Patent Description:
Current vehicle cabin acoustics predicate that any sound that occurs in the cabin will generally be perceived as one noisy stimulus. Common examples of interference sources include road noise, wind noise, passenger speech, and multimedia content. The presence of these noise sources complicates speech perception by reducing speech intelligibility, signal-to noise ratio, and subjective call quality. Many modern techniques exist to improve the telecommunications experience for the near-end participants (i.e., driver or other occupants of the source vehicle), but thus far nothing has attempted to improve call quality for the far-end participants of telecommunication.

Document <CIT> discloses an active noise cancellation system for an aircraft In-flight entertainment system including at least one input device, a processing means, and an output. The input device may be associated with a seat on the aircraft and adapted to receive an input representative of an ambient noise in the vicinity of the seat. The processing means may be adapted to process the input to produce an output signal adapted to reduce the ambient noise in volume associated with the seat. The output may be adapted to transmit an output signal to at least one driver, which is adapted to transmit the output signal to a user.

Document <CIT> discloses a method for adjusting a listening area of a microphone, the method including detecting an initial listening zone; capturing a captured sound through a microphone array; identifying an initial sound based on the captured sound and the initial listening zone wherein the initial sound includes sounds within the initial listening zone; adjusting the initial listening zone and forming the adjusted listening zone; and identifying an adjusted sound based on the captured sound and the adjusted listening zone wherein the adjusted sound includes sounds within the adjusted listening zone.

Document <CIT> discloses a system for discerning an audible command from ambient noise in a vehicular cabin. The system comprises a microphone array and a signal processing system.

Document <CIT> discloses a system for detecting noise in a signal received by a microphone array. The system provides for the reduction of noise in a signal received by a microphone array. The signal to noise ratio in handsfree systems may be improved, particularly in handsfree systems present in a vehicular environment.

Document <CIT> discloses a system having microphone devices with a clock generator outputting a digital signal, where the microphone devices are connected with a data transfer network. A CPU comprises a clock generator, and is communicatively coupled with the network. An algorithm is executable by the CPU for computation of a directional microphone. The network is formed as a digital car bus system, which transfers the signal from the microphone devices to the CPU. Each microphone device or the CPU comprises a synchronizer e.g. master clock, for clock synchronization of the generator. The directional microphone is designed as a microelectromechanical system (MEMS) microphone. The bus system is used as a Media Oriented Systems Transport (RTM: high-speed multimedia network) bus system or a FlexRay (RTM: digital serial bus system) bus system.

Document <CIT> discloses a microphone mounting assembly that includes one or more transducers mounted to a printed circuit board (PCB) where a spacer is used having a channel positioned on the PCB for allowing acoustical energy to pass through the channel to a port in the PCB. A first cover is positioned over the channel for disrupting the direct encounter with airflow into the channel while a top section having a second cover is further positioned adjacent to the first fabric cover for preventing debris from obstructing the first fabric cover.

Document <CIT> discloses a rearview assembly that includes a housing for attaching to the vehicle, the housing defining an interior space that is acoustically separated into at least two chambers; a first speaker that is located in a first one of the at least two chambers of the interior space of the housing; a first microphone subassembly located on the top surface of the housing; a second microphone subassembly located on the bottom surface of the housing; a display positioned in the housing; an audio/data transceiver for transmitting and receiving audio and data signals to/from a portable device; and a control circuit for determining whether a portable device having a predetermined identification code is within the range of the audio/data transceiver, and for exchanging data with the portable device through the audio/data transceiver.

The problem underlying the present application is solved by a noise cancellation system having the features of claim <NUM>.

A system of one or more computers can be configured to perform particular operations or actions by virtue of having software, firmware, hardware, or a combination of them installed on the system that in operation causes or cause the system to perform the actions. One or more computer programs can be configured to perform particular operations or actions by virtue of including instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions. One general aspect includes a noise cancellation system according to claim <NUM>.

Implementations may include one or more of the following features. The microphones may be positioned within the first listening zone, and the digital signal processor may be further programmed to suppress sound received from the second listening zone. The second listening zone may be rearward of the first listening zone. The microphones may be omnidirectional. The microphones may be located on an inboard side surface of the first headrest. Alternatively, the microphones may be located on a bottom surface of the first headrest. The two microphones may be further separated in a lateral direction with respect to the vehicle, and the first listening zone may include two listening subzones oriented in the lateral direction relative to each other. The digital signal processor may be further programmed to suppress sound received from one of the listening subzones. The noise cancellation system may further include a second microphone array having at least two microphones. The microphones in the second microphone array may be mounted to a bottom surface of a second headrest laterally adjacent to the first headrest. The two microphones in the second headrest may be spaced apart in both the longitudinal direction and the lateral direction.

The noise cancellation system may further include a second microphone array having at least two microphones mounted in a rearview mirror assembly. The at least two microphones in the second microphone array may be spaced apart in a lateral direction with respect to the vehicle. The at least two microphones in the rearview mirror assembly may be directional microphones such that the first listening zone includes two listening subzones oriented in the lateral direction with respect to the vehicle. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium.

Any one or more of the controllers or devices described herein include computer executable instructions that may be compiled or interpreted from computer programs created using a variety of programming languages and/or technologies. In general, a processor (such as a microprocessor) receives instructions, for example from a memory, a computer-readable medium, or the like, and executes the instructions. A processing unit includes a non-transitory computer-readable storage medium capable of executing instructions of a software program. The computer readable storage medium may be, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semi-conductor storage device, or any suitable combination thereof.

The present disclosure describes an in-vehicle noise-cancellation system for optimizing far-end user experience. The noise-cancellation system may improve the intelligibility of near-end speech at the far-end of a communications exchange, including a telecommunications exchange or dialogue with a virtual personal assistant, or the like. The noise-cancellation system may incorporate real-time acoustic input from the vehicle, as well microphones from a telecommunications device. Moreover, audio signals from small, embedded microphones mounted in the car can be processed and mixed into an outgoing telecommunications signal to effectively cancel acoustic energy from one or more unwanted sources in the vehicle. Audio playing from a known audio stream (e.g., music, sound effects, and dialog from a film audio) in the vehicle's infotainment system, in addition to unwanted noise (e.g., children yelling and background conversations) captured by the embedded microphones, may be used as direct inputs to the noise-cancellation system. As direct inputs, these streams can, therefore, be cancelled from the outgoing telecommunications signal, thus providing the user's far-end correspondent with much higher signal-to-noise ratio, call quality, and speech intelligibility.

<FIG> illustrates a telecommunications network <NUM> for facilitating a telecommunications exchange between a near-end participant <NUM> in a vehicle <NUM> and a remote, far-end participant <NUM> located outside the vehicle via a cellular base station <NUM>. The vehicle <NUM> may include a telecommunications system <NUM> for processing incoming and outgoing telecommunications signals, collectively shown as telecommunications signals <NUM> in <FIG>. The telecommunications system <NUM> may include a digital signal processor (DSP) <NUM> for processing audio telecommunications signals, as will be described in greater detail below. The DSP <NUM> may be a separate module from the telecommunications system <NUM>. A vehicle infotainment system <NUM> may be connected to the telecommunications system <NUM>. A first transducer <NUM> or speaker may transmit the incoming telecommunications signal to the near-end participant of a telecommunications exchange inside a vehicle cabin <NUM>. Accordingly, the first transducer <NUM> may be located adjacent to a near-end participant or may generate a sound field localized at a particular seat location occupied by the near-end participant. A second transducer <NUM> may transmit audio from the vehicle's infotainment system <NUM> (e.g., music, sound effects, and dialog from a film audio).

A first microphone array <NUM> may be located in the vehicle cabin <NUM> to receive speech of the near-end participant (i.e., driver or another occupant of the source vehicle) in a telecommunication. A second microphone array <NUM> may be located in the vehicle cabin <NUM> to detect unwanted audio sources (e.g., road noise, wind noise, background speech, and multimedia content), collectively referred to as noise. Collectively, the telecommunications system <NUM>, the DSP <NUM>, the infotainment system <NUM>, the transducers <NUM>, <NUM>, and the microphone arrays <NUM>, <NUM> may form an in-cabin noise cancellation system <NUM> for far-end telecommunications.

<FIG> is a block diagram of the noise cancellation system <NUM> depicted in <FIG>. As show in <FIG>, an incoming telecommunications signal 112a from a far-end participant (not shown) may be received by the DSP <NUM>. The DSP <NUM> may be a hardware-based device, such as a specialized microprocessor and/or combination of integrated circuits optimized for the operational needs of digital signal processing, which may be specific to the audio application disclosed herein. The incoming telecommunications signal 112a may undergo automatic gain control at an automatic gain controller (AGC) <NUM>. The AGC <NUM> may provide a controlled signal amplitude at its output, despite variation of the amplitude in the input signal. The average or peak output signal level is used to dynamically adjust the input-to-output gain to a suitable value, enabling the circuit to work satisfactorily with a greater range of input signal levels. The output from the AGC <NUM> may then be received by a loss controller <NUM> to undergo loss control, which is then passed to an equalizer <NUM> to equalize the incoming telecommunications signal 112a. Equalization is the process of adjusting the balance between frequency components within an electronic signal. Equalizers strengthen (boost) or weaken (cut) the energy of specific frequency bands or "frequency ranges.

The output of the equalizer <NUM> may be received by a limiter <NUM>. A limiter is a circuit that allows signals below a specified input power or level to pass unaffected while attenuating the peaks of stronger signals that exceed this threshold. Limiting is a type of dynamic range compression; it is any process by which a specified characteristic (usually amplitude) of the output of a device is prevented from exceeding a predetermined value. Limiters are common as a safety device in live sound and broadcast applications to prevent sudden volume peaks from occurring. A digitally processed incoming telecommunications signal 112a' may then be received by the first transducer <NUM> for audible transmission to the near-end participant of the telecommunications exchange.

As also shown in <FIG>, noise cancellation system <NUM> may include the first microphone array <NUM> and the second microphone array <NUM>. The first microphone array <NUM> may include a plurality of small, embedded microphones strategically located in the vehicle cabin to receive speech from a near-end participant (i.e., driver or another occupant of the source vehicle) of the telecommunications exchange. According to the invention, the first microphone array <NUM> is mounted to a headrest as shown in <FIG>. The second microphone array <NUM> may include a plurality of small, embedded microphones strategically located in the vehicle cabin to detect unwanted audio sources (e.g., road noise, wind noise, background speech, and multimedia content), collectively referred to as noise.

Both inputs to the first and second microphone arrays, near-end speech and noise, respectively, may be processed using the DSP <NUM>. A set of first audio signals <NUM> (i.e., indicative of the near-end speech) from the first microphone array <NUM> may be fed into a first beamformer <NUM> for beamforming, while a set of second audio signals <NUM> (i.e., indicative of noise) may be fed into a second beamformer <NUM>. Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an array in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Beamforming can be used at both the transmitting and receiving ends to achieve spatial selectivity. The improvement compared with omnidirectional reception/transmission is known as the directivity of the array. To change the directionality of the array when transmitting, a beamformer controls the phase and relative amplitude of the signal at each transmitter, to create a pattern of constructive and destructive interference in the wavefront. When receiving, information from different sensors is combined in a way where the expected pattern of radiation is preferentially observed.

The first beamformer <NUM> may output a near-end speech signal <NUM> indicative of the near-end speech detected by the first microphone array <NUM>. Alternatively, the near-end speech signal <NUM> may be received by the DSP <NUM> directly from the first microphone array <NUM> or an individual microphone in the first microphone array. The second beamformer <NUM> may output a noise signal <NUM> indicative of the unpredictable, background noise detected by the second microphone array <NUM>. Alternatively, the noise signal <NUM> may be received by the DSP <NUM> directly from the second microphone array <NUM> or an individual microphone in the second microphone array.

The near-end speech signal <NUM> may be received by an echo canceller <NUM> along with the digitally processed incoming telecommunications signal 112a' from the far-end participant <NUM>. Echo cancellation is a method in telephony to improve voice quality by removing echo after it is already present. In addition to improving subjective quality, this process increases the capacity achieved through silence suppression by preventing echo from traveling across a network. There are various types and causes of echo with unique characteristics, including acoustic echo (sounds from a loudspeaker being reflected and recorded by a microphone, which can vary substantially over time) and line echo (electrical impulses caused by, e.g., coupling between the sending and receiving wires, impedance mismatches, electrical reflections, etc., which varies much less than acoustic echo). In practice, however, the same techniques are used to treat all types of echo, so an acoustic echo canceller can cancel line echo as well as acoustic echo. Echo cancellation involves first recognizing the originally transmitted signal that re-appears, with some delay, in the transmitted or received signal. Once the echo is recognized, it can be removed by subtracting it from the transmitted or received signal. Though this technique is generally implemented digitally using a digital signal processor or software, although it can be implemented in analog circuits as well.

The output of the echo canceller <NUM> may be mixed with the noise signal <NUM> (i.e., unpredictable noise) from the second beamformer <NUM> and an infotainment audio signal <NUM> (i.e., predictable noise) from the infotainment system <NUM> at a noise suppressor <NUM>. Mixing the near-end speech signal <NUM> with the noise signal <NUM> and/or the infotainment audio signal <NUM> at the noise suppressor <NUM> can effectively cancel acoustic energy from one or more unwanted sources in the vehicle <NUM>. The audio playing from a known audio stream (e.g., music, sound effects, and dialog from a film audio) in the vehicle's infotainment system <NUM> may be considered predictable noise and may be used as a direct input to the noise-cancellation system <NUM> and cancelled or suppressed from the near-end speech signal <NUM>. Moreover, additional unwanted and unpredictable noise (e.g., children yelling and background conversations) captured by the embedded microphones may also be used as direct inputs to the noise-cancellation system <NUM>. The unwanted noise may be cancelled or suppressed from the near-end speech signal <NUM> by the noise suppressor <NUM> based on the noise signal <NUM> and the infotainment audio signal <NUM> before being communicated to the far-end participant as an outgoing telecommunications signal 112b. Noise suppression is an audio preprocessor that removes background noise from the captured signal.

A noise-suppressed, near-end speech signal <NUM>' may be output from the noise suppressor <NUM> and may be mixed with the processed incoming telecommunications signal 112a' from the far-end participant at an echo suppressor <NUM>. Echo suppression, like echo cancellation, is a method in telephony to improve voice quality by preventing echo from being created or removing it after it is already present. Echo suppressors work by detecting a voice signal going in one direction on a circuit, and then inserting a great deal of loss in the other direction. Usually the echo suppressor at the far-end of the circuit adds this loss when it detects voice coming from the near-end of the circuit. This added loss prevents the speaker from hearing their own voice.

The output from the echo suppressor <NUM> may then undergo automatic gain control at an automatic gain controller (AGC) <NUM>. The AGC <NUM> may provide a controlled signal amplitude at its output, despite variation of the amplitude in the input signal. The average or peak output signal level is used to dynamically adjust the input-to-output gain to a suitable value, enabling the circuit to work satisfactorily with a greater range of input signal levels. The output from the AGC <NUM> may then be received by an equalizer <NUM> to equalize the near-end speech signal. Equalization is the process of adjusting the balance between frequency components within an electronic signal. Equalizers strengthen (boost) or weaken (cut) the energy of specific frequency bands or "frequency ranges.

The output from the equalizer <NUM> may be sent to a loss controller <NUM> to undergo loss control. The output may then be passed through a comfort noise generator (CNG) <NUM>. CNG <NUM> is a module that inserts comfort noise during periods that there is no signal received. CNG may be used in association with discontinuous transmission (DTX). DTX means that a transmitter is switched off during silent periods. Therefore, the background acoustic noise abruptly disappears at the receiving end (e.g. far-end). This can be very annoying for the receiving party (e.g., the far-end participant). The receiving party might even think that the line is dead if the silent period is rather long. To overcome these problems, "comfort noise" may be generated at the receiving end (i.e., far-end) whenever the transmission is switched off. The comfort noise is generated by a CNG. If the comfort noise is well matched to that of the transmitted background acoustic noise during speech periods, the gaps between speech periods can be filled in such a way that the receiving party does not notice the switching during the conversation. Since the noise constantly changes, the comfort noise generator <NUM> may be updated regularly.

The output from the CNG <NUM> may then be transmitted by the telecommunications system to the far-end participant of the telecommunications exchange as the outgoing telecommunications signal 112b. By cancelling noise inputs directly from the outgoing telecommunications signal, a user's far-end correspondent may be provided with much higher signal-to-noise ratio, call quality, and speech intelligibility.

Although shown and described as improving near-end speech intelligibility at a far-end participant of a telecommunications exchange, the noise-cancellation system <NUM> may be employed to improve near-end speech intelligibility at a far-end of any communications exchange. For instance, the noise-cancellation system <NUM> may be used in connection with virtual personal assistance (VPA) applications to optimize speech recognition at the far-end (i.e., a virtual personal assistant). Accordingly, background (unwanted) noise may be similarly suppressed or canceled from the near-end speech of a communications exchange with the VPA.

<FIG> is a simplified, exemplary flow diagram depicting a noise cancellation method <NUM> for far-end telecommunications. At step <NUM>, near-end speech may be received at the noise cancellation system <NUM> by a microphone array, such as the first microphone array <NUM>. Meanwhile, the noise cancellation system <NUM> may receive audio input streams from unwanted sources, such as unpredictable noise from the second microphone array <NUM> and/or predictable noise from the infotainment system <NUM>, as provided at step <NUM>. The near-end speech may be processed into an outgoing telecommunications signal 112b for receipt by a far-end participant of a telecommunications exchange. Accordingly, at step <NUM>, the near-end speech signal may undergo an echo cancelling operation to improve voice quality by removing echo after it is already present. As previously described, echo cancellation involves first recognizing the originally transmitted signal that re-appears, with some delay, in the transmitted or received signal. Once the echo is recognized, it can be removed by subtracting it from the transmitted or received signal.

The near-end speech signal may be received at a noise suppressor along with the noise inputs received at step <NUM> and an incoming telecommunications signal for the far-end participant (step <NUM>). During noise cancelling, the noise may be cancelled or suppressed from the near-end speech signal, as provided at step <NUM>. At step <NUM>, intelligibility of the speech in the near-end speech signal may be restored by reducing or cancelling the effects of masking by extraneous sounds. The near-end speech signal may then undergo echo suppression using the incoming telecommunications signal, as provided at step <NUM>. As previously described, echo suppression, like echo cancellation, is a method in telephony to improve voice quality by preventing echo from being created or removing it after it is already present. The near-end speech signal may undergo additional audio filtering at step <NUM> before it is transmitted to the far-end participant (step <NUM>) via the telecommunications network as an outgoing telecommunications signal. Meanwhile, the incoming telecommunications signal may be played in the vehicle cabin through speakers (step <NUM>).

<FIG> illustrates an exemplary microphone placement within the cabin <NUM> of the vehicle <NUM>, according to one or more embodiments of the present disclosure. According to the invention, a first microphone 124a, from the first microphone array <NUM>, for picking up near-end speech is embedded in one or more headrests <NUM>. A second microphone 126a, from the second microphone array <NUM>, for picking up noise may also be embedded in one or more headrests <NUM>, a headliner (not shown), or the like. As shown, microphones positioned toward the inside of passengers with respect to the vehicle cabin <NUM>, as near a user's mouth as possible, may minimize the reflective energy in the signal, as compared to microphones positioned to the outside of passengers with respect to the vehicle cabin. This is because microphones positioned to the outside of passengers with respect to the vehicle cabin may receive more reflective energy from reflective surfaces <NUM>, such as glass, enclosing the vehicle cabin <NUM>. Minimizing the reflective energy in the near-end speech signal may increase speech intelligibility at the far-end of a telecommunication. The placement and/or location of the microphones shown in <FIG> is an example only. The exact location of the microphone arrays will depend on boundaries and coverage area inside a vehicle.

<FIG> illustrates an exemplary set-up for a headrest-based telecommunications system for a vehicle. A first, forward-facing microphone array <NUM> may be placed near a front <NUM> of a front passenger headrest <NUM> for receiving near-end speech of a telecommunications exchange. A second, rearward-facing microphone array <NUM> may be placed near a back <NUM> of the front passenger headrest <NUM> for receiving noise, including background speech. <FIG> illustrates another exemplary set-up for a headrest-based telecommunications system for a vehicle. A first, forward-facing microphone array <NUM> may be placed near a front <NUM> of a front passenger headrest <NUM> for receiving near-end speech of a telecommunications exchange. A second, forward-facing microphone array <NUM> may be placed near a front <NUM> of a rear passenger headrest <NUM> for receiving noise, including background speech. As with <FIG>, the exact location of the microphone arrays illustrated in <FIG> will depend on boundaries and coverage area inside a vehicle.

<FIG> depict various plan views of sample microphone configurations for the noise cancellation system <NUM> (not shown) within the cabin <NUM> of a vehicle, such as vehicle <NUM>. As with the microphones and microphone arrays described in connection with <FIG> and <FIG>, the various microphone arrays and/or individual microphones shown in <FIG> may be in communication with the digital signal processor <NUM> to work in connection with a vehicle communications system, such as an in-car communications system or telecommunications system <NUM>. For example, <FIG> is a plan view of the vehicle <NUM> depicting a first sample microphone configuration, in accordance with one or more embodiments of the present disclosure. As shown, the noise cancellation system <NUM> (not shown) includes at least one microphone array <NUM> including at least two microphones - a first microphone 710a and a second microphone 710b. The first and second microphones may be mounted to an external surface <NUM> of a first headrest <NUM> at spaced-apart locations. The first headrest <NUM> may be a driver's side headrest.

The external surface <NUM> of the first headrest <NUM> may include an inboard side surface <NUM> and an outboard side surface <NUM>. The inboard side surface <NUM> may be nearer a center of the vehicle cabin <NUM> than the outboard side surface <NUM>, which is nearer a side of the vehicle <NUM>, including reflective surfaces <NUM> (see <FIG>). As shown in <FIG>, the first and second microphones 710a,b may be positioned flush on the inboard side surface <NUM> of the first headrest <NUM>. The first and second microphones 710a,b may be spaced apart in at least a longitudinal direction with respect to the vehicle <NUM>. Thus, a distance separating the first and second microphones includes at least a longitudinal distance X to create at least a first listening zone <NUM> and a second listening zone <NUM> oriented in the longitudinal direction. The longitudinal distance X between the two microphones in the microphone array <NUM> may give an indication of the direction of incoming sound, generally front or back. Accordingly, the first listening zone <NUM> may comprise a forward region of the passenger cabin <NUM>, such as a region encompassing a front seating row, while the second listening zone <NUM> may comprise a region that is oriented rearward of the first listening zone <NUM>, such as a region encompassing a rear passenger seat. In an embodiment, the longitudinal distance X between the first and second microphones 710a,b may be approximately one inch, though other distances between the microphones may be employed to give an indication of the direction of incoming sound, forward or rearward.

The digital signal processor <NUM> is programmed to receive microphone signals indicative of sound from the microphone array <NUM>, as shown in <FIG>, and identify whether the sound is received from a direction of the first listening zone <NUM> or the second listening zone <NUM> based on the microphone signals. According to the invention, the digital signal processor <NUM> compares the microphone signals from the first and second microphones 710a,b and localizes the direction of the sound from either the first listening zone or the second listening zones based on a time difference of arrival of the microphone signals at each of the two microphones. Moreover, the digital signal processor <NUM> suppresses or cancels the microphone signals indicative of sound from (the direction of) the second listening zone <NUM>, which may be equated with unwanted or disturbing background noise. On the other hand, the digital signal processor <NUM> transmits microphone signals indicative of sound from (the direction of) the first listening zone <NUM>, which may be equated with wanted, near-end speech, to a far-end participant in a communications exchange.

According to an embodiment, the first and second microphones 710a,b may be omnidirectional microphones. According to another embodiment, the first and second microphones 710a,b may be directional microphones having a directivity in the direction of the corresponding listening zones.

<FIG> is a plan view of the vehicle <NUM> depicting another sample microphone configuration, in accordance with one or more embodiments of the present disclosure. As shown, the noise cancellation system <NUM> (not shown) may include at least a first microphone array <NUM> including at least two microphones - a first microphone 810a and a second microphone 810b - mounted to a bottom surface <NUM> of an external surface <NUM> of a first headrest <NUM>. Similar to <FIG>, the first and second microphones 810a,b may be spaced apart in a longitudinal direction with respect to the vehicle <NUM>. Thus, a distance separating the first and second microphones 810a,b may include at least a longitudinal distance X to create at least a first listening zone <NUM> and a second listening zone <NUM> oriented in the longitudinal direction. As described with respect to <FIG>, the digital signal processor <NUM> may be programmed to receive microphone signals indicative of sound from the microphone array <NUM>, as shown in <FIG>, and identify whether the sound is received from a direction of the first listening zone <NUM> or the second listening zone <NUM> based on the microphone signals. Moreover, the digital signal processor <NUM> may suppress or cancel the microphone signals indicative of sound from (the direction of) the second listening zone <NUM>, which may be equated with unwanted or disturbing background noise. On the other hand, the digital signal processor <NUM> may transmit microphone signals indicative of sound from (the direction of) the first listening zone <NUM>, which may be equated with wanted, near-end speech, to a far-end participant in a communications exchange.

As shown in <FIG>, the first and second microphones 810a,b may also be spaced apart in a lateral direction with respect to the vehicle <NUM>. Thus, the distance separating the first and second microphones 810a,b may further include a lateral distance Y such that the first listening zone <NUM> comprises two listening subzones oriented in a lateral direction with respect to the vehicle <NUM>. For instance, a first listening subzone 820a may encompass a region surrounding a driver's seat <NUM>, while a second listening subzone 820b may encompass a region surrounding a front passenger seat <NUM>. The lateral distance Y between the two microphones 810a,b in the first microphone array <NUM> may give an indication of the direction of incoming sound, generally left or right, such that the digital signal processor <NUM> may further identify whether the sound is received from a direction of the first listening subzone 820a or the second listening subzone 820b based on the microphone signals. Moreover, the digital signal processor <NUM> may be programmed to suppress or cancel microphone signals indicative of sound from (the direction of) the second listening subzone 820b, which may also be equated with unwanted or disturbing background noise. On the other hand, the digital signal processor <NUM> may transmit microphone signals indicative of sound from (the direction of) the first listening subzone 820a, which may be equated with wanted, near-end speech, to a far-end participant in a communications exchange.

As is further shown in <FIG>, the noise cancellation system may include a second microphone array <NUM> including at least two microphones - a first microphone 828a and a second microphone 828b - mounted to a bottom surface <NUM> of a second headrest <NUM>, which is laterally adjacent to the first headrest <NUM>. The second microphone array's configuration may mirror that of the first microphone array. Accordingly, the first and second microphones 828a,b in the second microphone array <NUM> may be also be spaced apart in both the longitudinal direction and the lateral direction to give further indication of the direction of incoming sound, generally left or right, such that the digital signal processor <NUM> may further identify whether the sound is received from a direction of the first listening subzone 820a or the second listening subzone 820b based on the microphone signals. The microphones in the first and/or second microphone arrays may be either omnidirectional or directional microphones.

<FIG> depicts yet another sample microphone configuration similar to the three-zone configuration shown in <FIG>. As shown, a first microphone array <NUM> may be mounted to an inboard side surface <NUM> of a headrest <NUM>, such as the microphone array shown in <FIG>. Similar to <FIG>, the first microphone array <NUM> may include a first microphone 910a and a second microphone 910b positioned on the inboard side surface <NUM> at spaced-apart locations, separated by a distance in the longitudinal direction to give an indication of the direction of incoming sound, forward or rearward. Thus, as previously described, the longitudinal separation of the first and second microphones 910a,b may create a first listening zone <NUM> and a second listening zone <NUM> oriented in the longitudinal direction. A second microphone array <NUM>, including first and second microphones 934a,b, may be disposed in a rearview mirror assembly <NUM> rather than in the second headrest (as in <FIG>) to give an indication of the direction of incoming sound, left or right, such that the digital signal processor <NUM> may further identify whether the sound is received from a direction of a first listening subzone 920a or a second listening subzone 920b based on the microphone signals. The first and second microphones 910a,b in the first microphone array <NUM> may be omnidirectional microphones. Moreover, the first and second microphones 934a,b in the second microphone array <NUM> may be directional microphones.

Claim 1:
A noise cancellation system (<NUM>) for a vehicle (<NUM>) comprising:
at least one first microphone array (<NUM>, <NUM>) having at least two microphones (710a, 710b) mounted to a first headrest (<NUM>, <NUM>) and spaced apart in a longitudinal direction, wherein a distance separating the two microphones (710a, 710b) is used to create at least a first listening zone (<NUM>) and a second listening zone (<NUM>), wherein the second listening zone (<NUM>) is oriented in the longitudinal direction relative to the first listening zone (<NUM>); and
a digital signal processor (<NUM>) programmed to:
receive microphone signals indicative of sound from the at least one first microphone array (<NUM>, <NUM>);
identify whether the sound is received from the first listening zone (<NUM>) or the second listening zone (<NUM>) based on the microphone signals by comparing the microphone signals from the two microphones (710a, 710b) and localizing a direction of the sound from either the first listening zone (<NUM>) or the second listening zone (<NUM>) based on a time difference of arrival of the microphone signals at each of the two microphones (710a, 710b);
transmit the microphone signals in case of the localizing the direction of the sound from the first listening zone (<NUM>); and
suppress or cancel the microphone signals in case of the localizing the direction of the sound from the second listening zone (<NUM>).