped indentations, similar to the dimples of a golf ball. These indentations reduce the drag coefficient and thus minimize turbulent flows.

[0025] According to a further aspect, the acoustic sensor housing comprises a housing base onto which the housing cover can be placed. The housing base comprises an acoustic sensor, for example a MEMS microphone, which is operatively connected to the sound channel when the housing cover is in place. The housing cover and housing base are preferably fastened to one another by at least one, preferably several, for example three, fastening points coaxial with the axis of rotation via a force-locking and / or form-locking connection. A snap or click closure can be provided for this purpose, for example. This also ensures simple fastening during the manufacturing process or during assembly of the acoustic sensor, which can also be detachable to enable replacement of individual components of the acoustic sensor.The proposed method of fastening the housing cover and housing base also ensures easy access, for example, for replacing or inspecting the membrane. According to one aspect, the acoustic sensor housing includes magnets, for example, cylindrical magnetic pins, by means of which the housing cover can be placed on the housing base.

[0026] According to a further aspect, the housing base comprises a printed circuit board. The printed circuit board comprises, for example, components and their connections for preprocessing analog or digital signals from the acoustic sensor. The components are designed for analog or digital signal processing and / or for implementing filter functions, phase reversal functions, compressor functions, and / or amplifier functions. The components of the printed circuit board comprise, for example, logic components such as ASICS or FPGAs. For example, one component implements a high-pass filter that allows airborne sound waves with frequencies greater than 300 Hz to pass through. The dynamic range of a signal is limited using compressor functions. The components are mounted, for example, directly on the surface of the printed circuit board, for example, soldered, and are also called surface-mounted devices, abbreviated to SMD.

[0027] According to a further aspect, the acoustic sensor housing comprises a heating device that dehumidifies and / or defrosts the acoustic sensor housing. The heating device is, for example, a heating resistor, for example in the form of a heating coil. The heating coil is, for example, integrated into the housing cover.

[0028] According to a further embodiment, the heating device can be designed as a heat cushion. The heat cushion can also be referred to as a heat pad or heating pad. This can be a heat cushion such as those commonly used for heating exterior mirrors or vehicle seats. Advantageously, such a heat cushion can be manufactured cost-effectively.

[0029] According to a further embodiment, the heating element can be free of a thermal insulation layer. This allows, for example, an electrically actively controllable element of the heating element to be directly exposed to the air, for example without additional protection. For use outside of an acoustic sensor, heating pads can be provided with thermal insulation, for example, a rubber. In the present embodiment, however, a heating pad can be provided that is not thermally insulated on the side facing away from the adhesive surface in order to advantageously dissipate as much heat as possible to the area to be dehumidified and / or defrosted.

[0030] The power supply, for example, is integrated into the housing base. According to another aspect, the airflow component is in thermal contact with heat sources. For example, one side of the housing base is designed as a heat source. For example, the airflow component is made of metal for good heat transfer.

[0031] In the direction of airflow or sound waves acting on the acoustic sensor housing, the individual components of the acoustic sensor housing are arranged sequentially as follows, with the housing cover placed on the housing base: Air flowing into the acoustic sensor housing through the opening in the housing cover flows onto the spherical body and past it through the flow bypass. The diaphragm is excited to vibrate by the air flowing past it and by sound waves. The vibrations are transmitted to the sound channel of the inflow component. Sound is transmitted through the sound channel to the microphone.

[0032] According to a further aspect, the invention provides a vehicle. The vehicle comprises one or more of the acoustic sensor housings disclosed herein. The acoustic sensor housings are arranged on an outer skin of the vehicle, for example, integrated into shock absorbers. The vehicle is, for example, an automated vehicle, such as an autonomous shuttle for transporting people or goods.

[0033] According to a further aspect, the vehicle comprises a driving system for automated driving functions. Acoustic sensors housed in the acoustic sensor housings perceive the vehicle's surroundings. The driving system processes data from the acoustic sensors for trajectory planning and / or trajectory control.

[0034] The invention is explained by way of example in the following figures. They show: Fig. 1 a sectional view of an embodiment of an acoustic sensor housing according to the invention, Fig. 2 a detailed view of the membrane of the acoustic sensor housing Fig. 1, Fig. 3 an embodiment of an acoustic sensor housing known from the prior art, hereinafter referred to as type 1, Fig. 4 an embodiment of an acoustic sensor housing according to the invention, hereinafter referred to as type 2, Fig. 5 an embodiment of a membrane of the acoustic sensor housing according to the invention, Fig. 6 shows a further embodiment of a membrane of the acoustic sensor housing according to the invention, Fig. 7 Experimental setup, Fig. 8 Frequency response determination with fan switched on using frequency generator for type 1, Fig. 9 Frequency response determination with fan switched on using frequency generator for type 2, Fig. 10 Frequency response with fan and siren switched on for type 1, Fig. 11 Frequency response with fan and siren switched on for type 2, Fig. 12 Frequency response when driving at v=50km / h for type 1 and Fig. 13 Frequency response when driving at v=50km / h for type 2.

[0035] In the figures, identical reference numerals designate identical or functionally similar parts. For clarity, only the reference parts relevant to the respective understanding are marked in the individual figures.

[0036] The Fig. 1 acoustic sensor housing 10 shown as a sectional view comprises a housing cover 1 and a housing base 20. Air flows through an opening 2 of the housing cover 1 in the air flow direction S, see also Fig. 2, past a spherical body 3 into the acoustic sensor housing 10. Behind an outflow side 6, a substantially laminar flow develops. The spherical body 3 thus reduces turbulence in the acoustic sensor housing. This achieves noise suppression at an acoustic sensor 21. Due to the relatively large opening 2, a relatively large opening angle W for sound waves is achieved, see Fig. 2. A free space between an inflow component 4 and an inner wall 9 of the housing cover 1 forms a self-cleaning flow bypass 8. The inflow component 4 comprises a sound channel 5 in the form of a cavity, extending symmetrically to an axial axis A of the acoustic sensor housing 10. The sound channel 5 conducts the sound to the acoustic sensor 21. The housing base 20 comprises a circuit board 5.

[0037] The spherical body 3 is fixed to the inflow component 4 by means of a membrane 7 and a rotationally symmetrical retaining web H, as Fig. 2 in detail. The membrane 7 rests on the inflow component 4 with a membrane lip M and seals the sound channel 5. For example, the membrane 7 is arranged on the inflow component 4 by means of a sealing ring D. The sealing ring D is arranged, for example, in a groove of the inflow component 4. The retaining web H is fixed to the inflow component 4 by means of a radial shaft sealing ring R, for example.

[0038] Fig. 3 shows a part of the acoustic sensor housing according to type B1 known from the prior art. Fig. 4 shows an acoustic sensor housing 10 with spherical body 3 disclosed here.

[0039] Fig. 5 shows the membrane 7 with retaining bar H in an open version. In Fig. 6 the membrane 7 is folded over, here without a shaft seal.

[0040] Fig. Figure 7 shows the experimental setup used to Fig. 8 to 11 were obtained. The test setup comprises a fan T. The fan T can comprise a vibration absorption plate and an air duct. The fan T generates air flows that simulate air flows that prevail when a vehicle on which the acoustic sensor housing 10 is arranged is traveling. The types B1 and B2 are arranged at an outlet of the fan T, and the sound pressure level is measured with the acoustic sensor 21. The data from the acoustic sensor 21 is evaluated using a data processing device 30, for example, a computer. The data processing device 30 is spaced, for example, 0.7 m from the acoustic sensor housing 10 in order to minimize noise caused by the data processing device, such as the high-frequency whistling of the coils of the power electronics of the data processing device (personal computer), which is barely perceptible or not perceptible to humans.The test setup further includes a sound source Q. The sound source Q is located, for example, 1 m away from the acoustic sensor housing 10. The sound source Q is, for example, a loudspeaker. Using a frequency generator, frequencies ranging from 20 Hz to 12 kHz are scanned and fed into the acoustic sensor housing 10 via the sound source Q. The measuring device for determining the wind speed or volume flow can be a simple anemometer, which can be positioned between the air duct outlet and B1, B2.

[0041] Fig. Figures 8 to 13 show comparative acoustic tests conducted with Type 1 and Type 2 and demonstrate the advantages of Type 2, i.e., the acoustic sensor housing 10 disclosed here. The abscissa represents time in seconds. The ordinate indicates frequencies in Hertz. The color or drawing coding indicates the sound pressure level in decibels. The advantages of Type 2 surprisingly result from the arrangement of the spherical body 3 in the opening 2 of the housing cover 1 of the acoustic sensor housing 10. The spherical body 3 promotes laminar flow and thus contributes to noise suppression.

[0042] Fig. 8, Fig. 9 show frequency responses with fan T switched on with frequency generator; Fig. 8 for type B1 and Fig. 9 for type B2. The fan T simulates air flows such as those expected from an acoustic sensor housing 10 arranged on a vehicle traveling at a speed of approximately 30 km / h. Fig. 9 is compared to Fig. 8 less noisy; some noise patterns, for example, from a frequency of approximately 9 kHz, do not occur at all. Furthermore, the noise below a frequency of approximately 4 kHz is much narrower in band and at the same time the sound pressure level is lower in Fig. 9 than in Fig. 8. The narrowband frequency band of the Fig. 9, i.e., the acoustic sensor housing 10 disclosed here, allows for greater signal selectivity in signal processing, which translates into greater determinability or clarity of information. Broadband noise in the frequency range from 20 Hz to approximately 1.3 kHz has a lower sound pressure level in type B2 compared to type B1 and a sharper limitation at a frequency of 1.2 kHz.

[0043] Fig. 10, Fig. 11 shows frequency responses with fan T switched on and siren signal played as an audio file via sound source Q; Fig. 10 for type B1 and Fig. 11 for type B2. The test procedure corresponds to the test procedure described above. With the acoustic sensor housing 10 disclosed here, see Fig. 11, a higher selectivity of the siren signal tones is achieved. Furthermore, the siren signal tones obtained with type B2 are higher than with type B1. Starting at a frequency of approximately 4 kHz, type B2 achieves significantly better signal quality, with a gain of approximately 30 dB.

[0044] Fig. 12, Fig. 13 show frequency responses during real-life vehicle journeys at a speed of 50 km / h, with an acoustic sensor housing 10 with an acoustic sensor 21 mounted on the vehicle. The acoustic sensor housing 10 is arranged, for example, centrally on the vehicle roof above the windshield, with the opening 2 of the housing cover 1 facing in the direction of travel. Fig. 12 shows the results obtained with type B1, Fig. 13 the results obtained with type B2. The test drives with type B1 and type B2 were conducted under the same environmental conditions, in particular dry road surfaces and no wind. The result is essentially consistent with the result from Fig. 10, Fig. 11 agree. Reference symbol 10 acoustic sensor housings 1 housing cover 2 Opening 3 spherical bodies 4 Inflow component 5 sound channel 6 Downstream side 7 Membran 8 Flow bypass 9 Inner wall 20 Case back 21 Acoustic sensor A axial axis H Holding bridge R clamping device L circuit board M membrane lip D Sealing ring S Air flow direction W opening angle B1 Type 1 B2 Type 2 T fan 30 Data processing device Q Sound source

Claims

[1] Acoustic sensor housing (10) for detecting airborne sound in the exterior of vehicles moving in air fluid, the acoustic sensor housing (10) comprising a housing cover (1) comprising an opening (2) for air inlet that is symmetrical to an axial axis (A) of the acoustic sensor housing (10), a spherical body (3) arranged axially symmetrically in the opening (2), an inflow component (4) arranged behind the spherical body (3) in the air flow direction and comprising a sound channel (5) in the form of a continuous hollow space parallel to the axial axis (A), wherein the spherical body (3) is fixed to the inflow component (4) on an outflow side (6) by means of an acoustically permeable membrane (7) that protects the sound channel (5) against the action of foreign bodies, and wherein a flow bypass (8) that directs foreign bodies that have entered the acoustic sensor housing (10) through the air flow away from the membrane (7) out of the acoustic sensor housing (10) leads out,by a free space between the surface of the spherical body (3), the membrane (7), the inflow component (4) and an inner wall (9) of the housing cover (1). [2] Acoustic sensor housing (10) according to claim 1, wherein the spherical body (3) is fixed to the inflow component (4) by means of a holding web (H). [3] Acoustic sensor housing (10) according to claim 2, wherein the holding web (H) is fixed to the inflow component (4) by means of a clamping device (R). [4] Acoustic sensor housing (10) according to claim 2, wherein the holding web (H) is fixed to the inflow component (4) by means of a clamping device (R) and the holding web (H) and the clamping device (R) are designed as a monolithic part. [5] Acoustic sensor housing (10) according to claim 2, 3 or 4, wherein the retaining web (H) has perforations. [6] Acoustic sensor housing (10) according to one of the preceding claims, wherein the surface of the spherical body (3) comprises trough-shaped indentations. [7] Acoustic sensor housing (10) according to one of the preceding claims, comprising a housing base (20) onto which the housing cover (1) can be placed, wherein the housing base (20) comprises an acoustic sensor (21) which is in operative connection with the sound channel (5) when the housing cover (1) is placed on. [8] Acoustic sensor housing (10) according to one of the preceding claims, comprising a heating device which dehumidifies and / or defrosts the acoustic sensor housing (10). [9] Vehicle comprising one or more acoustic sensor housings (10) according to one of the preceding claims, wherein the acoustic sensor housings (10) are arranged on an outer skin of the vehicle. [10] Vehicle according to claim 9, comprising a driving system for automated driving functions, wherein acoustic sensors (21) accommodated in the acoustic sensor housings (10) perceive an environment of the vehicle and the driving system processes data from the acoustic sensors (21) for trajectory planning and / or trajectory control.

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