Sound / vibration detection device

Abstract

A sound / vibration detection device (100) is electrically connected to an acoustic sensor (20) attached to an external structure part (10) of a vehicle. The sound / vibration detection device (100) is provided with a sensor control section (40) and a signal processing unit (60). The sensor control section (40) causes a sound / vibration, obtained by converting a test signal (St), to be transmitted from a transmitter attached to the vehicle. The sensor control section (40) acquires a reception signal (Sr) of the sound / vibration of the test signal (St) measured by a receiver included in the acoustic sensor (20). The signal processing unit (60) executes processing for ascertaining the state of the acoustic sensor (20) on the basis of the reception signal (Sr).

Description

Sound vibration detection device Cross-reference to related applications

[0001] This application is based on Japanese Patent Application No. 2025-17191 filed in Japan on February 5, 2025, and the contents of the base application are incorporated herein by reference in their entirety.

[0002] The disclosure in this specification relates to a sound vibration detection device electrically connected to an acoustic sensor.

[0003] Patent Document 1 describes a transducer array mounted on a vehicle. This transducer array enables measurement of the distance between surrounding objects and the vehicle by transmitting and receiving acoustic signals such as ultrasonic waves.

[0004] International Publication No. 2016 / 184603

[0005] Acoustic signals include not only ultrasonic waves as disclosed in Patent Document 1 but also audible sounds and vibrations in the audible range. Consideration is being given to attaching an acoustic sensor for detecting such audible sounds or vibrations (hereinafter, sound vibrations) to a structural part of a vehicle. However, if an attempt is made to grasp the state of such an acoustic sensor, for example, the presence or absence of a failure and changes in sensor characteristics, etc., after the vehicle has been put into the market, dedicated inspection equipment such as a test speaker is required.

[0006] The present disclosure aims to provide a sound vibration detection device capable of easily grasping the state of an acoustic sensor.

[0007] To achieve the above object, one disclosed aspect is a sound vibration detection device electrically connected to an acoustic sensor attached to a structural part of a vehicle, the sound vibration detection device including: a sensor control unit that transmits a sound vibration obtained by converting a test signal from a transmitter attached to the vehicle and acquires a reception signal of the sound vibration of the test signal measured by a receiver included in the acoustic sensor; and a signal processing unit that executes a process for grasping the state of the acoustic sensor based on the reception signal.

[0008] In this configuration, a sound vibration converted from a test signal is transmitted from a transmitter mounted on the vehicle, and the received signal of this sound vibration is measured by the receiver of the acoustic sensor. Therefore, even after a vehicle equipped with the acoustic sensor is on the market, processing to determine the status of the acoustic sensor can be performed based on the received signal without the need for dedicated inspection equipment. Thus, it becomes possible to easily determine the status of the acoustic sensor.

[0009] Furthermore, the reference numbers in parentheses in the claims merely indicate an example of their correspondence with the specific configurations in the embodiments described later, and do not in any way limit the technical scope. In addition, combinations of claims not explicitly stated in the claims are also possible, provided that they do not cause any particular problems with the combination.

[0010] This figure illustrates the location on a vehicle where the acoustic sensor of this disclosure is mounted. This figure shows a sound vibration detection device according to the first embodiment of this disclosure, together with the acoustic sensor and speaker. This is a cross-sectional view showing the configuration of the acoustic sensor and speaker attached to the external structure. This figure shows a modified version of Figure 3. This figure shows another modified version of Figure 3. This figure shows yet another modified version of Figure 3. This is a block diagram showing the electrical configuration of the signal processing unit. This figure shows an example of a correction process for correcting a received signal. This figure shows another example of a correction process for correcting a received signal. This figure is for explaining the timing in which the test mode is performed. This figure is for explaining the white noise used as a test signal. This figure is for explaining the TSP signal used as a test signal. This figure shows the details of the process for calculating the cross-correlation function. This figure shows the details of another process for calculating the cross-correlation function. This figure shows the details of the process for determining a fault based on the cross-correlation function. This figure shows the details of the process for calculating a normalized cross-correlation function. This figure shows the process for determining a fault based on the normalized cross-correlation function. This figure shows the details of the process for calculating the frequency characteristics. This figure shows the details of another process for calculating the frequency characteristics. This figure explains the details of the process for calculating the sensor correction value from the frequency characteristics. This figure explains the details of another process for calculating the sensor correction value from the frequency characteristics. This figure shows the configuration of an acoustic detection system according to the second embodiment of this disclosure. This figure shows the operation of the acoustic detection system in test mode. This figure shows the process of calculating a sensor correction value based on frequency characteristics. This figure shows another process of calculating a sensor correction value based on frequency characteristics. This figure shows the configuration of an acoustic detection system according to the third embodiment of this disclosure. This figure shows the configuration of an acoustic detection system according to the fourth embodiment of this disclosure. This is a block diagram showing the electrical configuration of an acoustic sensor. This figure shows an example of the amplitude spectrum of a received signal. This figure shows the configuration of an acoustic detection system according to the fifth embodiment of this disclosure. This figure shows the mounting structure of the acoustic sensor to the external structure in the sixth embodiment. This figure shows the mounting structure of the acoustic sensor to the external structure in the seventh embodiment. This figure shows the mounting structure of the acoustic sensor to the external structure in the eighth embodiment. This is a cross-sectional view showing the configuration of an acoustic sensor according to the ninth embodiment.This is a cross-sectional view showing the configuration of an acoustic sensor according to the tenth embodiment. This is a cross-sectional view showing the configuration of an acoustic sensor according to the eleventh embodiment. This is a diagram showing the configuration of an acoustic detection system according to the twelfth embodiment. This is a diagram showing the configuration of an acoustic detection system according to the thirteenth embodiment. This is a diagram showing the configuration of an acoustic detection system according to the fourteenth embodiment. This is a diagram showing the configuration of an acoustic detection system according to the fifteenth embodiment. This is a diagram showing the configuration of an acoustic detection system according to the sixteenth embodiment.

[0011] Several embodiments will be described below with reference to the drawings. In each embodiment, the same reference numerals are used for corresponding components, and redundant explanations may be omitted. If only a part of the configuration is described in each embodiment, the configuration of other embodiments described earlier can be applied to the other parts of that configuration. Furthermore, in addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations from multiple embodiments can be partially combined even if not explicitly stated, as long as there are no particular problems with the combination.

[0012] [Mounting Position of Acoustic Sensor Device] The acoustic sensor 20 in this disclosure is mounted on the vehicle Ve, as shown in Figures 1 and 2. The acoustic sensor 20 can be set at various locations on the vehicle Ve, such as the front, side, rear, and glass surfaces of the vehicle. The acoustic sensor 20 is held in the plate-shaped external structure 10 of the vehicle Ve. If the acoustic sensor 20 is a piezoelectric sensor type, no opening is required in the external structure 10. On the other hand, if the acoustic sensor 20 is a microphone type, an opening (see mounting opening 15 in Figure 2) is formed in the external structure 10. The microphone-type acoustic sensor 20 is mounted flush with the opening or installed inside the vehicle via an acoustic path.

[0013] The external structural parts 10 on the front of the vehicle include, for example, the central part Pf1 of the front bumper and the corner parts Pf2 of the front bumper. The acoustic sensor 20 installed on the external structural parts 10 on the front of the vehicle is positioned with its transmitting / receiving surface 22a facing forward Ze of the vehicle Ve, and is used to detect objects that emit sound mainly in the forward Ze area outside of the vehicle Ve. Sounds here include emergency vehicle sirens, road noise from the vehicle Ve, collision sounds from the vehicle Ve, human voices, railroad crossing sounds, vehicle Ve horns, train whistles, etc.

[0014] The external structural parts 10 on the side of the vehicle include, for example, the front bumper side part Ps1, the rear bumper side part Ps2, the side mirror cover Ps3, and the side step Ps4. The acoustic sensor 20 installed on the external structural parts 10 on the side of the vehicle is positioned with its transmitting / receiving surface 22a facing either the right (Mi) or left (Hi) of the vehicle Ve, and is used to detect objects that emit sound mainly from the side outside the vehicle Ve.

[0015] The external structural parts 10 on the rear of the vehicle include, for example, the central part Pb1 and the corner parts Pb2 of the rear bumper. The acoustic sensor 20 installed on the external structural parts 10 on the rear of the vehicle is positioned with its transmitting / receiving surface 22a facing the rear Go of the vehicle Ve, and is used to detect objects outside the vehicle Ve that mainly emit sounds from the rear Go.

[0016] The external structural part 10 of the vehicle glass surface includes, for example, the lower edge Pg1 of the windshield, the upper edge Pg3 of the windshield, and the upper edge Pg2 of the rear glass, the lower edge P4 of the rear glass, etc. The acoustic sensor 20 installed on the external structural part 10 of the vehicle glass surface is positioned with its transmitting / receiving surface 22a aligned with the glass surface and is used to detect objects that emit sound in the direction of the vehicle Ve (Ze) or the direction of the vehicle's rear (Go).

[0017] Here, the longitudinal and lateral directions in this disclosure are defined with respect to a vehicle Ve stationary on a horizontal plane. Specifically, the longitudinal direction (forward Ze and rearward Go) is defined along the longitudinal direction (direction of travel) of the vehicle Ve. The lateral direction (rightward Mi and leftward Hi) is defined along the width direction of the vehicle Ve. Furthermore, the vertical direction (upward Ue) is defined along the vertical direction of the horizontal plane that defines the longitudinal and lateral directions. For the sake of simplicity, the symbols indicating each direction may be omitted in the following explanation as appropriate.

[0018] (First Embodiment) The sound vibration detection device 100 according to the first embodiment of the present disclosure shown in Figure 2 is electrically connected to a speaker 121 and an acoustic sensor 20. The sound vibration detection device 100, together with the speaker 121 and the acoustic sensor 20, constitutes an acoustic detection system. The sound vibration detection device 100 is connected in a star configuration to the speaker 121 and the acoustic sensor 20 via an analog line 130. The sound vibration detection device 100 is capable of analog transmission with the speaker 121 and the acoustic sensor 20.

[0019] The speaker 121 and acoustic sensor 20 shown in Figures 2 and 3 are attached to the external structure 10 of the vehicle Ve. The external structure 10 is, for example, a front bumper or a rear bumper, and is formed from a resin material such as polypropylene in a flat or slightly curved plate shape. The external structure 10 may also be a glass panel of the vehicle Ve (see Figure 1). The external structure 10 forms the vehicle outer surface 11 that is exposed to the outside of the vehicle Ve when facing forward Ze, rear Go, or to the side of the vehicle Ve. On the external structure 10, the back side of the vehicle outer surface 11 is a smooth vehicle inner surface 12 to which an adhesive layer is attached.

[0020] Speaker 121 is a dedicated speaker provided for the acoustic detection system. Speaker 121 has a transmitting element 21a and a drive circuit 24. The transmitting element 21a is capable of transmitting audible sounds from its transmitting surface 122a. The transmitting element 21a is housed in a mounting opening 15 provided in the external structure 10. The mounting opening 15 is a through hole that penetrates the external structure 10 in the thickness direction. The transmitting surface 122a of speaker 121 is exposed on the vehicle outer surface 11 side of the external structure 10.

[0021] The drive circuit 24 is electrically connected to the sound vibration detection device 100 and the transmitting element 21a. The drive circuit 24 drives the transmitting element 21a based on the analog signal input from the sound vibration detection device 100. The drive circuit 24 generates sound by applying a voltage to the transmitting element 21a, causing vibration in the transmitting element 21a. The drive circuit 24 amplifies the analog signal (for example, a test signal St, etc.) and supplies it to the transmitting element 21a1. As a result, the transmitting element 21a generates mechanical vibrations corresponding to the test signal St, etc.

[0022] The acoustic sensor 20 is attached to the external structure 10 via an adhesive layer. The adhesive layer is formed as a thin film thinner than the external structure 10 using double-sided tape or adhesive. Each surface of the adhesive layer is bonded to the vehicle's inner surface 12 of the external structure 10 and to the receiving surface 122b of the acoustic sensor 20, respectively. The acoustic sensor 20 is fixed to the vehicle's inner surface 12 by the adhesive layer.

[0023] The acoustic sensor 20 is a sound-vibration sensor that detects at least one of audible sounds (air vibrations) and vibrations (solid vibrations). The audible range is a frequency band lower than ultrasound, specifically the range from 20 Hz to 20 kHz. In the following description, at least one of the audible sounds and vibrations measured by the acoustic sensor 20 will be referred to as "sound vibrations." The acoustic sensor 20 consists of a receiving element 21b, a housing 22, and a receiving circuit 27, etc.

[0024] The receiving element 21b is, for example, a piezoelectric element (piezoelectric element) formed in the shape of a thin plate. A piezoelectric element generates an electric charge when subjected to mechanical stress. The receiving element 21b is a transducer that functions as a receiver, converting sound vibrations in the audible range into electrical signals. The receiving element 21b has a receiving surface 122b of the acoustic sensor 20 formed on it.

[0025] The housing 22 houses the receiving element 21b and the receiving circuit 27. The housing 22 is formed in a flat cylindrical or prismatic shape from a resin material such as polybutylene terephthalate (PBT). The housing 22 is held to the inner surface 12 of the vehicle via an adhesive layer. At least a portion of the receiving surface 122b may be formed by the bottom surface of the housing 22.

[0026] The receiving circuit 27 measures the terminal voltage Vt of the receiving element 21b. The receiving circuit 27 detects the electrical signal generated when the receiving element 21b receives sound vibrations. The receiving circuit 27 has an amplifier function that amplifies the electrical signal (analog signal) output from the receiving element 21b and a filter function that removes unwanted noise contained in the analog signal. The analog signal output from the receiving circuit 27 (for example, the received signal Sr, etc.) is output to the sound vibration detection device 100.

[0027] [Modified Speaker Configuration] Speaker 121 may function as an approach notification speaker that notifies other vehicles and pedestrians in the vicinity of the approach of vehicle Ve, and may be configured to transmit an audible approach notification sound. In this configuration, speaker 121 transmits the sound vibration of a test signal St, described later, superimposed on the approach notification sound. Alternatively, as shown in Figure 4, speaker 121 may be a vibration speaker that uses a voice coil or piezoelectric element in the transmitting element 21a that vibrates the vehicle structure 10 to generate audible sound. In this modified configuration, the transmitting surface 122a of the transmitting element 21a is attached to the inner surface 12 of the vehicle.

[0028] In addition, the speaker 121 may be configured for in-car audio, as shown in Figure 5. In this modified configuration, the sound radiated from the transmitting surface 122a of the transmitting element 21a strikes the inner surface 12 of the vehicle, causing vibrations in the external structure 10.

[0029] Furthermore, the speaker 121 may be integrally configured with the acoustic sensor 20, as shown in Figure 6. In other words, the components of the speaker 121 are built into the acoustic sensor 20. In this modified example, the transmitting element 21a, which is made of a piezoelectric element, and the drive circuit 24 are housed in the housing 22 of the acoustic sensor 20.

[0030] [Configuration of the Sound and Vibration Detection Device] The sound and vibration detection device 100 shown in Figure 2 is an on-board computer mounted on the vehicle Ve. The sound and vibration detection device 100 is an external processing unit provided separately from the speaker 121 and the acoustic sensor 20. The sound and vibration detection device 100 uses the acoustic sensor 20 installed on the vehicle Ve to detect sounds (external sounds) coming from around the vehicle Ve, vibrations caused by external sounds hitting the external structure 10, and vibrations caused when the vehicle Ve comes into contact with an object. The sound and vibration detection device 100 monitors external sounds and vibrations coming to the vehicle Ve in real time, enabling detection of approaching specific objects (e.g., emergency vehicles), detection of vehicle malfunctions, detection of abnormalities occurring around the vehicle, and understanding of road conditions. The sound and vibration detection device 100 may be a dedicated ECU (electronic control unit) that processes the detection results of the acoustic sensor 20, or it may be an integrated ECU with additional functions. For example, an integrated ECU such as a driver assistance ECU, an autonomous driving ECU, an image recognition ECU, an infotainment ECU, and a zone ECU or multimedia control unit may also be equipped with the functions of a sound vibration detection device 100.

[0031] The sound vibration detection device 100 comprises a sensor control unit 40 and a signal processing unit 60. The sensor control unit 40 includes a signal generation unit 44 and an analog-to-digital converter (hereinafter referred to as ADC) 45. The signal generation unit 44 generates a specific electrical signal (for example, a test signal St, etc.) and outputs it to the drive circuit 24 of the speaker 121. The signal generation unit 44 also supplies the same digital signal as the electrical signal supplied to the drive circuit 24 to the signal processing unit 60. The ADC 45 receives a received signal Sr, etc., output by the receiving circuit 27 of the acoustic sensor 20. The ADC 45 converts the received analog signal into a digital signal and outputs it to the signal processing unit 60.

[0032] The signal processing unit 60 shown in Figures 2 and 7 is configured primarily with a controller that has high computing processing power, such as a System on Chip (SoC) and a Digital Signal Processor (DSP). The signal processing unit 60 processes the output signal (received signal Sr) based on the detection result of at least one acoustic sensor 20. The functions of the signal processing unit 60 may be provided by a single dedicated chip such as an ASIC, or by an electrical circuit that combines multiple IC chips. The signal processing unit 60 includes a fast Fourier transform (FFT) function unit 60a and an arithmetic processing unit 60b, etc.

[0033] The FFT function unit 60a is connected to the signal generation unit 44 and the ADC 45. The FFT function unit 60a obtains a test signal St from the signal generation unit 44. The FFT function unit 60a obtains a received signal Sr from the ADC 45. The FFT function unit 60a converts the input time-domain electrical signal into the frequency domain. The FFT function unit 60a outputs the test signal St and the received signal Sr, etc., converted into the frequency domain, to the arithmetic processing unit 60b.

[0034] The arithmetic processing unit 60b analyzes the electrical signal acquired from the FFT function unit 60a for each frequency component and extracts information such as signal strength and phase. The arithmetic processing unit 60b is configured with a function corresponding to the operating mode of the sound vibration detection device 100. The operating modes of the sound vibration detection device 100 include a normal measurement mode for measuring ambient sound (see Figures 8 and 9) and a test mode for understanding the state of the acoustic sensor 20 (see Figures 2 and 3, etc.).

[0035] [Operation of the sound vibration detection device in normal measurement mode] First, the operation of the sound vibration detection device 100 in normal measurement mode will be explained. In normal measurement mode, the receiving element 21b of the acoustic sensor 20 is used to measure ambient sound. In normal measurement mode, the speaker 121 and the signal generation unit 44 are stopped. Meanwhile, in normal measurement mode, the receiving circuit 27 detects the electrical signal generated by the receiving element 21b that receives ambient sound, and outputs the detection result as a received signal Sr to the ADC 45. The ADC 45 acquires the received signal Sr, converts the acquired received signal Sr into a digital signal, and outputs it sequentially to the FFT function unit 60a.

[0036] When the sound vibration detection device 100 operates in normal measurement mode, a signal correction unit 64 is constructed in the arithmetic processing unit 60b of the signal processing unit 60. The signal correction unit 64 corrects the received signal Sr, which has been converted to the frequency domain by the FFT function unit 60a, using a correction value (hereinafter referred to as the sensor correction value) for correcting the frequency characteristics of the acoustic sensor 20. The sensor correction value is prepared in log format, which expresses the power (amplitude) of the sound vibration on a 10-base logarithm.

[0037] As an example, the signal correction unit 64 converts the sensor correction value into linear format and applies it to the received signal Sr (see Figure 6). In this case, the signal correction unit 64 outputs the linear power spectrum as the corrected received signal Sr. As another example, the signal correction unit 64 converts the received signal Sr acquired in linear format into log format (see Figure 7). The signal correction unit 64 applies the sensor correction value (corrected power spectrum) prepared in log format to the received signal Sr (power spectrum before correction) converted to log format. The signal correction unit 64 outputs the log power spectrum (corrected power spectrum) as the corrected received signal Sr.

[0038] [Operation of the sound vibration detection device in test mode] Next, the operation of the sound vibration detection device 100 in test mode will be explained. In test mode, the frequency characteristics of each acoustic sensor 20 are measured. In test mode, a fault detection process is performed to detect a malfunction in the acoustic sensor 20, and a characteristic correction process is performed to correct changes in the frequency characteristics of the acoustic sensor 20. The sound vibration detection device 100 starts test mode under predetermined conditions.

[0039] Specifically, the sound and vibration detection device 100 operates in test mode when the power supply of the vehicle Ve is switched from an inactive state such as standby, pause, or idle to an ON state (active state). The sound and vibration detection device 100 repeats operation in test mode during the period after the power supply has been switched to the ON state, while the vehicle Ve is stationary and the engine mounted on the vehicle Ve is stopped. The sound and vibration detection device 100 may also operate in test mode after the vehicle Ve has started moving, if the vehicle Ve's speed is below a threshold speed (for example, 10 to 20 km / h) or if the engine is stopped.

[0040] The sound vibration detection device 100 operates in test mode if the specified conditions are met, and then performs calculation processing for fault detection and correction value update based on the information acquired in the previous test mode (see Figure 10). After the sound vibration detection device 100 continues to operate in normal measurement mode for a predetermined time, if the specified conditions are still met, it performs operation in test mode and calculation processing for fault detection and correction value update. As described above, during the period in which the specified conditions are met, the sound vibration detection device 100 repeats operation in test mode at a fixed period (test mode period).

[0041] In the test modes shown in Figures 2 to 6, the sensor control unit 40 generates a test signal St using the signal generation unit 44. The test signal St is an electrical signal whose frequency components are not singular; in other words, an electrical signal with a wide bandwidth of frequency components that are spread over time. For example, white noise and TSP (Transport Stream Packet) signals can be used as test signals St. White noise is a signal in which frequency components in a specific band are evenly distributed (see Figure 11). A TSP signal is a signal whose frequency transitions from, for example, 24 kHz to 50 Hz over 4 seconds. The start frequency, end frequency, and transition time are appropriate signals that take into account the speaker and ADC characteristics (see Figure 12). Impulse signals, pink noise, and M-sequence signals may also be used as test signals St.

[0042] The sensor control unit 40 outputs the test signal St generated by the signal generation unit 44 to the speaker 121, causing the transmitting element 21a to transmit sound vibrations converted from the test signal St. The speaker 121 performs sound wave radiation (OH) in the audible range. In configurations where the speaker 121 is not exposed to the vehicle's outer surface 11, the speaker 121 generates structural vibrations (KS) in the external structure 10 (see Figures 4 to 6).

[0043] The acoustic sensor 20 measures, with the receiving element 21b, at least one of the sound wave radiation OH and the structural vibration KS generated by the speaker 121. The acoustic sensor 20 detects at least one of the sound wave propagation OD and the vibration transmission SD from the speaker 121. The sensor control unit 40 acquires a received signal Sr of the sound vibration measured by the receiving element 21b of the acoustic sensor 20, which is a received signal Sr based on the test signal St.

[0044] The signal processing unit 60 executes a process for grasping the state of the acoustic sensor 20 based on the received signal Sr and the test signal St. As described above, in the test mode, the failure detection process and the characteristic correction process are performed. Hereinafter, the details of each process will be described in order.

[0045] <Failure Detection Process> As shown in FIGS. 13 to 15, the signal processing unit 60 includes a correlation calculation unit 71, an inverse Fourier transform unit (hereinafter, inverse FFT) 72, an envelope conversion unit 73, a maximum point detection unit 74, and a failure detection unit 75 as functional units for the failure detection process.

[0046] The correlation calculation unit 71 (see also FIG. 7) acquires the frequency characteristics (Fourier spectra) of the received signal Sr and the test signal St respectively from the FFT functional unit 60a, and calculates the cross-correlation function of the two frequency characteristics. The correlation calculation unit 71 uses the test signal St acquired from the signal generation unit 44 as the reference signal StE. The reference signal StE is a signal corresponding to the test signal St. The correlation calculation unit 71 calculates the cross-correlation function of the received signal Sr and the reference signal StE acquired under the above-described specified conditions. The correlation calculation unit 71 acquires the received signal Sr and the reference signal StE converted into the frequency domain by the FFT functional unit 60a. The correlation calculation unit 71 calculates the cross-correlation function by an arithmetic process of multiplying the received signal Sr in the frequency domain by the complex conjugate (conjugate spectrum) of the reference signal StE (see the formula in FIG. 13).

[0047] The correlation calculation unit 71 may calculate the cross-correlation function by performing an arithmetic operation of multiplying the power spectrum of the reference signal StE by the frequency characteristic obtained by dividing the frequency characteristic (Fourier spectrum) of the received signal Sr by the frequency characteristic of the reference signal StE. This arithmetic operation corresponds to the operation of multiplying the transfer function (frequency characteristic) by the power spectrum of the reference signal StE.

[0048] Here, the complex conjugate of the reference signal StE does not change. Therefore, the correlation calculation unit 71 stores the calculated complex conjugate of the reference signal StE in the memory 63 (see FIG. 14). The correlation calculation unit 71 can also read out the complex conjugate (conjugate reference signal) stored in the memory 63, multiply the received signal Sr converted into the frequency domain by the FFT function unit 60a by the complex conjugate of the read reference signal StE, and calculate the cross-correlation function.

[0049] The inverse FFT 72 and the envelope converter 73 perform post-processing on the cross-correlation function at the subsequent stage of the correlation calculation unit 71 (see FIG. 15). The inverse FFT 72 converts the cross-correlation function in the frequency domain calculated by the correlation calculation unit 71 into the time domain. The envelope converter 73 converts the cross-correlation function converted into the time domain by the inverse FFT 72 into an envelope signal.

[0050] The maximum point detection unit 74 detects the value and time of the maximum point generated in the envelope signal of the cross-correlation function (see the amplitude waveform in FIG. 15). The time of the maximum point (hereinafter, the specific maximum point) showing the highest value during normal times is generally determined by the positional relationship (distance) between the speaker 121 and the acoustic sensor 20.

[0051] The fault detection unit 75 (see also Figure 7) detects a fault in the acoustic sensor 20 based on the cross-correlation function. The fault detection unit 75 detects a fault in the acoustic sensor 20 based on the value and time of the maximum point occurring in the envelope signal of the cross-correlation function. The fault detection unit 75 compares the value and time of the maximum point obtained from the current measurement with a pre-prepared reference value and time of the maximum point. When characteristic measurement in test mode is repeated under specified conditions, the fault detection unit 75 compares the amplitude waveforms (values ​​and times of the maximum point) of multiple cross-correlation functions calculated by the correlation calculation unit 71 with the amplitude waveform of the reference cross-correlation function and makes a fault determination. The fault detection unit 75 determines that the acoustic sensor 20 is faulty if the value of a specific maximum point determined by the positional relationship of the two acoustic sensors 20 falls below a predetermined threshold.

[0052] Furthermore, the amplitude waveforms during normal operation and those during failure, as shown in the lower right of Figure 15, have different vertical axis ranges. Specifically, the vertical axis scale during failure is approximately half that of the vertical axis scale during normal operation. In addition, the reference maximum point value and time are based on data acquired when the acoustic sensor 20 is calibrated, for example, at the time of factory shipment or during parts replacement at a dealer.

[0053] Furthermore, as shown in Figure 16, the signal processing unit 60 may calculate a normalized cross-correlation function. As an example, the cross-correlation function calculated by the correlation calculation unit 71 is divided by the amplitudes of the reference signal StE and the received signal Sr (see upper part of Figure 16). In another example, the reference signal StE and the received signal Sr2, which have been converted to the frequency domain by the FFT function unit 60a, are normalized by an operation that divides them by the amplitudes of their respective frequency domains (see lower part of Figure 16). The correlation calculation unit 71 calculates a cross-correlation function based on each normalized signal. This normalization prepares a normalized correlation function between 0 and 1 that excludes the effect of amplitude. Therefore, even when the reference signal StE and the received signal Sr are small or excessive, it becomes possible to make a judgment using a common judgment value. Even when using a normalized cross-correlation function, the maximum point detection unit 74 and the fault detection unit 75 can determine a fault in the acoustic sensor 20 by the disappearance of a specific maximum point from the amplitude waveform (see Figure 17).

[0054] <Characteristic Correction Processing> As shown in Figures 18 to 21, the signal processing unit 60 includes a characteristic calculation unit 81 and a correction value calculation unit 82 as functional units for characteristic correction processing (see also Figure 7).

[0055] The characteristic calculation unit 81 obtains the received signal Sr and test signal St, converted to the frequency domain, from the FFT function unit 60a. The characteristic calculation unit 81 calculates the frequency characteristics of the acoustic sensor 20 using the received signal Sr and test signal St. The characteristic calculation unit 81 uses the test signal St obtained from the signal generation unit 44 as the reference signal StE. The characteristic calculation unit 81 calculates the frequency characteristics of the acoustic sensor 20 using the received signal Sr and reference signal StE obtained under the above-described specified conditions. The characteristic calculation unit 81 calculates the frequency characteristics (transfer function) of the acoustic sensor 20 by performing an operation that divides the received signal Sr in the frequency domain by the reference signal StE in the frequency domain (see the formula in Figure 18).

[0056] Here, the reference signal StE remains largely unchanged. Therefore, the characteristic calculation unit 81 calculates the reciprocal of the reference signal StE converted to the frequency domain and stores the calculated reciprocal of the reference signal StE in the memory 63 (see Figure 19). The characteristic calculation unit 81 reads out the reciprocal of the reference signal StE stored in the memory 63. The characteristic calculation unit 81 can also calculate the frequency characteristics of the acoustic sensor 20 by multiplying the received signal Sr converted to the frequency domain by the FFT function unit 60a by the reciprocal of the reference signal StE read out (see the formula in Figure 19).

[0057] The correction value calculation unit 82 calculates a sensor correction value based on the frequency characteristics of each acoustic sensor 20. The sensor correction value is provided to the correction value update unit 67 and stored in the memory 63. In the normal measurement mode described above, the sensor correction value is provided from the correction value update unit 67 to the signal correction unit 64 and used to correct the received signal Sr (see Figure 7).

[0058] As shown in Figure 20, the correction value calculation unit 82 converts the frequency characteristics obtained from the characteristic calculation unit 81 into an amplitude spectrum or power spectrum in the process of calculating the sensor correction value. The correction value calculation unit 82 smooths the waveform by removing high-frequency components from the amplitude spectrum or power spectrum of the frequency characteristics using a low-pass filter. The correction value calculation unit 82 calculates the sensor correction value by performing a logarithmic transformation, subtracting the amplitude (log) of the reference frequency, and inverting the sign. In this way, by using the amount of deviation of the frequency characteristics of the received signal Sr from the reference frequency (e.g., 1 kHz) as the sensor correction value, the corrected frequency characteristics can be flattened.

[0059] Furthermore, as shown in Figure 21, the correction value calculation unit 82 can obtain a smoothing effect similar to that of a low-pass filter by combining multiple bins of the amplitude spectrum (frequency-amplitude characteristics) of the frequency characteristics, thereby using the sum or average value of the amplitude values ​​as the sensor correction value. This method makes it possible to reduce the number of bins. In detail, when the number of sampling points of the FFT function unit 60a is N (N = 2^n), this N is the number of bins. In the calculation of the frequency characteristics, the conjugate component is removed, resulting in a number of bins of 2^(n-1) + 1. The correction value calculation unit 82 reduces the number of bins to 2^(n-m-1) by a "2^m average" process. As a result, the number of bins (number of parameters) in the sensor correction value is also reduced to 2^(n-m-1). Thus, the computational amount of the process for calculating the sensor correction value and the correction process using the sensor correction value can be reduced. In addition, the capacity of the recording area for the sensor correction value can be reduced.

[0060] The correction value calculation unit 82 calculates a sensor correction value that reflects the current state of the acoustic sensor 20 by combining a dynamic correction component calculated using the frequency characteristics acquired in test mode with a reference initial correction component. As an example, the correction value calculation unit 82 uses the three most recent sensor correction values ​​C'(f)[0] to C'(f)[2] as the dynamic correction component. In addition, the correction value calculation unit 82 uses the sensor correction value Cb(f) acquired when the acoustic sensor 20 is calibrated at the time of factory shipment or when parts are replaced at a dealer as the reference initial correction component. As shown in Equation 1 below, the correction value calculation unit 82 uses the average value of the sensor correction values ​​C'(f)[0] to C'(f)[2] and Cb(f) as the sensor correction value C''(f) provided to the correction value calculation unit 82 (see Figure 5). (Equation 1) C''(f) = (Cb(f) + C'(f)[0] + C'(f)[1] + C'(f)[2]) / 4

[0061] Furthermore, the correction value calculation unit 82 may, without using an initial correction component, use the average value of the most recent multiple (for example, four) sensor correction values ​​as the sensor correction value provided to the correction value calculation unit 82, as shown in Equation 2 below. This process can prevent excessive correction caused by measurement variability. (Equation 2) C''(f) = (C'(f)[0] + C'(f)[1] + C'(f)[2] + C'(f)[3]) / 4

[0062] The fault detection unit 75 (see Figures 7 and 13) determines that the acoustic sensor 20 is faulty if the sum of the dynamic correction components exceeds a predetermined threshold. Furthermore, the fault detection unit 75 may determine that the acoustic sensor 20 is faulty by comparing the sensor correction value, which is the initial correction component, with the sensor correction value, which is the dynamic correction component. Specifically, the fault detection unit 75 determines that the sensor is faulty if any frequency bin of the latest sensor correction value, the sum of frequency bins within a predetermined frequency band, or the overall value of the frequency bins of the sensor correction value deviates by a predetermined value or more.

[0063] (Summary of the First Embodiment) In the first embodiment described above, a sound vibration converted from a test signal St is transmitted from a transmitting element 21a attached to the vehicle Ve, and the received signal Sr of this sound vibration is measured by the receiving element 21b of the acoustic sensor 20. Therefore, even after the vehicle Ve with the acoustic sensor 20 attached is distributed to the market, processing to understand the state of the acoustic sensor 20 can be performed based on the received signal Sr without using dedicated inspection equipment. Thus, it becomes possible to easily understand the state of the acoustic sensor 20.

[0064] As described above, in the first embodiment, the characteristics of the acoustic sensor 20 can be measured even after the acoustic sensor 20 has been installed on the vehicle Ve. Furthermore, the characteristics of the acoustic sensor 20 can be measured without requiring inspection equipment for characteristic measurement (e.g., a test speaker). Moreover, the characteristics of the acoustic sensor 20 can be measured even at a factory that manufactures or maintains the vehicle Ve.

[0065] In addition, in a modified version of the first embodiment (see Figure 6), the transmitting element 21a is included in the acoustic sensor 20. This configuration simplifies the configuration of the acoustic detection system and reduces the mounting space.

[0066] In the first embodiment, the correlation calculation unit 71 calculates a cross-correlation function based on the received signal Sr and the reference signal StE corresponding to the test signal St (see Figure 13). The fault detection unit 75 then detects a fault in the acoustic sensor 20 based on the cross-correlation function. With this configuration, abnormalities such as detachment of the acoustic sensor 20 can be detected after installation. Furthermore, since faults are detected based on the cross-correlation function, misidentification of faults caused by external noise can be suppressed.

[0067] Furthermore, in the first embodiment, the characteristic calculation unit 81 calculates the frequency characteristics of the acoustic sensor 20 using the received signal Sr and a reference signal StE corresponding to the test signal St. Then, the fault detection unit 75 detects a fault in the acoustic sensor 20 based on the frequency characteristics of the acoustic sensor 20. Even with fault determination using such frequency characteristics, misidentification of faults caused by disturbance noise can be suppressed.

[0068] In addition, in the first embodiment, the correction value calculation unit 82 calculates a sensor correction value based on the frequency characteristics of the acoustic sensor 20 calculated by the characteristic calculation unit 81. Then, the signal correction unit 64 corrects the received signal Sr using the sensor correction value. With this configuration, it becomes possible to suppress characteristic fluctuations of the acoustic sensor 20 after installation.

[0069] The signal processing unit 60 of the first embodiment further includes an inverse FFT 72, an envelope converter 73, and a maximum point detection unit 74. The inverse FFT 72 converts the cross-correlation function calculated by the correlation calculation unit 71 into a time domain. The envelope converter 73 converts the cross-correlation function converted into the time domain by the inverse FFT 72 into an envelope signal. The maximum point detection unit 74 detects the value and time of the maximum point occurring in the envelope signal. Then, the fault detection unit 75 detects a fault in the acoustic sensor 20 based on the value and time of the maximum point occurring in the envelope signal. This processing based on the maximum point of the cross-correlation function eliminates the effects of multipath and disturbances. As a result, the accuracy of fault detection can be further improved.

[0070] Furthermore, in the first embodiment, when the power supply of the vehicle Ve is switched on, the sound vibration of the test signal St is transmitted from the transmitting element 21a. The sensor control unit 40 acquires a received signal Sr measured by the receiving element 21b from the sound vibration caused by this test signal St. The signal processing unit 60 uses the received signal Sr acquired when the power supply is switched on to determine the state of the acoustic sensor 20. As described above, by measuring the received signal Sr based on the test signal St when the vehicle Ve is stopped immediately after the power supply is switched on, the influence of disturbances such as driving noise and engine noise can be reduced.

[0071] In addition, in the first embodiment, when the vehicle Ve's driving speed is below a threshold speed, the sound vibration of the test signal St is transmitted from the transmitting element 21a. The sensor control unit 40 acquires a received signal Sr measured by the receiving element 21b from the sound vibration caused by this test signal St. The signal processing unit 60 uses the received signal Sr acquired when the driving speed is below the threshold speed to determine the state of the acoustic sensor 20. As described above, by measuring the received signal Sr based on the test signal St during periods of low driving speed, the effects of wind noise and road noise can be reduced.

[0072] In the first embodiment, when the engine mounted on the vehicle Ve is stopped, the sound vibration of the test signal St is transmitted from the transmitting element 21a. The sensor control unit 40 acquires a received signal Sr measured by the receiving element 21b from the sound vibration caused by this test signal St. The signal processing unit 60 uses the received signal Sr acquired when the engine is stopped to determine the state of the acoustic sensor 20. As described above, by measuring the received signal Sr based on the test signal St during the period when the engine is stopped, the effects of engine vibration and noise can be reduced.

[0073] Furthermore, in a configuration where speaker 121 transmits an approach notification sound to notify those around the vehicle of the vehicle's approach, the sensor control unit 40 can superimpose the sound vibration of the test signal St onto the approach notification sound and transmit it from speaker 121. With this configuration, the sound vibration converted from the test signal St can be masked by the approach notification sound. In particular, if the test signal St is white noise or pink noise, these sound vibrations are easily masked by the approach notification sound. As a result, the sound vibration of the test signal St is less likely to be perceived as bothersome by the vehicle Ve user or pedestrians around the vehicle.

[0074] In addition, the characteristic calculation unit 81 of the first embodiment calculates the frequency characteristics of the acoustic sensor 20 using the received signal Sr and the test signal St (reference signal StE) acquired under predetermined conditions. The correction value calculation unit 82 combines the dynamic correction component calculated using the frequency characteristics with the reference initial correction component to calculate a sensor correction value that reflects the current state of the acoustic sensor 20. In this way, by using the initial correction component measured in an environment with little disturbance, such as a factory inspection area, as the basis, it is possible to avoid situations in which a sensor correction value that is too far off is applied.

[0075] In the first embodiment described above, the external structural part 10 corresponds to the "structural part," the transmitting element 21a corresponds to the "transmitter," and the receiving element 21b corresponds to the "receiver."

[0076] (Second Embodiment) The acoustic detection system of the second embodiment shown in Figures 22 to 25 is a modified version of the first embodiment. In the acoustic detection system of the second embodiment, each of the multiple acoustic sensors 20 attached to the same external structure 10 is used for transmitting and receiving the test signal St. The sound vibration detection device 100 is connected to the multiple acoustic sensors 20 in a star configuration via communication cables. The sound vibration detection device 100 is capable of analog communication with the multiple acoustic sensors 20.

[0077] The acoustic sensor 20 is composed of a transmitting / receiving element 21, a drive circuit 24, a receiving circuit 27, and a housing 22 that accommodates these components. The transmitting / receiving element 21 is formed from a thin-plate piezoelectric element or the like, similar to the receiving element 21b in the first embodiment. The transmitting / receiving element 21 has the function of a transmitter that converts electrical signals into audible sound vibrations and the function of a receiver that converts audible sound vibrations into electrical signals. The transmitting / receiving surface 22a of the acoustic sensor 20 is formed on the transmitting / receiving element 21.

[0078] The drive circuit 24 operates the transmitting / receiving element 21 as a transmitting element 21a. Specifically, the drive circuit 24 generates sound by applying a voltage to the transmitting / receiving element 21, thereby generating vibrations in the transmitting / receiving element 21. The drive circuit 24 amplifies the analog signal (test signal St, etc.) received from the sensor control unit 40 and supplies it to the transmitting / receiving element 21. As a result, the transmitting / receiving element 21 functions as a transmitting element 21a, generating mechanical vibrations corresponding to the test signal St, etc.

[0079] The receiving circuit 27 causes the transmitting / receiving element 21 to function as a receiving element 21b. The receiving circuit 27 has amplifier and filter functions, similar to the first embodiment. The receiving circuit 27 outputs analog signals (for example, received signals Sr1, Sr2, etc.) based on measurements using the transmitting / receiving element 21 to the sensor control unit 40.

[0080] [Operation of the sound vibration detection device in test mode] As shown in Figures 22 and 23, the sensor control unit 40 causes one of the multiple acoustic sensors 20 to function as a transmitter in test mode. The sensor control unit 40 operates the transmitting / receiving element 21 of one acoustic sensor 20 (first sensor 20a) as a transmitting element 21a that transmits the sound vibration of the test signal St.

[0081] The sensor control unit 40 outputs the test signal St generated by the signal generation unit 44 to the first sensor 20a, causing the transmitting element 21a included in the first sensor 20a to transmit sound vibrations converted from the test signal St. The first sensor 20a emits sound waves OH in the audible range and generates structural vibrations KS in the external structure 10.

[0082] The sensor control unit 40 causes the acoustic sensors 20 other than the first sensor 20a (the second sensor 20b) to function as receivers. The second sensor 20b uses the transmitting / receiving element 21 as the receiving element 21b and measures the sound wave radiation OH and structural vibration KS generated by the first sensor 20a. The second sensor 20b detects the sound wave propagation OD and vibration transmission SD from the first sensor 20a. The second sensor 20b acquires a received signal Sr2 based on the test signal St from the receiving element 21b and outputs it to the ADC 45 of the sensor control unit 40.

[0083] The sensor control unit 40 continuously and periodically transmits the sound vibration of a test signal St from one acoustic sensor 20 and measures the sound vibration of the test signal St using another acoustic sensor 20, under predetermined conditions. In one test mode, the sensor control unit 40 swaps among multiple acoustic sensors 20 that transmit the sound vibration converted from the test signal St from the transmitting element 21a and acoustic sensors 20 that measure the sound vibration of the test signal St with the receiving element 21b.

[0084] More specifically, the sensor control unit 40 first outputs a test signal St generated by the signal generation unit 44 associated with the first sensor 20a to the drive circuit 24 of the first sensor 20a (see Figure 22). The drive circuit 24 applies the test signal St to the transmitting and receiving element 21, generating sound vibrations (sound wave radiation OH and structural vibration KS, etc.) based on the test signal St.

[0085] The receiving circuit 27 of the second sensor 20b detects sound wave propagation OD and vibration transmission SD using the transmitting / receiving element 21 and generates a received signal Sr2 that measures sound vibration based on the test signal St. The receiving circuit 27 transfers the received signal Sr2, which is an analog signal, to the ADC 45 associated with the second sensor 20b. As a result, the frequency characteristics of the second sensor 20b are measured.

[0086] When the sensor control unit 40 has finished measuring the characteristics of the second sensor 20b, it starts measuring the characteristics of the first sensor 20a. The sensor control unit 40 switches the signal generation unit 44 that generates the test signal St and causes the signal generation unit 44 associated with the second sensor 20b to start generating the test signal St (see Figure 23). The sensor control unit 40 outputs the test signal St generated by the signal generation unit 44 to the drive circuit 24 of the second sensor 20b. The drive circuit 24 applies the test signal St to the transmitting and receiving element 21 and generates sound vibrations based on the test signal St.

[0087] The receiving circuit 27 of the first sensor 20a detects sound wave propagation OD and vibration transmission SD using the transmitting / receiving element 21 and generates a received signal Sr1 that measures sound vibration based on the test signal St. The receiving circuit 27 transfers the received signal Sr1, which is an analog signal, to the ADC 45 associated with the first sensor 20a. As a result, the frequency characteristics of the first sensor 20a are measured.

[0088] The correlation calculation unit 71 (see Figures 7 and 13, etc.) calculates multiple cross-correlation functions based on the received signals Sr1 and Sr2 measured by the multiple acoustic sensors 20. Specifically, the correlation calculation unit 71 calculates at least one cross-correlation function based on the received signal Sr1 and the reference signal StE, and another cross-correlation function based on the received signal Sr2 and the reference signal StE.

[0089] In addition, the characteristic calculation unit 81 (see Figures 7 and 18) individually calculates the frequency characteristics of the multiple acoustic sensors 20 connected to the sensor control unit 40. Specifically, when the first sensor 20a operates as a transmitter and the second sensor 20b functions as a receiver, the characteristic calculation unit 81 calculates the "frequency characteristic 1-2" of the second sensor 20b based on the received signal Sr2 and the reference signal StE (see Figure 22). Conversely, when the second sensor 20b operates as a transmitter and the first sensor 20a functions as a receiver, the characteristic calculation unit 81 calculates the "frequency characteristic 2-1" of the first sensor 20a based on the received signal Sr1 and the reference signal StE (see Figure 23).

[0090] The correction value calculation unit 82 (see Figures 7 and 20) may calculate a sensor correction value that is used in common for multiple acoustic sensors 20 based on the frequency characteristics associated with each acoustic sensor 20, or it may calculate individual sensor correction values ​​associated with each acoustic sensor 20.

[0091] As an example, the correction value calculation unit 82 calculates a sensor correction value that is commonly applied to the first sensor 20a and the second sensor 20b, etc., based on the "frequency characteristics 1-2" and "frequency characteristics 2-1" obtained from the characteristic calculation unit 81 (see Figure 24). As another example, the correction value calculation unit 82 calculates the sensor correction value for each acoustic sensor 20 by weighting "frequency characteristics 1-2" and "frequency characteristics 2-1" and then performing an averaging process (see Figure 24). More specifically, when calculating the "sensor correction value 2" associated with the second sensor 20b, the correction value calculation unit 82 gives a greater weight to "frequency characteristics 1-2" than to "frequency characteristics 2-1" (see upper part of Figure 24). Conversely, when calculating the "sensor correction value 1" associated with the first sensor 20a, the correction value calculation unit 82 gives a greater weight to "frequency characteristics 2-1" than to "frequency characteristics 1-2" (see lower part of Figure 24).

[0092] When the correction value calculation unit 82 calculates the "sensor correction value 2" associated with the second sensor 20b, it may set the weighting of "frequency characteristic 2-1" to zero. That is, the "sensor correction value 2" may be calculated using only "frequency characteristic 1-2" among the multiple frequency characteristics. Similarly, when calculating the "sensor correction value 1" associated with the first sensor 20a, the correction value calculation unit 82 may set the weighting of "frequency characteristic 1-2" to zero. That is, the "sensor correction value 1" may be calculated using only "frequency characteristic 2-1" among the multiple frequency characteristics.

[0093] (Summary of the second embodiment) In the second embodiment described above, the sound vibration obtained by converting the test signal St is transmitted from the transmitting element 21a, and the received signals Sr1 and Sr2 of this sound vibration are measured by the receiving element 21b. Therefore, even after the vehicle Ve to which the acoustic sensor 20 is attached is distributed to the market, processing to understand the state of the acoustic sensor 20 can be performed using the test signal St and its received signals Sr1 and Sr2.

[0094] In addition, in the second embodiment, the sensor control unit 40 inputs a test signal St to the transmitter and acquires the received signals Sr1 and Sr2 output from the receiver. Furthermore, in a test mode for executing processing to understand the state of the acoustic sensor 20, the sensor control unit 40 operates the acoustic sensor 20 as a transmitter that transmits the sound vibrations of the test signal St. On the other hand, in a normal measurement mode for measuring ambient sound, the sensor control unit 40 operates the acoustic sensor 20 as a receiver that receives ambient sound. With this configuration, it becomes unnecessary to mount a dedicated transmitter (e.g., a speaker) on the vehicle Ve to transmit the sound vibrations converted from the test signal St. As a result, the configuration of the acoustic detection system can be simplified and the mounting space can be reduced.

[0095] In the second embodiment, the transmitting and receiving element 21 of the acoustic sensor 20 operates as a transmitter in test mode. On the other hand, in normal measurement mode, the transmitting and receiving element 21 operates as a receiver. As described above, with a configuration in which the transmitting and receiving element 21 serves as both a transmitter and a receiver, the acoustic sensor 20 can be miniaturized, and its mountability on the vehicle Ve can be improved.

[0096] Furthermore, the sensor control unit 40 of the second embodiment is electrically connected to a plurality of acoustic sensors 20. In addition, in test mode, the sensor control unit 40 swaps among the plurality of acoustic sensors 20 that transmit sound vibrations converted from the test signal St from the transmitter and acoustic sensors 20 that measure the sound vibrations of the test signal St with the receiver. By swapping the transmitter and receiver, multiple cross-correlation functions can be obtained, which can improve the accuracy of fault detection. In addition, since multiple frequency characteristics can be obtained, the accuracy of the sensor correction value can improve.

[0097] In addition, in the second embodiment, multiple acoustic sensors 20 are attached to the same external structure 10. For example, if multiple acoustic sensors 20 are attached to the same external structure 10, such as a bumper and a glass panel, vibration transmission SD from the transmitter to the receiver can be generated stably. As a result, the signal processing unit 60 can accurately measure the frequency characteristics.

[0098] Furthermore, the characteristic calculation unit 81 of the second embodiment calculates the frequency characteristics of each acoustic sensor 20 using the received signals Sr1 and Sr2 and the test signal St (reference signal StE). Then, the correction value calculation unit 82 calculates a sensor correction value associated with each acoustic sensor 20 based on the frequency characteristics. By preparing individual sensor correction values ​​associated with each acoustic sensor 20, a high level of accuracy in signal correction in normal measurement mode can be ensured.

[0099] Furthermore, the correction value calculation unit 82 of the second embodiment calculates a sensor correction value that is used in common for multiple acoustic sensors 20 based on the frequency characteristics associated with each acoustic sensor 20. By using a sensor correction value common to multiple acoustic sensors 20 in this way, the processing load of signal correction in the normal measurement mode can be reduced.

[0100] In addition, in the second embodiment, under predetermined conditions, the transmission of sound vibrations of the test signal St from the transmitter and the measurement of sound vibrations of the test signal St by the receiver are continuously and periodically performed by the acoustic sensor 20. By continuing periodic measurements in this way, it is possible to avoid misjudgments of faults due to sudden disturbances and calculations of inappropriate correction values.

[0101] In the second embodiment described above, the transmitting / receiving element 21 corresponds to a "conversion element," the transmitting element 21a corresponds to a "transmitter," and the receiving element 21b corresponds to a "receiver."

[0102] (Third Embodiment) The acoustic detection system of the third embodiment shown in Figure 26 is a modified version of the second embodiment. In the acoustic detection system of the third embodiment, the sound vibration detection device 100 is connected to each of the plurality of acoustic sensors 20 in a digital manner for high-speed communication. The communication between the sound vibration detection device 100 and each acoustic sensor 20 may be half-duplex or full-duplex.

[0103] The sensor control unit 40 of the sound vibration detection device 100 further has a plurality of communication interfaces 41. Each communication interface 41 is individually connected to the sensor control unit 40. The communication interface 41 transfers the digital signal of the test signal St generated by the signal generation unit 44 to the acoustic sensor 20. The communication interface 41 acquires the digital signal of the received signal Sr transferred by the acoustic sensor 20. The communication interface 41 outputs the acquired received signal Sr to the FFT function unit 60a.

[0104] The acoustic sensor 20 further includes a communication interface 26, a digital-to-analog converter (DAC) 25, and an ADC 28. The communication interface 26 is digitally connected to the communication interface 41 of the sound vibration detection device 100. In addition, the communication interface 26 is digitally connected to the DAC 25 and the ADC 28. The communication interface 26 acquires the digital signal of the test signal St transmitted by the communication interface 41 and outputs it to the DAC 25.

[0105] The DAC 25 is electrically connected to the communication interface 26 and the drive circuit 24. The DAC 25 converts the test signal St input by the communication interface 26 into an analog signal and inputs it to the drive circuit 24.

[0106] The ADC 28 is electrically connected to the receiving circuit 27 and the communication interface 26. The ADC 28 converts the analog signals Sr1 and Sr2 received from the transmitting and receiving elements 21 into digital signals and outputs them to the communication interface 26. The received signals Sr1 and Sr2 are then transferred as digital signals to the sound vibration detection device 100 via the communication interface 26.

[0107] (Summary of the Third Embodiment) In the third embodiment described above, the sound vibration obtained by converting the test signal St is transmitted from the transmitting element 21a, and the received signals Sr1 and Sr2 of this sound vibration are measured by the receiving element 21b. This provides the same effect as in the second embodiment, and even after the vehicle Ve to which the acoustic sensor 20 is attached is distributed to the market, processing to understand the state of the acoustic sensor 20 can be performed using the test signal St and its received signals Sr1 and Sr2.

[0108] In addition, the sensor control unit 40 of the third embodiment has a communication interface 41 that is electrically connected to the acoustic sensor 20. The communication interface 41 acquires the received signals Sr1 and Sr2 transmitted from the acoustic sensor 20 by communication. With this connection configuration, it is possible to suppress the effects of noise and have the sound vibration detection device 100 acquire high-quality received signals Sr1 and Sr2.

[0109] (Fourth Embodiment) The acoustic detection system of the fourth embodiment shown in Figure 27 is a modified version of the third embodiment. In the acoustic detection system of the fourth embodiment, the sensor control unit 40 of the sound vibration detection device 100 has a transmission instruction unit 46 and a signal memory 47. The transmission instruction unit 46 works in conjunction with the communication interface 41 to transmit an output instruction for the test signal St to the acoustic sensor 20. The transmission instruction unit 46 stores data related to the reference signal StE corresponding to the test signal St, specifically the complex conjugate of the reference signal StE and the reciprocal of the reference signal StE. When the transmission instruction unit 46 issues an output instruction for the test signal St, the signal memory 47 provides the stored data to the signal processing unit 60.

[0110] The DAC 25 of the acoustic sensor 20 further has a signal generation function that generates a test signal St. Based on the fact that the output instruction for the test signal St has been acquired by the communication interface 26, the DAC 25 generates the test signal St, which is an analog signal, and outputs it to the drive circuit 24.

[0111] The receiving circuit 27 of the acoustic sensor 20 measures the terminal voltage Vt of the transmitting / receiving element 21 during the period when the driving circuit 24 operates the transmitting / receiving element 21 as a transmitter in response to the test signal St (see Figure 28). The receiving circuit 27 sequentially outputs the measurement result of the terminal voltage Vt to the ADC 28. The ADC 28 converts the analog signal, which is the measurement result of the terminal voltage Vt, into a digital signal and outputs it to the communication interface 26. The communication interface 26 transfers the digital signal indicating the measurement result of the terminal voltage Vt as a received signal Sr to the sensor control unit 40.

[0112] The sensor control unit 40 outputs the acquired received signal Sr to the signal processing unit 60. The fault detection unit 75 of the signal processing unit 60 (see Figures 7 and 13, etc.) determines a fault in the acoustic sensor 20 driven by the test signal St, based on the received signal Sr. As an example, the fault detection unit 75 calculates the amplitude spectrum of the received signal Sr (see Figure 29). The fault detection unit 75 refers to the amplitude spectrum and detects the voltage width at the resonant frequency or anti-resonant frequency. If the voltage width at the resonant frequency or anti-resonant frequency expands beyond a predetermined threshold from a reference state, the fault detection unit 75 determines that a fault such as sensor detachment has occurred in the acoustic sensor 20.

[0113] In another example, the TSP signal is used as a test signal St to drive the acoustic sensor 20. In the TSP signal, the frequency changes linearly or nonlinearly over time. In this case, the fault detection unit 75 acquires the amplitude waveform of the received signal Sr. Based on the change in the amplitude waveform of the received signal Sr, the fault detection unit 75 determines that a fault has occurred in the acoustic sensor 20.

[0114] (Summary of the fourth embodiment) In the fourth embodiment described so far, the same effects as in the above embodiments are achieved, and even after the vehicle Ve to which the acoustic sensor 20 is attached is distributed to the market, processing to understand the state of the acoustic sensor 20 can be performed using the test signal St and its received signals Sr1 and Sr2.

[0115] In addition, the acoustic sensor 20 of the fourth embodiment includes a transmitting / receiving element 21, a drive circuit 24 that operates the transmitting / receiving element 21 as a transmitter, and a receiving circuit 27 that makes the transmitting / receiving element 21 function as a receiver. The sensor control unit 40 acquires the terminal voltage Vt of the transmitting / receiving element 21 measured by the receiving circuit 27 during the period when the drive circuit 24 operates the transmitting / receiving element 21 as a transmitter in response to a test signal St, as a received signal Sr. The fault detection unit 75 detects a fault in the acoustic sensor 20 based on the amplitude waveform or frequency characteristics of this received signal Sr. As described above, by using the actually measured terminal voltage Vt as the received signal Sr, the accuracy of fault detection can be improved.

[0116] (Fifth Embodiment) The acoustic detection system of the fifth embodiment shown in Figure 30 is another modification of the third embodiment. In the acoustic detection system of the fifth embodiment, the sound vibration detection device 100 and the plurality of acoustic sensors 20 are digitally connected to a communication bus 30 for constructing an in-vehicle network. The sound vibration detection device 100 and the acoustic sensors 20 form a bus-type communication network through electrical connection with the communication bus 30. The sound vibration detection device 100 and each acoustic sensor 20 may form a daisy-chain type communication network.

[0117] The communication bus 30 enables data communication between the sound vibration detection device 100 and each acoustic sensor 20. Communication between the sound vibration detection device 100 and each acoustic sensor 20 via the communication bus 30 may be half-duplex or full-duplex. For communication connections between the sound vibration detection device 100 and each acoustic sensor 20, a communication bus 30 based on data communication standards such as LIN, DSI3, and CAN (Controller Area Network, registered trademark) is used. In addition, a communication bus 30 based on high-speed serial communication standards such as A2B, USB, LVDS, and Ethernet (registered trademark) may be used for communication connections between the sound vibration detection device 100 and the acoustic sensors 20.

[0118] Multiple slots are formed in the communication interface 41 of the sensor control unit 40. For example, slots 1 to 4 are assigned to the outputs of test signals St1 to St4, which are output to each acoustic sensor 20. Slots 5 to 8 are assigned to the inputs of received signals Sr1 to Sr4, which are transferred from each acoustic sensor 20.

[0119] The signal generation unit 44 generates test signals St1 to St4 to be transferred to each acoustic sensor 20. The signal generation unit 44 outputs address information indicating the acoustic sensor 20 to which the test signals St1 to St4 will be transferred, along with the generated test signals St1 to St4, to the communication interface 41. The communication interface 41 transmits the test signal St to the acoustic sensor 20 indicated by the address information. In addition, the communication interface 41 acquires the received signals Sr1 to Sr4 transferred from each acoustic sensor 20 and outputs the acquired received signals Sr1 to Sr4 to the FFT function unit 60a.

[0120] (Summary of the Fifth Embodiment) The fifth embodiment described so far also has the same effects as the second to fourth embodiments, and even after the vehicle Ve to which the acoustic sensor 20 is attached is distributed to the market, processing to understand the state of the acoustic sensor 20 can be performed using the test signals St1 to St4 and their received signals Sr1 to Sr4.

[0121] In addition, the sensor control unit 40 of the fifth embodiment has a communication interface 41 that is electrically connected to a plurality of acoustic sensors 20 via a communication bus 30. The communication interface 41 acquires received signals Sr1 to Sr4 transferred from each acoustic sensor 20 by communication. With this connection configuration, it is possible to suppress the effects of noise and have the sound vibration detection device 100 acquire high-quality received signals Sr1 to Sr4.

[0122] (Sixth to Eighth Embodiments) In the sixth to eighth embodiments, multiple acoustic sensors 20 are attached to the external structure 10, similar to the second embodiment. In the fourth to sixth embodiments, the mounting structure of the acoustic sensors 20 to the external structure 10 differs from that of the second embodiment.

[0123] More specifically, in the sixth embodiment shown in Figure 31, the first sensor 20a is attached to the external structure 10 using an exposed mounting method. The first sensor 20a is housed in a mounting opening 15 provided in the external structure 10, with its transmitting / receiving surface 22a exposed to the vehicle's outer surface 11. In contrast, the second sensor 20b is attached to the external structure 10 using an adhesive mounting method. The transmitting / receiving surface 22a of the second sensor 20b is attached to the vehicle's inner surface 12 with double-sided tape or the like.

[0124] In the seventh embodiment shown in Figure 32, the first sensor 20a is attached to the external structure 10 using an adhesive mounting method. The transmitting / receiving surface 22a of the first sensor 20a is attached to the inner surface 12 of the vehicle with double-sided tape or the like. In contrast, the second sensor 20b is attached to the external structure 10 using an exposed mounting method. The second sensor 20b is housed in a mounting opening 15 provided in the external structure 10, with its transmitting / receiving surface 22a exposed to the outer surface 11 of the vehicle.

[0125] In the eighth embodiment shown in Figure 33, both the first sensor 20a and the second sensor 20b are mounted to the external structure 10 using an exposed mounting method. The first sensor 20a and the second sensor 20b are housed in mounting openings 15 provided in the external structure 10, with their transmitting and receiving surfaces 22a exposed to the vehicle's outer surface 11.

[0126] In the sixth to eighth embodiments described so far, in test mode, either the first sensor 20a or the second sensor 20b operates as a transmitter, and in normal measurement mode, both the first sensor 20a and the second sensor 20b can operate as receivers. As a result, processing to understand the state of the acoustic sensor 20 can be performed without requiring the addition of a dedicated transmission configuration.

[0127] (Ninth to Eleventh Embodiments) In the ninth to eleventh embodiments, the internal structure of the acoustic sensor 20 connected to the sound vibration detection device 100 differs from that of the embodiments described above. Specifically, in the acoustic sensor 20 of the ninth embodiment shown in Figure 34, a transmitting element 21a and a receiving element 21b are housed in a single housing 22. In test mode, the transmitting element 21a of one acoustic sensor 20 (for example, the first sensor 20a) transmits sound vibrations converted from the test signal St. Meanwhile, the receiving element 21b of the acoustic sensor 20 that transmits the sound vibrations of the test signal St, as well as the transmitting element 21a and receiving element 21b of the other acoustic sensor 20 (for example, the second sensor 20b), output received signals Sr11, Sr22, and Sr21. The other acoustic sensors 20 may have their transmitting element 21a inactive.

[0128] In the acoustic sensor 20 of the tenth embodiment shown in Figure 35, a transmitting element 21a and a receiving element 21b are housed in a single housing 22. The housing 22 partitions an isolation space 22c. The isolation space 22c is located between the transmitting element 21a and the receiving element 21b. The isolation space 22c acoustically separates the transmitting element 21a and the receiving element 21b. The isolation space 22c may be filled with a filler such as silicone rubber or foamed urethane. In test mode, the acoustic sensor 20 transmits sound vibrations converted from a test signal St from the transmitting element 21a. The acoustic sensor 20 measures the sound vibrations caused by the test signal St with the receiving element 21b and outputs a received signal Sr2. As described above, in the tenth embodiment, the measurement of frequency characteristics in test mode can be completed with a single acoustic sensor 20.

[0129] In the eleventh embodiment shown in Figure 36, acoustic sensors 20 having substantially the same configuration as in the tenth embodiment are attached to the external structure 10 as a first sensor 20a, a second sensor 20b, etc. In test mode, similar to the ninth embodiment, the transmitting element 21a of one acoustic sensor 20 (for example, the first sensor 20a) transmits sound vibrations converted from the test signal St. Meanwhile, the receiving element 21b of the acoustic sensor 20 that transmits the sound vibrations of the test signal St, and the transmitting element 21a and receiving element 21b of the other acoustic sensor 20 (for example, the second sensor 20b), output received signals Sr11, Sr22, and Sr21. The other acoustic sensors 20 may have their transmitting element 21a inactive.

[0130] As described in the ninth to eleventh embodiments above, by providing a piezoelectric element for transmission and a piezoelectric element for reception only in the acoustic sensor 20, and by switching the operation of the transmitter and receiver using a sound vibration detection device 100 (see Figure 22), the transmission performance and reception performance can be improved.

[0131] (Twelfth Embodiment) In the acoustic detection system of the twelfth embodiment shown in Figure 37, an FFT 61 is provided in the sensor circuit section 23 of each acoustic sensor 20. The acoustic sensor 20 converts the received signals Sr1 and Sr2 measured by the transmitting and receiving elements 21 into frequency domain signals using the FFT 61. The acoustic sensor 20 transfers the received signals Sr1 and Sr2 converted to the frequency domain to the communication interface 41 via the communication bus 30. The communication interface 41 outputs the acquired received signals Sr1 and Sr2 to the signal processing unit 60. The signal processing unit 60 uses the received signals Sr1 and Sr2, which have been converted to the frequency domain in advance, to perform fault detection processing and characteristic correction processing in the arithmetic processing unit 60b.

[0132] As described in the twelfth embodiment above, if an FFT 61 is provided for each acoustic sensor 20, it becomes possible to reduce the load on the signal processing unit 60.

[0133] (Third Embodiment) In the acoustic detection system of the thirteenth embodiment shown in Figure 38, an FFT 61 and a microcontroller 120 are provided in the sensor circuit section 23 of each acoustic sensor 20. The acoustic sensor 20 transmits (broadcasts) the received signals Sr1 and Sr2, which have been converted to the frequency domain by the FFT 61, to other acoustic sensors 20 via the communication bus 30. The acoustic sensor 20 performs fault detection processing and characteristic correction processing using the microcontroller 120.

[0134] More specifically, the microcontroller 120 has functions equivalent to the signal processing unit 60 of the first embodiment, etc. The microcontroller 120 is equipped with a correlation calculation unit 71, an inverse FFT 72, a fault detection unit 75, and functional units such as a characteristic calculation unit 81 and a correction value calculation unit 82 (see Figures 7 and 13, etc.). Furthermore, the microcontroller 120 has a signal correction unit 64 (see Figure 7) that corrects the received signals Sr1 and Sr2 using sensor correction values.

[0135] As described in the thirteenth embodiment, if each acoustic sensor 20 is equipped with an FFT 61 and a microcontroller 120, it becomes possible to reduce the load on the controller 160 of the sound vibration detection device 100. In the thirteenth embodiment, the acoustic detection system including the acoustic sensors 20 corresponds to the "sound vibration detection device".

[0136] (Fourteenth Embodiment) In the fourteenth embodiment shown in Figure 39, similar to the thirteenth embodiment, an FFT 61 and a microcontroller 120 are provided in the sensor circuit section 23 of each acoustic sensor 20. The microcontroller 120 performs processing to compress the amount of data of the received signals Sr1 and Sr2 (reduce the number of bins), such as averaging, Mel-spectral conversion, and DCT conversion. The acoustic sensor 20 converts the received signals Sr1 and Sr2 into the frequency domain using the FFT 61, and the microcontroller 120 performs calculations to combine multiple bins of the received signals Sr1 and Sr2. The acoustic sensor 20 transfers the compressed received signals Sr1 and Sr2 to the communication interface 41 of the sound vibration detection device 100 via the communication bus 30.

[0137] As described in the fourteenth embodiment, if each acoustic sensor 20 is equipped with an FFT 61 and a microcontroller 120 to compress the data of the received signals Sr1 and Sr2, it becomes possible to reduce the communication load and computation load. In the fourteenth embodiment, the acoustic detection system including the acoustic sensors 20 corresponds to the "sound vibration detection device".

[0138] (Fifteenth and Sixteenth Embodiments) In the acoustic detection system of the fifteenth embodiment shown in Figure 40, each acoustic sensor 20 and the sound vibration detection device 100 are electrically connected through a single analog line 130. In the fourteenth embodiment, the transmission communication line and the reception communication line are combined into a single analog line 130. Each acoustic sensor 20 and the sound vibration detection device 100 transmit and receive information using ASK communication, FSK communication, PSK communication, etc., using a bandwidth of 48 kHz or higher.

[0139] In ASK (Amplitude Shift Keying) communication, information is transmitted by AM modulation, which changes the amplitude of the analog signal. In FSK (Frequency Shift Keying) communication, information is transmitted by FM modulation, which changes the frequency of the analog signal. In PSK (Phase Shift Keying) communication, information is transmitted by PM modulation, which changes the phase of the analog signal.

[0140] In the sensor circuit section 23 of the acoustic sensor 20 of the fifteenth embodiment, a signal generation unit 44 is provided in addition to a drive circuit 24, a receiving circuit 27, and a communication interface 26. The sensor control unit 40 transmits a transmission command StC for a test signal St to one acoustic sensor 20 (first sensor 20a, etc.). When the acoustic sensor 20 receives the transmission command StC via the communication interface 26, the signal generation unit 44 generates the test signal St. The drive circuit 24 drives the transmitting and receiving element 21 (see Figure 28) using the test signal St input from the signal generation unit 44. The acoustic sensor 20 transfers the received signals Sr1 and Sr2 generated by the receiving circuit 27 to the sensor control unit 40 via the communication interface 26 and the analog line 130.

[0141] In the acoustic detection system of the sixteenth embodiment shown in Figure 41, each acoustic sensor 20 and the sound vibration detection device 100 are electrically connected via a communication bus 30. The sensor circuit section 23 of the acoustic sensor 20 is provided with a drive circuit 24, a receiving circuit 27, and a communication interface 26, as well as a signal generation unit 44, an FFT 61, and a microcontroller 120. The communication interface 41 of the sound vibration detection device 100 transmits a transmission command StC of a test signal St to a specific acoustic sensor 20 (first sensor 20a, etc.).

[0142] When the acoustic sensor 20 receives a transmission command StC via the communication interface 26, the signal generation unit 44 generates a test signal St. The drive circuit 24 drives the transmitting and receiving elements 21 (see Figure 28) based on the test signal St received from the signal generation unit 44. The acoustic sensor 20 converts the received signals Sr1 and Sr2 generated by the receiving circuit 27 into frequency domain signals using an FFT 61. The microcontroller 120 performs processing such as encoding and data compression of the received signals Sr1 and Sr2. The received signals Sr1 and Sr2 processed by the microcontroller 120 are transferred to the communication interface 41 of the sound vibration detection device 100 via the communication interface 26.

[0143] As described in the fifteenth and sixteenth embodiments above, the signal generation unit 44 may be provided in the sensor circuit unit 23 of each acoustic sensor 20. Also, as in the sixteenth embodiment, if the FFT 61 and microcontroller 120 are provided in the sensor circuit unit 23, the communication load of the communication bus 30 and the computation load of the controller 160 can be reduced. In the sixteenth embodiment, the acoustic detection system including the acoustic sensor 20 corresponds to the "sound vibration detection device".

[0144] (Other Embodiments) Although several embodiments of the present disclosure have been described above, the present disclosure is not to be construed as being limited to the above embodiments, and can be applied to various embodiments and combinations without departing from the spirit of the present disclosure.

[0145] In the above embodiment, a piezoelectric element was used as the transmitting / receiving element 21. Such a transmitting / receiving element 21 may also include a configuration including a diaphragm and a coil, a configuration including a capacitor consisting of a diaphragm and a fixed electrode, or a configuration including a MEMS (Micro-Electro-Mechanical Systems).

[0146] The vehicle Ve equipped with the acoustic sensor 20 is not limited to a typical private passenger car, but may include rental cars, manned taxis, ride-sharing vehicles, cargo vehicles, buses, etc. Furthermore, the acoustic sensor 20 can be installed in autonomous vehicles used for mobility services. In addition, the number and location of the acoustic sensors 20 are appropriately optimized according to the form of the vehicle Ve, the intended use of the vehicle Ve, and the traffic environment and regulations of the country or region in which the vehicle Ve is used.

[0147] In the above embodiment, each function provided by the signal processing unit 60 and the microcontroller 120, etc., can also be provided by software and the hardware that executes it, software only, hardware only, or a combination thereof. Furthermore, when such functions are provided by electronic circuits as hardware, each function can also be provided by digital circuits including a large number of logic circuits, or by analog circuits.

[0148] (Disclosure of Technical Ideas) This specification discloses several technical ideas as described in the following paragraphs. Some paragraphs may be written in a multiple dependent form, where subsequent paragraphs optionally refer to preceding paragraphs. Furthermore, some paragraphs may be written in a multiple dependent form, where they refer to other multiple dependent forms. These paragraphs written in multiple dependent forms define several technical ideas.

[0149] (Technical Concept 1) A sound vibration detection device electrically connected to an acoustic sensor (20) attached to a structural part (10) of a vehicle (Ve), comprising: a sensor control unit (40) that transmits sound vibrations converted from a test signal (St) from a transmitter attached to the vehicle and acquires a received signal (Sr) of the sound vibrations of the test signal measured by a receiver included in the acoustic sensor; and a signal processing unit (60) that performs processing to understand the state of the acoustic sensor based on the received signal. (Technical Concept 2) The sound vibration detection device according to Technical Concept 1, wherein the transmitter is included in the acoustic sensor. (Technical Concept 3) The sound vibration detection device according to Technical Concept 1 or 2, wherein the signal processing unit comprises: a correlation calculation unit (71) that calculates a cross-correlation function based on the received signal and the test signal or a reference signal (StE) corresponding to the test signal; and a fault detection unit (75) that detects a fault in the acoustic sensor based on the cross-correlation function. (Technical Idea 4) The sound vibration detection device according to any one of Technical Ideas 1 to 3, comprising: a characteristic calculation unit (81) that calculates the frequency characteristics of the acoustic sensor using the received signal and the test signal or a reference signal (StE) corresponding to the test signal; and a fault detection unit (75) that detects a fault in the acoustic sensor based on the frequency characteristics of the acoustic sensor. (Technical Idea 5) The sound vibration detection device according to any one of Technical Ideas 1 to 4, comprising: a characteristic calculation unit (81) that calculates the frequency characteristics of the acoustic sensor using the received signal and the test signal or a reference signal corresponding to the test signal; a correction value calculation unit (82) that calculates a sensor correction value based on the frequency characteristics of the acoustic sensor; and a signal correction unit (64) that corrects the received signal using the sensor correction value.(Technical Idea 6) The sound vibration detection device according to any one of Technical Ideas 1 to 5, wherein the sensor control unit operates the acoustic sensor as the transmitter that transmits the sound vibration of the test signal in a test mode for performing processing to understand the state of the acoustic sensor, and operates the acoustic sensor as the receiver that receives the ambient sound in a normal measurement mode for measuring ambient sound. (Technical Idea 7) The sound vibration detection device according to Technical Idea 6, wherein the sensor control unit operates the conversion element (21) of the acoustic sensor as the transmitter in the test mode, and operates the conversion element as the receiver in the normal measurement mode. (Technical Idea 8) The sound vibration detection device according to any one of Technical Ideas 1 to 7, wherein the sensor control unit is electrically connected to a plurality of acoustic sensors, and in a test mode for performing processing to understand the state of the acoustic sensors, the acoustic sensor that transmits the sound vibration converted from the test signal from the transmitter and the acoustic sensor that measures the sound vibration of the test signal with the receiver are interchangeable among the plurality of acoustic sensors. (Technical Idea 9) A sound vibration detection device according to Technical Idea 8, wherein a plurality of acoustic sensors are attached to the same structural part and electrically connected. (Technical Idea 10) A sound vibration detection device according to Technical Idea 5, wherein the sensor control unit is electrically connected to a plurality of acoustic sensors, and in a test mode for measuring the frequency characteristics, the acoustic sensor that transmits the sound vibration converted from the test signal from the transmitter and the acoustic sensor that measures the sound vibration of the test signal with the receiver are interchanged among the plurality of acoustic sensors, the characteristic calculation unit calculates the frequency characteristics of each acoustic sensor using the received signal and the test signal or a reference signal (StE) corresponding to the test signal, and the correction value calculation unit calculates the sensor correction value used in common to the plurality of acoustic sensors based on the frequency characteristics associated with each acoustic sensor.(Technical Concept 11) The sound vibration detection device according to Technical Concept 3, wherein the sensor control unit is electrically connected to the acoustic sensor which includes a conversion element (21), a drive circuit (24) that operates the conversion element as the transmitter, and a receiving circuit (27) that causes the conversion element to function as the receiver, and the receiving circuit acquires the terminal voltage (Vt) of the conversion element measured by the receiving circuit during the period when the drive circuit operates the conversion element as the transmitter by the test signal as the received signal, and the fault detection unit detects a fault in the acoustic sensor based on the amplitude waveform of the received signal or the frequency characteristics of the received signal. (Technical Idea 12) The signal processing unit further includes an inverse Fourier transformer (72) that converts the cross-correlation function calculated by the correlation calculation unit into a time domain, an envelope transformer (73) that converts the cross-correlation function converted into the time domain by the inverse Fourier transformer into an envelope signal, and a maximum point detection unit (74) that detects the value and time of the maximum point occurring in the envelope signal, wherein the fault detection unit detects a fault in the acoustic sensor based on the value and time of the maximum point occurring in the envelope signal, as described in Technical Idea 3. (Technical Idea 13) The sound vibration detection device according to any one of Technical Ideas 1 to 12, wherein the sensor control unit has a communication interface, the communication interface is electrically connected to a plurality of acoustic sensors via a communication bus (30), and the received signal transmitted from each acoustic sensor is acquired by communication. (Technical Concept 14) The sound vibration detection device according to any one of Technical Concepts 1 to 13, wherein the sensor control unit causes the sound vibration of the test signal to be transmitted from the transmitter when the power of the vehicle is switched on, and the receiver obtains the received signal measured by the receiver, and the signal processing unit uses the received signal obtained when the power is switched on to determine the state of the acoustic sensor.(Technical Concept 15) The sound vibration detection device according to any one of Technical Concepts 1 to 14, wherein the sensor control unit causes the sound vibration of the test signal to be transmitted from the transmitter when the vehicle's driving speed is below a threshold speed, and the receiver acquires the received signal measured by the receiver, and the signal processing unit uses the received signal acquired when the driving speed is below the threshold speed to determine the state of the acoustic sensor. (Technical Concept 16) The sound vibration detection device according to any one of Technical Concepts 1 to 15, wherein the sensor control unit causes the sound vibration of the test signal to be transmitted from the transmitter when the engine mounted on the vehicle is stopped, and the receiver acquires the received signal measured by the receiver, and the signal processing unit uses the received signal acquired when the engine is stopped to determine the state of the acoustic sensor. (Technical Concept 17) The sound vibration detection device according to any one of Technical Concepts 1 to 16, wherein the sensor control unit transmits the sound vibration of the test signal from the transmitter in conjunction with an approach warning sound that notifies those around the vehicle of the vehicle's approach. (Technical Concept 18) A sound vibration detection device according to any one of Technical Concepts 1 to 17, wherein the sensor control unit causes the acoustic sensor to continuously and periodically transmit the sound vibration of the test signal from the transmitter and measure the sound vibration of the test signal by the receiver under predetermined conditions. (Technical Concept 19) A sound vibration detection device according to Technical Concept 5, wherein the sensor control unit causes the sound vibration of the test signal to be transmitted from the transmitter under predetermined conditions, and the receiver obtains the received signal measured by the receiver; the characteristic calculation unit calculates the frequency characteristics of the acoustic sensor using the received signal obtained under the conditions and the test signal or the reference signal; and the correction value calculation unit calculates the sensor correction value that reflects the current state of the acoustic sensor by combining a dynamic correction component calculated using the frequency characteristics and a reference initial correction component.

Claims

1. A sound vibration detection device electrically connected to an acoustic sensor (20) attached to a structural part (10) of a vehicle (Ve), comprising: a sensor control unit (40) that transmits sound vibrations converted from a test signal (St) from a transmitter attached to the vehicle and acquires a received signal (Sr) of the sound vibrations of the test signal measured by a receiver included in the acoustic sensor; and a signal processing unit (60) that performs processing to understand the state of the acoustic sensor based on the received signal.

2. The sound vibration detection device according to claim 1, wherein the transmitter is included in the acoustic sensor.

3. The sound vibration detection device according to claim 1, comprising: a correlation calculation unit (71) that calculates a cross-correlation function based on the received signal and the test signal or a reference signal (StE) corresponding to the test signal; and a fault detection unit (75) that detects a fault in the acoustic sensor based on the cross-correlation function.

4. The sound vibration detection device according to claim 1, comprising: a signal processing unit, a characteristic calculation unit (81) that calculates the frequency characteristics of the acoustic sensor using the received signal and the test signal or a reference signal (StE) corresponding to the test signal; and a fault detection unit (75) that detects a fault in the acoustic sensor based on the frequency characteristics of the acoustic sensor.

5. The sound vibration detection device according to claim 1, comprising: a characteristic calculation unit (81) that calculates the frequency characteristics of the acoustic sensor using the received signal and the test signal or a reference signal corresponding to the test signal; a correction value calculation unit (82) that calculates a sensor correction value based on the frequency characteristics of the acoustic sensor; and a signal correction unit (64) that corrects the received signal using the sensor correction value.

6. The sound vibration detection device according to claim 1, wherein the sensor control unit operates the sound sensor as the transmitter that transmits the sound vibration of the test signal in a test mode for performing processing to understand the state of the sound sensor, and operates the sound sensor as the receiver that receives the ambient sound in a normal measurement mode for measuring ambient sound.

7. The sound vibration detection device according to claim 6, wherein the sensor control unit operates the conversion element (21) of the acoustic sensor as the transmitter in the test mode, and operates the conversion element as the receiver in the normal measurement mode.

8. The sound vibration detection device according to claim 1, wherein the sensor control unit is electrically connected to a plurality of acoustic sensors, and in a test mode for performing processing to understand the state of the acoustic sensors, the acoustic sensor that transmits the sound vibration converted from the test signal from the transmitter and the acoustic sensor that measures the sound vibration of the test signal with the receiver are interchangeable among the plurality of acoustic sensors.

9. The sound vibration detection device according to claim 8, wherein a plurality of the acoustic sensors are attached to the same structural part and electrically connected.

10. The sound vibration detection device according to claim 5, wherein the sensor control unit is electrically connected to a plurality of acoustic sensors, and in a test mode for measuring the frequency characteristics, the acoustic sensor that transmits the sound vibration converted from the test signal from the transmitter and the acoustic sensor that measures the sound vibration of the test signal with the receiver are interchanged among the plurality, the characteristic calculation unit calculates the frequency characteristics of each acoustic sensor using the received signal and the test signal or a reference signal (StE) corresponding to the test signal, and the correction value calculation unit calculates the sensor correction value used in common to the plurality of acoustic sensors based on the frequency characteristics associated with each acoustic sensor.

11. The sound vibration detection device according to claim 3, wherein the sensor control unit is electrically connected to the acoustic sensor which includes a conversion element (21), a drive circuit (24) that operates the conversion element as the transmitter, and a receiving circuit (27) that causes the conversion element to function as the receiver, and the receiving circuit acquires the terminal voltage (Vt) of the conversion element measured by the receiving circuit during the period when the drive circuit operates the conversion element as the transmitter in accordance with the test signal as the received signal, and the fault detection unit detects a fault in the acoustic sensor based on the amplitude waveform of the received signal or the frequency characteristics of the received signal.

12. The sound vibration detection device according to claim 3, wherein the signal processing unit further includes an inverse Fourier transformer (72) that converts the cross-correlation function calculated by the correlation calculation unit into a time domain, an envelope transformer (73) that converts the cross-correlation function converted into the time domain by the inverse Fourier transformer into an envelope signal, and a maximum point detection unit (74) that detects the value and time of the maximum point occurring in the envelope signal, and the fault detection unit detects a fault in the acoustic sensor based on the value and time of the maximum point occurring in the envelope signal.

13. The sound vibration detection device according to claim 1, wherein the sensor control unit has a communication interface, the communication interface is electrically connected to a plurality of acoustic sensors via a communication bus (30), and the received signals transmitted from each of the acoustic sensors are acquired by communication.

14. The sound vibration detection device according to claim 1, wherein the sensor control unit causes the sound vibration of the test signal to be transmitted from the transmitter when the power of the vehicle is switched on, and the receiver obtains the received signal measured by the receiver, and the signal processing unit uses the received signal obtained when the power is switched on to determine the state of the acoustic sensor.

15. The sound vibration detection device according to claim 1, wherein the sensor control unit causes the sound vibration of the test signal to be transmitted from the transmitter when the vehicle's travel speed is below a threshold speed, and the receiver obtains the received signal measured by the receiver, and the signal processing unit uses the received signal obtained when the travel speed is below the threshold speed to determine the state of the acoustic sensor.

16. The sound vibration detection device according to claim 1, wherein the sensor control unit causes the sound vibration of the test signal to be transmitted from the transmitter when the engine mounted on the vehicle is stopped, and the receiver obtains the received signal measured by the receiver, and the signal processing unit uses the received signal obtained when the engine is stopped to determine the state of the acoustic sensor.

17. The sound vibration detection device according to claim 1, wherein the sensor control unit causes the sound vibration of the test signal to be transmitted from the transmitter in conjunction with an approach notification sound that notifies those around the vehicle of the vehicle's approach.

18. The sound vibration detection device according to claim 1, wherein the sensor control unit causes the acoustic sensor to continuously and periodically transmit the sound vibration of the test signal from the transmitter and measure the sound vibration of the test signal by the receiver, under predetermined conditions.

19. The sound vibration detection device according to claim 5, wherein the sensor control unit causes the sound vibration of the test signal to be transmitted from the transmitter under predetermined conditions and the receiver measures the received signal; the characteristic calculation unit calculates the frequency characteristics of the acoustic sensor using the received signal acquired under the conditions and the test signal or the reference signal; and the correction value calculation unit calculates a sensor correction value that reflects the current state of the acoustic sensor by combining a dynamic correction component calculated using the frequency characteristics and a reference initial correction component.

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