System and method for real-time acoustic monitoring of externally mounted microphones and arrays

Abstract

In at least one embodiment, a system for monitoring microphone performance in a vehicle is provided. The system includes a reference sound sensing system, a microphone, and at least one controller. The reference sound sensing system transmits a reference signal indicative of sound captured external to the vehicle. The microphone transmits a captured audio signal indicative of the sound captured external to the vehicle. The at least one controller receives the reference signal and the captured audio signal and obtains a difference between the reference signal and the captured audio signal. The at least one controller compares at least the difference to a predetermined threshold level and transmits an output signal indicative of the microphone exhibiting a performance issue.

Description

SYSTEM AND METHOD FOR REAL-TIME ACOUSTIC MONITORING OF EXTERNALLY MOUNTED MICROPHONES AND ARRAYSTECHNICAL FIELD

[0001] Aspects disclosed herein generally relate to system and method for real-time acoustic monitoring of externally mounted microphones and arrays. More specifically, aspects disclosed herein relate to system and method for performing real-time acoustic monitoring of externally mounted microphones and arrays in a vehicle. These aspects and others will be discussed in more detail below.BACKGROUND

[0002] Currently, one manner for protecting microphones entails adding mechanical protection features, such as acoustic mesh layers. These acoustic mesh layers cover the acoustic port hole of a microphone so that foreign contaminants are prevented from entering into microphone. However, this approach may not prevent the microphone performance (e.g., sensitivity, FR) from being affected due to characteristics of a microphone acoustic pathway being modified by foreign contaminant buildup. It is generally advantageous to monitor for changes in microphone performance in real time.SUMMARY

[0003] In at least one embodiment, a system for monitoring microphone performance in a vehicle is provided. The system includes a reference sound sensing system, a microphone, and at least one controller. The reference sound sensing system transmits a reference signal indicative of sound captured external to the vehicle. The microphone transmits a captured audio signal indicative of the sound captured external to the vehicle. The at least one controller receives the reference signal and the captured audio signal and obtains a difference between the reference signal and the captured audio signal. The at least one controller compares at least the difference to a predetermined threshold level and transmits an output signal indicative of the microphone exhibiting a performance issue.

[0004] In at least another embodiment, a method for monitoring microphone performance in a vehicle is provided. The method includes transmitting, via a reference sound sensing system, a reference signal indicative of sound captured external to the vehicle and transmitting, via a microphone, a captured audio signal indicative of the sound captured external to the vehicle. The method further includes receiving the reference signal and the captured audio signal and obtaining a difference between the reference signal and the captured audio signal. The method further includes comparing at least the difference to a predetermined threshold level and transmitting an output signal indicative of the microphone exhibiting a performance issue.

[0005] In at least another embodiment, a method for monitoring microphone performance in a vehicle is provided. The method includes transmitting, via a reference sound sensing system, a reference signal indicative of sound captured external to the vehicle and transmitting, via a microphone, a captured audio signal indicative of the sound captured external to the vehicle. The method further includes receiving the reference signal and the captured audio signal and obtaining a difference between the reference signal and the captured audio signal. The method further includes comparing at least the difference to a predetermined threshold level and transmitting an output signal indicative of the microphone exhibiting a performance issue.

[0006] In at least another embodiment, a computer-program product embodied in a non- transitory computer readable medium executable by at least one controller to monitor microphone performance in a vehicle is provided. The computer-program product includes instructions for transmitting, via a reference sound sensing system, a reference signal indicative of sound captured external to the vehicle and for transmitting, via a microphone, a captured audio signal indicative of the sound captured external to the vehicle. The computer-program product further includes instructions for receiving the reference signal and the captured audio signal and for obtaining a difference between the reference signal and the captured audio signal. The computer-program product further includes instructions for comparing at least the difference to a predetermined threshold level and for transmitting an output signal indicative of the microphone exhibiting a performance issue.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The embodiments of the present disclosure are pointed out with particularity in the appended claims. However, other features of the various embodiments will become more apparent and will be best understood by referring to the following detailed description in conjunction with the accompany drawings in which:

[0008] FIGURE 1 depicts measured frequency response (FR) curves of an automotive microphone tested under contaminated conditions;

[0009] FIGURE 2 depicts a panel assembly including a reference sensor mounted on a vehicle in accordance with one embodiment;

[0010] FIGURE 3 depicts FR curves for the reference sensor of the panel assembly of FIGURE 2 that are measured under similar conditions as the measured FR curves as set forth above in FIGURE 1;

[0011] FIGURE 4 depicts a system for performing real-time acoustic monitoring of microphones (or arrays) in a vehicle in accordance with one embodiment; and

[0012] FIGURE 5 depicts a method for performing real-time acoustic monitoring of microphones (or arrays) in the vehicle in accordance with one embodiment.DETAILED DESCRIPTION

[0013] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments arc merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted aslimiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0014] To detect external sound such as sirens from emergency vehicles, microphones and microphone arrays may be placed external to a vehicle. Different from interior applications, externally placed microphone modules and elements (hereafter referred to as “microphones”) are subject to harsh environmental conditions outside the vehicle, including but not limited to rain, snow, ice, hail, wind, dust, mud, oil, cleaning chemicals and so on. Sufficiently protecting microphones from environmental damage, and furthermore protecting their acoustic performance from being significantly degraded by all possible types of environmental contaminations may be a challenging task.

[0015] Traditionally, acoustic mesh layers / materials are used to cover the microphone port hole that by design is a direct air path exposing the sensing element inside the microphone to the outside sound field to be measured. Acoustic mesh is breathable to allow air (thus sound) to go through, but its pore openings are small enough to block water and dust particles whose sizes are larger than air molecules. The added acoustic mesh may be sufficient to protect a microphone element from being physically damaged by foreign contaminations, but the acoustic mesh cannot guarantee that the acoustic performance (such as the Frequency Response, or FR) of a microphone stays undisturbed under all possible environmental contamination conditions. For example, if excessive dust, ice, mud, or snow accumulates around and / or on the acoustic mesh, the acoustic path characteristics (e.g., acoustic impedance) seen by the sensing element inside the microphone housing may change compared to the original contamination-free state. This may in turn change the FR including the sensitivity of the microphone.

[0016] For external acoustic event recognition, like emergency vehicle detection (EVD) and localization, microphone arrays are commonly used. A microphone array uses the technology of acoustic beamforming that requires outputs from multiple (>=2) microphone channels, with each channel being an individual microphone with a separate port hole connected to the outside sound field. Thus, a microphone array (or array microphone) physically often appears as a device module consisting of multiple (>=2) individual microphones arranged in a certain geometrical patternwithin a housing. The microphone array detects and localizes sound by post-processing the output signals from multiple individual microphones within the array module. The post-processing (i.e., the beamforming) can be realized either by hardware circuitry, software algorithm, or a combination of both. Either way, the array hardware and / or software designs are based on, and their performance depends on, known sensitivity and FR characteristics of each individual microphone inside the array. Any unignorable sensitivity and FR changes of any microphone channels in an array will affect the detection and localization accuracy.

[0017] To give an example demonstrating the manner in which the acoustic performance of a microphone (represented by its FR) may change when a port hole of the microphone is contaminated by sand and dust. FIGURE 1 depicts experimentally measured FR curves 100a - lOOd for a typical automotive microphone that is tested under various sand and dust contamination conditions. To protect the microphone, its acoustic port hole is covered by an acoustic mesh layer (e.g., ePTFE acoustic mesh / vent from GORE®). FR curve 100a generally represents the FR of an uncontaminated (i.e., clean condition). The FR curve 100a corresponds to a default performance of the microphone. The curves 100b - lOOd on the plot represents a status of different and random amounts of sand and dust accumulation at different and random locations of the mesh layer. For example, curves 100b - lOOd generally represent the FRs under three different contamination conditions. All curves 100a - lOOd are normalized by the original (un-contaminated) microphone sensitivity at 1 kHz. It is seen that, depending on the contamination status of sand and dust, significant differences in the FRs between the un-contaminated case and the contaminated case, or between two different contaminated cases could occur in practice. Consider that if the performance for one or more microphone channels in a microphone array change from the default “un- contaminated” state (based on which the beamforming hardware / software are designed) to a random contaminated states in FIGURE 1, the array performance will be degraded. If the changes are substantial, such a condition may even result in an inoperable array. Although FIGURE 1 illustrates the FR changes of a microphone when an acoustic port of the microphone is covered (or clogged) by sand and dust, other types of contaminants commonly encountered in automotive use conditions would cause similar’ effects, including for example road dirt, mud, water, etc.

[0018] Therefore, it may be advantageous to provide a method to monitor, in real time, the performance change of a microphone, either used standalone or in an array outside of a vehicle. When acoustic performance change is detected, corresponding warnings / reminders messages should be given to the user to take proper actions, such as subsequent cleaning or repairing. Aspects as disclosed below, solve, inter alia, the issues noted herein.

[0019] In a laboratory environment, acoustic performance of a microphone or microphone array such as its overall output amplitude (e.g., which typically measured in voltage) and FR amplitude (e.g., which is its output amplitude as a function of frequency) may be measured / monitored using a calibrated sound source whose acoustic properties such as the FR are known. In another example, one mechanism may involve comparing the microphone under test with a reference microphone whose sensitivity and FR are known. This may not require a calibrated sound source. That being said, if either approach can be implemented in practice to monitor the real-time performance of the microphone mounted externally to a vehicle, this may solve one or more of the above noted problems. In general, the prevailing issue may involve how to implement a controlled sound source or a known reference microphone (or sensor) whose performance will not be noticeably affected by possible contamination conditions for automotive applications. Aspects disclosed herein y may provide an answer to one or more of these issues which generally focus on an innovative approach using, among other things, a vibration- sensing based reference sound sensing system.

[0020] FIGURE 2 depicts a panel assembly 110 including a reference sensor 116 mounted on a vehicle 112 in accordance with one embodiment. The panel assembly 110 includes a body panel 114 that may be part of a vehicle 112 for receiving the reference sensor 116. The panel assembly 110 (or the “reference sound sensing system 110”) includes the body panel 114 and the reference sensor 116. The relevance of the body panel 114 and the reference sensor 116 will be discussed in more detail below.

[0021] The reference sensor 116 may be a vibration-sensing based sensor. In one example, the reference sensor 116 may be in the form of a one-axis accelerometer that is mounted on a body structure (or the panel 114) of the vehicle 112. In one example, the panel 114 may be a bodystructure that is thin and may be externally facing body panels on the vehicle 112, such as door panel, front / rear window glass, front / rear bumper, etc.

[0022] As illustrated in FIGURE 2, when sound waves (Pin) strike on the panel 114 (e.g., door panel), vibration motions in the structure panel 114 are induced. The sound induced vibration is then picked up by the reference sensor 116 (e.g., panel-mounted accelerometer) that outputs an electrical signal (e.g., voltage) corresponding to the sound input. Effectively, the reference sensor 116 (e.g., accelerometer) together with the panel 114 on which the reference sensor 116 is mounted becomes a “microphone” (i.e., the reference sound sensing system 110). In such a case, the panel 114 is an effective structural membrane of the “microphone”. Compared to the small port hole of a classical microphone that is typically about 1 mm in diameter or less and the small sensing membrane inside the microphone element, the structural membrane (or the panel 114) as part of a vehicle body is several orders of magnitude larger in size and higher in mass. Certainly, environmental contaminants can also build up on the surface of the structure panel 114, but their influences on panel stiffness, mass and damping are basically ignorable compared to the values of the intrinsic stiffness, mass and damping of the structural panel 114 itself. Therefore, the vibration motions of the panel 114 under external sound excitation are largely unaffected by environmental contaminants.

[0023] FIGURE 3 depicts FR curves 150a - 150d (or “150”) for the reference sensor 116 of the panel assembly 110 of FIGURE 2 that are measured under similar conditions as the measured FR curves 100a - lOOd as set forth above in FIGURE 1. Again, curve 150a represents the FR under the uncontaminated (clean) condition while curves 150b - 150d are FRs measured under various contaminated conditions. It is seen that the output from the reference sensor 116 mounted on the panel 114 may be more robust given that the FR curves 150a - 150d remain primarily unchanged up to, for example, 4kHz. Comparing to FR curves 150 to the FR measurements (or curves) 100 of the microphone with the port hole as shown in FIGURE 1, the experimental observation exhibited in FIGURE 3 demonstrates the feasibility of using, for example, an accelerometer as mounted to the body panel 114 (e.g., the reference sound sensing system 110) to monitor the performance of automotive microphones in real time. In general, the FR curves 150a- 150d in FIGURE 3 demonstrate the performance stability of the reference sound sensing system 110against environmental contaminations. Since the output (i.e., overall level or FR) is stable when measured either clean or dirty (contaminated), any one or more of these curves 150a - 150d may serve as the “reference”. On the other hand, in FIGURE 1 for a classical microphone with a porthole, the performance, as illustrated in FR, varies greatly depending on the contamination status. Comparing to curve 110a which is the default FR when the microphone is clean, significant changes are observed when the microphone is dirty (e.g., contaminated curves 1 lOb-d). In general, the differences between 100b- lOOd and 100a may indicate that each case represented by curves 100b - lOOd corresponding to the microphone 120 being contaminated to the degree that a warning can be issued. However, the curves 100b - lOOd may be used as sample status. The criteria for issuing warnings due to microphone degradation will be discussed in more detail in connection with FIGURE. 4.

[0024] In practical implementations, both the reference sensor 116 and the microphones 120 whose acoustic performances are to be monitored are installed on the vehicle 112. As noted above, the reference sensor 116 as illustrated in FIGURE 2, may be, for example, a one-axis accelerometer that is preferably mounted on a thin, externally facing body panel 114 of the vehicle 112, such as door panel, front / rear window glass, front / rear bumper, etc. Although the body panel 114 may be externally facing so as to be exposed to an external sound field, the accelerometer (or reference sensor 116) may be mounted on a hidden side (i.e., B-side) of the body panel 114 for implementations where it is desirable for the reference sensor 116 to remain hidden to passengers in the vehicle 112. One example of an accelerometer that may be mounted on the body panel 114 and may be the piezoelectric diaphragm-based sound and vibration sensor disclosed in U.S. Patent No, 11,533,568 Bl which is hereby incorporated by reference in its entirety. The installation positions of the microphones 120 (or microphone arrays) to be monitored may depend on specific applications. Some typical mounting locations may include front / rear bumpers and the top of the roof where a vehicle antenna module is usually located.

[0025] Once the mounting locations of the reference sensor 116 and all of the microphones 120 on the vehicle 112 are determined, the differences in acoustic responses between the reference sensor 116 and any other microphone 120 or microphone channel (if in a microphone array) may be calibrated and established in a controlled laboratory environment. Since the “relativedifference” may be a primary parameter, the characteristics of the sound source used to establish the response differences may not be relevant. The sound source can be wide or narrow band noise (e.g., white, pink noise) or tonal sound as long as sufficient signal-to-noise ratio (SNR) is achieved to ensure reliable measurement results. Furthermore, differences in acoustic responses can be represented as the differences in the overall output levels (e.g., voltage) or in a frequency spectra. The difference in frequency spectra is expressed as a function of frequency, while the difference in overall output levels is a single-valued number that may be easier to use during the comparison process. For simplicity, the acoustic response difference as disclosed herein generally corresponds to a single-valued overall level difference. However, the disclosed system and method may be equally valid if the differences in frequency spectra are used. To some extent, comparing the spectra differences may result in more accurate monitoring performance as the frequency dependent spectrum may inherently provide more information than the single-valued overall output level.

[0026] FIGURE 4 depicts a system 200 for performing real-time acoustic monitoring of the microphone (or arrays) 120 in the vehicle 112 in accordance with one embodiment. The system includes 200 the reference sound sensing system 110 (e.g., including the body panel 114 and the reference sensor (e.g., accelerometer) 116), one or more of the microphones 120 (or microphone arrays), at least one controller 202 (“the controller 202”) and a user interface 204. It is recognized that the one or more of the microphones 120 may be implemented as various microphone channels where each microphone channel corresponds to a corresponding microphone. The controller 202 includes a plurality of filters 210a - 210b and a plurality of level comparison blocks 212a - 212n. In general, during regular operation of the vehicle 112, the microphones 120 and the reference sound sensing system 110 may constantly monitor or capture sound from external to the vehicle 112 (or environmental sound). As depicted in FIGURE 3, the acoustic performance of the reference sound sensing system 110 is stable against environmental contaminations. Thus, in this regard, the reference sensor 116 while positioned on the body panel 114 provides a reference signal to the controller 202. The reference signal may generally correspond to any one of the curves 150a - 150d as shown in FIGURE 3. Similarly, the microphones 120 positioned externally and throughout the vehicle 112 each transmit a captured audio signal to the controller 202. Each captured audio signal corresponds to an audio signal that is generated exterior (or external) to thevehicle 112. The filters 210a and 210b receive the reference signal(s) and the captured audio signal(s), respectively.

[0027] In one example, each of the filters 210a and 210b may be implemented as band pass filters. It is recognized that the filters 210a and 210b may be any type of filter. Similarly, the filters 210a and 210b may be different from one another or similar to one another. In the event the filters 210a and 210b are implemented as bandpass filters, such filters may have a low corner frequency / / and a high corner frequency ;. With reference to FIGURE 3, since the performance of the reference sensor 116 may be mostly stable against environmental contamination conditions between 100 and 4000 Hz, the low and high comer frequencies of the bandpass filters 210a and 210b may be set between 50 and 500 Hz and between 3000 and 5000 Hz, respectively. These aspects are generally indicative of the advantages provided by bandpass filtering the microphone inputs. In general, the reference signal provided by the reference sensor 116 generally corresponds to the sound pressure level as measured by the reference sensor 116 mounted on the panel 11 .

[0028] The filter 210a provides a filtered reference signal (e.g., an overall level expressed as, for example, a single-valued number Lref) to the various level comparison blocks 212a - 212n. Similarly, the filter 210b provides a filtered captured audio signal (e.g., overall levels Lmic_i - LmiC_n, each expressed, for example, as a single- valued number) to each of the level comparison blocks 212a - 212n. In general, the total number of level comparison blocks 212 implemented with the controller 202 may depend on the number of microphones 120 implemented on the vehicle 112. The filtered reference signal (e.g., Lref) may have a FR that is similar to the curve 150a as shown in connection with FIGURE 3, which represents the default acoustic response of the reference sound sensing system 110 measured under the uncontaminated condition. It is recognized that any curves 150b - 150d can also represent the default acoustic response of the reference sound sensing system 110 within the frequency band between and ; since such curves 150b - 150d overlap with curve 150a. In this regard, any one of the curves 150a - 150d may be considered predetermined FR curves since such curves have been ascertained through vehicle level testing during initial configuration setups prior to the vehicle 102 being produced by the vehicle OEM.

[0029] The level comparison block 212a compares the filtered reference signal (e.g., Lref) to a first filtered captured audio signal (e.g., LmiC_i). Similarly, the level comparison block 212b compares the filtered reference signal (e.g., Lref) to a second filtered captured audio signal (e.g., Lmic_2) and any remaining level comparison blocks 212n compares the filtered reference signal (e.g., Lref to remaining filtered captured audio signals (e.g., Lmic_n). In general, the sound pressure level measured by the reference sensor 116 is stable regardless of the environmental contamination conditions, while the output level or captured audio signal from the microphone 120 could change significantly depending on the manner in which a port hole of the microphone 120 is being affected by environmental contaminations.

[0030] Each level comparison block 212 determine whether a corresponding microphone 120 is contaminated to the point where the reading provided from such a microphone 120 is no longer deemed valid based on the following equation:

[0031] \Lref- Lmie_ jv| > LAN + s) (Eq. 1)

[0032] In short, each level comparison block 212 in the controller 202 takes a difference of the filtered reference signal Lref) and the filtered captured audio signal (Lracjv) and a corresponding absolute value and compares this value to a predetermined value that is based on a predetermined- calibration level (e.g., LAN) in addition to a tolerance value, 5 (e.g., collectively the predetermined calibration level and the tolerance value may be defined as a predetermined threshold level). Therefore, if the absolute level difference \Lrej^LmicN\ is larger than the pre-calibrated level difference L N plus the tolerance value 5 (or the predetermined threshold level), the controller 202 determines that the acoustic performance for the corresponding microphone 120 has changed due to environmental contamination conditions or other possible causes. In this case, when the microphone 120 that has exhibited such a change with its environmental contamination, the controller 202 determines that this particular microphone 120 is generally inoperable and transmits an output signal to the user interface 204. The user interface 204 notifies the driver and / or occupant in the vehicle 112 of the faulty microphone 120. In this regal’d, the user interface 204 may generate any one or more of an audio warning, a visual warning (e.g., light emitting diode(LED) is activated), or an error code that is stored in the controller 202 that may be retrieved via a diagnostic tool.

[0033] With the above comparison as noted above in connection with Eq. 1, the tolerance value, 5 is generally related to a robustness requirement of the specific application to the microphone performance change. In general, 5 (or the tolerance value) may be a value that is anywhere between 1 and lOdB. The pre-calibrated level difference LAV represents a difference between a response of the reference sound sensing system 110 and the default response of the N'hmicrophone measured under its original uncontaminated condition. The pre-calibrated level difference L V may be determined through testing during the design stage.

[0034] FIGURE 5 depicts a method 250 for performing real-time acoustic monitoring of microphones (or arrays) 120 in the vehicle 112 in accordance with one embodiment.

[0035] In operation 252, the controller 202 receives a signal indicating that the vehicle 112 has been started and the vehicle 112 is operational (e.g., ignition is in “RUN”). In this instance, the controller 202 initiates the process of monitoring, in real time, whether any one or more of the microphones 120 are contaminated.

[0036] In operation 254, the reference sensor 116 generates the reference signal in response to an external sound being generated from outside of the vehicle 112. The reference signal generally corresponds to a measured sound pressure while the reference sensor 116 is positioned on the body panel 114 as noted above. The reference sensor 116 transmits the reference signal to the controller 202. Each microphone 120 (or microphone array 120) positioned in the vehicle 112 also captures the external sound at the same time and transmits a captured audio signal to the controller 202. It is recognized that the external sound can be any sound in the surrounding environment of the vehicle 112 during operation of the reference sound sensing system 110, including traffic sounds, siren sounds, vehicle horn sounds, etc. However, in one example, the real-time acoustic performance monitoring of microphones (or arrays) 120 may only occur during loud external sound events, for example siren sound events or vehicle horn sound events. This aspect is discussed in connection with operation 258.

[0037] In operation 256, the filter 210a receives the reference signal from the reference sensor 116. As noted above, the filter 210a may be implemented as a bandpass filter as such filters may have a low corner frequency / and a high corner frequency / ,. Given that the performance of the reference sensor 116 may be mostly stable against environmental contamination conditions between 100 and 4000 Hz, the low and high comer frequencies of the bandpass filters 210a and 210b may be set between 50 and 500 Hz (e.g., on the low frequency end) and between 3000 and 5000 Hz (e.g., on the high frequency end), respectively. The filter 210a provides the filtered reference signal (e.g., Lref) to the various level comparison blocks 212a - 212n.

[0038] In operation 258, the controller 202 compares the filtered reference signal (e.g., Lref) to a predetermined reference threshold (e.g., Lth). This operation may be optionally performed by the controller 202. The controller 202 compares the filtered reference signal (e.g., Lref) to the predetermined reference threshold (e.g., Lth) to ensure that the sound (or sound pressure) that is being detected by the reference sensor 116 exceeds a predetermined sound level, fdtered reference signal (e.g., Lref) is greater than the predetermined reference threshold (e.g., Lth), the method 250 moves to operation 260. If not, then the method 250 moves back to operation 254. The operation 258 may be optional and ensures that the microphone performance monitoring only occur when there are loud sound events, thus sufficient measurement signal to noise ratio (SNR) to improve the reliability of the monitoring process as well as minimize false alarms.

[0039] In operation 260, the filter 210b receives the captured audio signal(s) from the microphones 120. As noted above, the filter 210b may be implemented as a bandpass filter as such filters may have a low corner frequency / and a high comer frequency / ,. As each filtered microphone output resulting from the filter 210b will be subsequently compared with the filtered reference sensor output from filter 210a, the low and high comer frequencies of the bandpass filters 210a and 210b may be set similarly between 50 and 500 Hz (e.g., on the low frequency end) and between 3000 and 5000 Hz (e.g., on the high frequency end), respectively. The filter 210b provides the filtered captured audio signal (e.g., LmiC_i - LmiC-n) to each of the level comparison blocks 212a - 212n. In general, the low and high corner frequencies are set based on the performance of the reference sensor 116 mounted on the panel 114 (e.g., the reference sound sensing system 110) which may be most stable between 100 and 4000 Hz as shown in Fig. 3. Theoutput of the microphone 120 under monitoring should pass through the same filter with similar settings to ensure signals within the same frequency band are compared. Since the reference sensor signal is stable regardless of the environmental condition, when comparing the microphone output with the reference sensor output, a significant change from the predetermined threshold level (see Eq. 1) indicates changes with the microphone under monitoring.

[0040] In operation 262, the filter 210a provides the filtered reference signal (e.g., Lref) to the various level comparison blocks 212a - 212n. Similarly, the filter 210b provides the filtered captured audio signal (e.g., Lmic_i - L,„ic_n) to each of the level comparison blocks 212a - 212n. Each of the level comparison blocks 212a - 212n execute equation 1 as noted above (e.g., \Lrej^Lmic_N\ > (L / \N+S)) to determine any one or more of the microphones 120 are exhibiting a contamination issue that affects the functionality of the microphone 120. If the absolute value of the difference between the filtered reference signal and the filtered captured audio signal is greater than the predetermined threshold level, then the method 250 moves to operation 264. If the absolute value of the difference between the filtered reference signal and the filtered captured audio signal is less than the predetermined threshold level, then the method 250 moves back to operation 254. In this case, the microphone 120 is considered to be operating properly and does not exhibit contamination that effects the functionality of the microphone 120.

[0041] In operation 266, the controller 202 transmits an output signal to the user interface 204 to indicate that one or more the microphone 120 are not functioning properly or that the microphone 120 is exhibiting a performance issue.

[0042] It is recognized that the controllers as disclosed herein may include various microprocessors, integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof), and software which co-act with one another to perform operation(s) disclosed herein. In addition, such controller(s) as disclosed utilizes one or more microprocessors to execute a computer-program that is embodied in a non-transitory computer readable medium that is programmed to perform any number of the functions as disclosed. Further, the controller(s) asprovided herein includes a housing and the various number of microprocessors, integrated circuits, and memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM)) positioned within the housing. The controller(s) as disclosed also include hardware-based inputs and outputs for receiving and transmitting data, respectively from and to other hardware-based devices as discussed herein.

[0043] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.

Claims

WHAT IS CLAIMED IS:

1. A system for monitoring microphone performance in a vehicle, the system comprising: a reference sound sensing system configured to transmit a reference signal indicative of sound captured external to the vehicle; a microphone configured to transmit a captured audio signal indicative of the sound captured external to the vehicle; and at least one controller programmed to: receive the reference signal and the captured audio signal; obtain a difference between the reference signal and the captured audio signal; compare at least the difference to a predetermined threshold level; and transmit an output signal indicative of the microphone exhibiting a performance issue.

2. The system of claim 1, wherein the reference sound sensing system includes: a body panel positioned in the vehicle; and a reference sensor being configured to transmit the reference signal while the reference sensor is positioned on the body panel.

3. The system of claim 2, wherein the reference signal corresponds to a measured sound pressure related to the sound captured external to the vehicle.

4. The system of claim 2, wherein the reference signal generally corresponds to a predetermined frequency response curve.

5. The system of claim 1, wherein the at least one controller includes at least one filter programmed to filter the reference signal and the captured audio signal prior to obtaining the difference.

6. The system of claim 5, wherein the at least one filter is programmed to filter the reference signal and the captured audio signal within a predetermined frequency range.

7. The system of claim 5, wherein the at least one filter is a bandpass filter.

8. The system of claim 1, wherein the at least one controller is further programmed to obtain an absolute value of the difference between the reference signal and the captured audio signal prior to comparing the at least the difference to a predetermined threshold level.

9. The system of claim 1, wherein the at least one controller is further programmed to transmit the output signal in response to the at least the difference exceeding the predetermined threshold level.

10. A method for monitoring microphone performance in a vehicle, the method comprising: transmitting, via a reference sound sensing system, a reference signal indicative of sound captured external to the vehicle; transmitting, via a microphone, a captured audio signal indicative of the sound captured external to the vehicle; and receiving the reference signal and the captured audio signal; obtaining a difference between the reference signal and the captured audio signal; comparing at least the difference to a predetermined threshold level; and transmitting an output signal indicative of the microphone exhibiting a performance issue.

11. The method of claim 10 further comprising transmitting, via a reference sensor positioned on a body panel, the reference signal.

12. The method of claim 11, wherein the reference signal corresponds to a measured sound pressure related to the sound captured external to the vehicle.

13. The method of claim 11, wherein the reference signal generally corresponds to a predetermined frequency response curve.

14. The method of claim 11 further comprising filtering the reference signal and the captured audio signal prior to obtaining the difference.

15. The method of claim 14, wherein the filtering of the reference signal and the captured audio signal further includes filtering the reference signal and the captured audio signal within a predetermined frequency range.

16. The method of claim 11 further comprising obtaining an absolute value of the difference between the reference signal and the captured audio signal prior to comparing the at least the difference to a predetermined threshold level.

17. The method of claim 11 further comprising transmitting the output signal in response to the at least the difference exceeding the predetermined threshold level.

18. A computer-program product embodied in a non- transitory computer readable medium executable by at least one controller to monitor microphone performance in a vehicle, the computer-program product comprising instructions for: receiving a reference signal indicative of sound captured external to the vehicle; receiving a captured audio signal indicative of the sound captured external to the vehicle; and obtaining a difference between the reference signal and the captured audio signal; comparing at least the difference to a predetermined threshold level; and transmitting an output signal indicative of the microphone exhibiting a performance issue.

19. The computer-program product of claim 18 further comprising instructions for filtering the reference signal and the captured audio signal prior to obtaining the difference.

20. The computer- program product of claim 19 further comprising instructions for filtering the reference signal and the captured audio signal within a predetermined frequency range.

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