Occupancy-Based Active Noise Cancellation System

Abstract

The active noise cancellation (ANC) system is provided with at least one loudspeaker for projecting an anti-noise sound within a vehicle cabin in response to receiving an anti-noise signal. The at least one microphone provides an error signal indicative of noise within the cabin and the anti-noise sound. The occupancy controller is programmed to modify a transfer function between the at least one microphone and the at least one virtual microphone based on the occupancy signal indicative of a presence of an occupant within the cabin. The adaptive filter controller is programmed to filter the error signal using the transfer function to obtain an estimated virtual microphone error signal. The controllable filter generates the anti-noise signal based on the estimated virtual microphone error signal.

Description

[Technical field]

[0001] The present disclosure is directed to active noise cancellation systems, and more particularly, to controlling an active noise control framework including a virtual microphone based on vehicle occupancy. [Background technology]

[0002] Active noise cancellation (ANC) systems adaptively eliminate unwanted noise in a listening environment, such as a vehicle interior, by attenuating unwanted noise using feedforward and feedback structures. Typically, ANC systems cancel or reduce unwanted noise by generating cancellation sound waves that destructively interfere with the unwanted audible noise. Destructive interference occurs when a noise and an "anti-noise" (nearly identical in magnitude to the noise but in anti-phase) reduce the sound pressure level (SPL) at a location. In a vehicle interior listening environment, potential sources of unwanted noise are from sounds radiated by the engine, exhaust system, the interaction of the vehicle's tires with the road surface on which the vehicle travels, and / or vibrations of other parts of the vehicle. Thus, the unwanted noise varies with the vehicle's speed, road conditions, and operating conditions.

[0003] A road noise cancellation (RNC) system is a specific ANC system implemented in a vehicle to minimize unwanted road noise inside the vehicle cabin. An RNC system uses vibration sensors to sense road-induced vibrations occurring at the tire-road interface that result in unwanted audible road noise. This unwanted road noise inside the vehicle cabin is then canceled or reduced in level by using speakers to generate sound waves that are ideally in anti-phase and identical in magnitude to the noise to be reduced at one or more listeners' ears. Cancelling such road noise improves the ride comfort of vehicle passengers and allows automakers to use lighter materials, thereby reducing energy consumption and lowering emissions.

[0004] An Engine Order Cancellation (EOC) system is a specific ANC system implemented in vehicles to minimize undesirable engine noise inside the vehicle cabin. EOC systems use a non-acoustic signal, such as an engine speed sensor, to generate a signal representing the rotational speed of the engine crankshaft in revolutions per minute (RPM) as a reference. This reference signal is used to generate sound waves that are in anti-phase with the engine noise heard inside the vehicle. Because the EOC system uses a signal from the RPM sensor, the system does not require a vibration sensor.

[0005] RNC systems are typically designed to cancel wideband signals, while EOC systems are designed and optimized to cancel narrowband signals such as individual engine orders. An ANC system in a vehicle may provide both RNC and EOC technologies. Such vehicle-based ANC systems are typically least mean square (LMS) adaptive feedforward systems that continuously adapt the W-filter based on noise inputs (e.g., acceleration inputs from vibration sensors in the RNC system) and signals from physical microphones located at various locations in the vehicle's cabin. LMS-based feedforward ANC systems and corresponding algorithms are characterized by preserving the impulse response or secondary path between each physical microphone and each anti-noise speaker in the system. The secondary path is the transfer function between the anti-noise generating speaker and the physical microphone, and essentially characterizes how the electrical anti-noise signal becomes the sound radiated from the speaker, travels through the cabin to the physical microphone, and becomes the microphone output signal.

[0006] Virtual microphone is a technique in which an ANC system estimates an error signal generated by an imaginary or virtual microphone located where no real physical microphones are located, based on error signals received from one or more real physical microphones. This virtual microphone technique can improve noise cancellation at the listener's ears, even if the physical microphones are not actually located near the listener's ears. Summary of the Invention [Means for solving the problem]

[0007] In one embodiment, an active noise cancellation (ANC) system is provided with at least one loudspeaker for projecting an anti-noise sound within a vehicle cabin in response to receiving an anti-noise signal. The at least one microphone provides an error signal indicative of noise within the cabin and the anti-noise sound. The occupancy controller is programmed to modify a transfer function between the at least one microphone and the at least one virtual microphone based on the occupancy signal indicative of a presence of an occupant within the cabin. The adaptive filter controller is programmed to filter the error signal using the transfer function to obtain an estimated virtual microphone error signal. The controllable filter generates the anti-noise signal based on the estimated virtual microphone error signal.

[0008] In another embodiment, a method is provided for controlling a virtual microphone (VM) active noise cancellation (ANC) system. An error signal indicative of noise and anti-noise in a vehicle is received from a microphone. An occupancy signal indicative of the presence of an occupant in the vehicle is received from an occupancy detector. Based on the occupancy signal, a transfer function between the microphone and a virtual microphone is modified. The error signal is filtered using the transfer function to obtain an estimated virtual microphone error signal. An anti-noise signal radiated from a loudspeaker in the vehicle is generated based on the estimated virtual microphone error signal.

[0009] In yet another embodiment, an active noise cancellation (ANC) system is provided with an occupancy controller configured to modify a transfer function between at least one microphone and at least one virtual microphone based on the presence of an occupant in a passenger compartment of the vehicle. An adaptive filter controller is configured to filter an error signal indicative of noise and an anti-noise sound in the passenger compartment using the transfer function to obtain an estimated virtual microphone error signal. The ANC system is also provided with a controllable filter for generating an anti-noise signal based on the estimated virtual microphone error signal, providing the anti-noise signal to at least one loudspeaker, and projecting the anti-noise sound into the passenger compartment of the vehicle. The present specification also provides, for example, the following items: (Item 1) An active noise cancellation (ANC) system, at least one loudspeaker for projecting an anti-noise sound into a passenger compartment of the vehicle in response to receiving the anti-noise signal; at least one microphone for providing an error signal indicative of noise in the vehicle cabin and the anti-noise sound; an occupancy controller programmed to modify a transfer function between the at least one microphone and at least one virtual microphone based on an occupancy signal indicative of a presence of an occupant in the vehicle cabin; an adaptive filter controller programmed to filter the error signal using the transfer function to obtain an estimated virtual microphone error signal; a controllable filter for generating the anti-noise signal based on the estimated virtual microphone error signal; The active noise cancellation (ANC) system comprises: (Item 2) the at least one virtual microphone comprises a first virtual microphone and a second virtual microphone spaced apart from the first virtual microphone; 2. The ANC system of claim 1, wherein the occupancy controller is further programmed to modify the transfer function by increasing a gain associated with the first virtual microphone in response to an occupant being in proximity to the first virtual microphone. (Item 3) The at least one microphone comprises at least two microphones, and the adaptive filter controller further comprises: selecting one of the at least two microphones based on the occupancy signal; filtering the error signal from the selected microphone using the transfer function to obtain the estimated virtual microphone error signal; 2. The ANC system according to item 1, programmed to: (Item 4) The at least one loudspeaker comprises at least two loudspeakers, and the adaptive filter controller further comprises: selecting one of the at least two loudspeakers based on the occupancy signal; and generating the anti-noise signal to be radiated from the selected loudspeaker into the vehicle based on the estimated virtual microphone error signal; 2. The ANC system according to item 1, programmed to: (Item 5) 2. The ANC system of claim 1, wherein the adaptive filter controller is further programmed to determine a position of the at least one virtual microphone using head tracking technology. (Item 6) 2. The ANC system of claim 1, wherein the adaptive filter controller is further programmed to determine a position of the at least one virtual microphone based on a seat position. (Item 7) at least one sensor for providing a non-acoustic noise signal; a second secondary path filter configured to filter the non-acoustic noise signal to obtain a filtered noise signal, the second secondary path filter being defined by a stored transfer characteristic estimating a secondary path between the loudspeaker and the microphone; 2. The ANC system of claim 1, wherein the adaptive filter controller is further programmed to control the controllable filter based on the filtered noise signal and the estimated virtual microphone error signal. (Item 8) The at least one sensor comprises at least two sensors, and the adaptive filter controller further comprises: and programmed to select one of the at least two sensors based on a coherence of the sensor with at least one of the at least one microphone and the at least one virtual microphone; 8. The ANC system of claim 7, wherein the second secondary path filter is further configured to filter the non-acoustic noise signal from the selected sensor to obtain a filtered noise signal. (Item 9) 1. A method for controlling a virtual microphone (VM) active noise cancellation (ANC) system, comprising: receiving an error signal from a microphone indicative of noise and anti-noise within the vehicle; receiving an occupancy signal from an occupancy detector indicative of a presence of an occupant within the vehicle; modifying a transfer function between the microphone and a virtual microphone based on the occupancy signal; filtering the error signal using the transfer function to obtain an estimated virtual microphone error signal; generating an anti-noise signal based on the estimated virtual microphone error signal, the anti-noise signal being radiated from a loudspeaker into the vehicle; The method comprising: (Item 10) The virtual microphones include a first virtual microphone and a second virtual microphone spaced apart from the first virtual microphone, and modifying the transfer function further includes: 10. The method of claim 9, comprising increasing a gain associated with the first virtual microphone in response to a presence of an occupant proximate to the first virtual microphone. (Item 11) The microphone further includes at least two microphones, and the method further comprises: selecting one of the at least two microphones based on the occupancy signal; filtering the error signal from the selected microphone using a secondary path filter to obtain the estimated virtual microphone error signal; 10. The method according to item 9, comprising: (Item 12) The loudspeaker further comprises at least two loudspeakers, the method further comprising: selecting one of the at least two loudspeakers based on the occupancy signal; and generating the anti-noise signal to be radiated from the selected loudspeaker into the vehicle based on the estimated virtual microphone error signal; 10. The method according to item 9, comprising: (Item 13) 10. The method of claim 9, further comprising determining the position of the virtual microphone using head tracking technology. (Item 14) 10. The method of claim 9, further comprising determining a position of the virtual microphone based on a seat position. (Item 15) An active noise cancellation (ANC) system, an occupancy controller configured to modify a transfer function between the at least one microphone and the at least one virtual microphone based on a presence of an occupant within a cabin of the vehicle; an adaptive filter controller configured to filter an error signal indicative of noise and anti-noise sounds in the vehicle cabin using the transfer function to obtain an estimated virtual microphone error signal; generating an anti-noise signal based on the estimated virtual microphone error signal, providing the anti-noise signal to at least one loudspeaker, and a controllable filter for projecting an anti-noise sound into a vehicle cabin. (Item 16) Item 16. The ANC system of item 15, wherein the adaptive filter controller is further configured to modify the transfer function by increasing a gain associated with a first virtual microphone in response to an occupant being in proximity to the first virtual microphone. (Item 17) further comprising at least two microphones; The adaptive filter controller further comprises: selecting one of the at least two microphones based on a presence of the occupant; filtering the error signal from the selected microphone using the secondary path filter to obtain the estimated virtual microphone error signal; Item 16. The ANC system of item 15, configured to: (Item 18) further comprising at least two loudspeakers; The adaptive filter controller further comprises: selecting one of the at least two loudspeakers based on the presence of the occupant; and generating the anti-noise signal to be radiated from the selected loudspeaker into the vehicle based on the estimated virtual microphone error signal; Item 16. The ANC system according to item 15, configured to: (Item 19) Item 16. The ANC system of item 15, wherein the adaptive filter controller is further configured to determine the position of the at least one virtual microphone using head tracking technology. (Item 20) Item 16. The ANC system of item 15, wherein the adaptive filter controller is further configured to determine a position of the at least one virtual microphone based on a seat position. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is an environmental block diagram of a vehicle having an active noise cancellation (ANC) system including road noise cancellation (RNC), a virtual microphone, and an occupancy detector, in accordance with one or more embodiments.

[0011] [Diagram 2] FIG. 2 is a sample schematic diagram showing relevant portions of an RNC system scaled to include R accelerometer signals and L speaker signals.

[0012] [Diagram 3] FIG. 1 is a schematic block diagram of a sample ANC system including an engine order cancellation (EOC) system and an RNC system.

[0013] [Figure 4] 1 is a table of different vehicle occupancy configurations.

[0014] [Diagram 5] FIG. 1 is a schematic block diagram illustrating a virtual microphone ANC system including an occupancy controller in accordance with one or more embodiments.

[0015] [Figure 6] 1 is a flowchart illustrating a method for adjusting virtual microphone parameters based on vehicle occupancy in a virtual microphone ANC system in accordance with one or more embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Where necessary, detailed embodiments of the present disclosure are disclosed herein, but it should be understood that the disclosed embodiments are merely examples of the present disclosure, which may be embodied in various and alternative forms. The figures are not necessarily to scale, and some features may be exaggerated or minimized to show details of particular components. Thus, specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as representative underlying principles.

[0017] Referring to FIG. 1, a road noise cancellation (RNC) system is shown, generally designated 100, in accordance with one or more embodiments. The RNC system 100 is shown within a vehicle 102 having one or more vibration sensors 104. The vibration sensors 104 are positioned throughout the vehicle 102 to monitor the vibration behavior of the vehicle's suspension, subframe, and other axle and chassis components. The RNC system 100 may be integrated with a wideband adaptive feedforward and feedback active noise cancellation (ANC) system 106 that uses one or more physical microphones 108 to generate anti-noise by adaptively filtering signals from the vibration sensors 104. The anti-noise signal may then be reproduced by one or more loudspeakers or speakers 110 into a sound. S(z) represents the transfer function between a single speaker 110 and a single microphone 108. It should be noted that while only one each of vibration sensor 104, microphone 108, and speaker 110 are shown in Figure 1 for simplicity purposes only, multiple vibration sensors 104 (e.g., 10 or more), microphones 108 (e.g., 4-6), and speakers 110 (e.g., 4-8) are typically used in an RNC system. As will be described in more detail with reference to Figure 5, according to one or more embodiments, the ANC system 106 may also include one or more virtual microphones 112, 113, and one or more occupancy detectors 114, which adapt the anti-noise signal(s) to be optimized for the occupants of the vehicle 102 at a given time.

[0018] The vibration sensors 104 include, but are not limited to, accelerometers, force gauges, geophones, linear variable differential transformers, strain gauges, and load cells. An accelerometer, for example, is a device whose output signal amplitude is proportional to acceleration. A variety of accelerometers can be used in an RNC system. These include accelerometers that are typically sensitive to vibrations in one, two, or three orthogonal directions. These multi-axis accelerometers typically provide separate electrical outputs (or channels) for vibrations sensed in their X, Y, and Z directions. Thus, single-axis and multi-axis accelerometers may be used as vibration sensors 104 to detect the magnitude and phase of acceleration and to sense orientation, motion, and vibration.

[0019] Noise and vibration resulting from the wheels 116 moving on the road surface 118 may be sensed by one or more vibration sensors 104 mechanically coupled to a suspension device 119 or chassis components of the vehicle 102. The vibration sensor 104 may output a noise signal X(n), which is a vibration signal representative of the detected road-induced vibration. It should be noted that there may be multiple vibration sensors, and their signals may be used separately or in combination. In certain embodiments, a microphone may be used instead of a vibration sensor to output a noise signal X(n) indicative of the noise generated from the interaction of the wheels 116 with the road surface 118. The noise signal X(n) may be filtered with a modeled transfer characteristic S'(z), which estimates the secondary path (i.e., the transfer function between the anti-noise speaker 110 and the physical microphone 108) by a secondary path filter 120.

[0020] Road noise resulting from the interaction of the wheels 116 with the road surface 118 is also transmitted, mechanically and / or acoustically, into the passenger compartment and received by one or more microphones 108 inside the vehicle 102. The one or more microphones 108 may be located, for example, in the headliner of the vehicle 102, or in some other suitable location that senses the acoustic noise field heard by occupants within the vehicle 102, such as occupants sitting in the rear seats 125. The road noise resulting from the interaction of the road surface 118 with the wheels 116 is transmitted to the microphones 108 according to a transfer characteristic P(z), which represents the primary path (i.e., the transfer function between the actual noise source and the physical microphone).

[0021] The microphone 108 may output an error signal e(n) representative of the sound present in the cabin of the vehicle 102 detected by the microphone 108, including noise and anti-noise. In the RNC system 100, the adaptive transfer characteristic W(z) of the controllable filter 126 may be controlled by an adaptive filter controller 128, which may operate according to a known least mean square (LMS) algorithm based on the error signal e(n) and the noise signal X(n) filtered with the transfer characteristic S'(z) modeled by the filter 120. The controllable filter 126 is often referred to as a W-filter. The anti-noise signal Y(n) may be generated by an adaptive filter formed by the controllable filter 126 and the adaptive filter controller 128 based on the identified transfer characteristic W(z) and the vibration signal, or a combination of the vibration signal X(n). The waveform of the anti-noise signal Y(n) is ideally such that when the anti-noise signal Y(n) is played through the speaker 110, the anti-noise generated near the ears of the vehicle cabin occupants and the microphone 108 is substantially anti-phase and identical in magnitude to the road noise heard by the vehicle cabin occupants. The anti-noise from the speaker 110 may be combined with the road noise in the vehicle cabin near the microphone 108 to reduce the road noise induced sound pressure level (SPL) at this location. In certain embodiments, the RNC system 100 may receive sensor signals from other acoustic sensors in the vehicle cabin, such as acoustic energy sensors, acoustic intensity sensors, or acoustic particle velocity or acceleration sensors, and generate the error signal e(n).

[0022] During operation of the vehicle 102, the processor 130 may collect and process data from the vibration sensor(s) 104 and microphone(s) 108 as necessary to build and / or modify a database or map containing the data and / or parameters used by the vehicle 102. The collected data may be stored locally in the storage 132 or in the cloud for later use by the vehicle 102. For example, types of RNC system 100 related data that may be useful to store locally in the storage 132 may include, but are not limited to, occupancy configuration data related to the secondary path, i.e., the transfer function H(z) between the physical microphone positions and the virtual microphone positions, the preferred physical microphone set, and the preferred speaker set. In one or more embodiments, the processor 130 and storage 132 may be integrated with one or more RNC system controllers, such as the adaptive filter controller 128.

[0023] As mentioned above, the RNC system may typically use several vibration sensors, microphones, and speakers to sense vibration behavior caused by the vehicle's structure and generate anti-noise. The vibration sensor may be a multi-axis accelerometer with multiple output channels. For example, a three-axis accelerometer typically has separate electrical outputs for vibrations sensed in the X, Y, and Z directions. A typical configuration of the RNC system may have, for example, six physical microphones, six speakers, and twelve channels for acceleration signals from four three-axis accelerometers or six two-axis accelerometers. Thus, the RNC system also includes multiple S'(z) filters (i.e., secondary path filters 120) and multiple W(z) filters (i.e., controllable filters 126).

[0024] The simplified RNC system schematic shown in FIG. 1 shows one secondary path between the speaker 110 and the microphone 108, represented by S(z). As previously mentioned, an RNC system typically has multiple speakers, microphones, and vibration sensors. Thus, an RNC system with six speakers and six microphones would have a total of 36 (i.e., 6×6) secondary paths. Correspondingly, an RNC system with six speakers and six microphones would similarly have 36 S′(z) filters (i.e., secondary path filters 120) that estimate transfer functions for each of the secondary paths. As shown in FIG. 1, the RNC system would also have one W(z) filter (i.e., controllable filter 126) between each of the noise signals X(n) from the vibration sensors (i.e., accelerometers) 104 and each of the speakers 110. Thus, an RNC system with 12 accelerometer signals and six speakers would have 72 W(z) filters. The relationship between the number of accelerometer signals, the number of speakers, and the number of W(z) filters is shown in FIG.

[0025] FIG. 2 shows R accelerometer signals [X 1 (n), X 2 (n), …X R (n)] and L speaker signals [Y 1 (n), Y 2 (n), …Y LFIG. 1 is a sample schematic diagram showing relevant portions of an RNC system 200 scaled to include R*L controllable filters (or W filters) 226 between each of the accelerometer signals and each of the speakers. As an example, an RNC system with 12 accelerometer outputs (i.e., R=12) may use six two-axis accelerometers or four three-axis accelerometers. In the same example, six speakers (i.e., L=6) for playing anti-noise may therefore use a total of 72 W filters. At each of the L speakers, the outputs of the R W filters are summed to generate the anti-noise signal Y(n) for the speaker. Each of the L speakers may include an amplifier (not shown). In one or more embodiments, the R accelerometer signals filtered by the R W filters are summed to generate an electrical anti-noise signal y(n), which is sent to an amplifier to generate an amplified anti-noise signal Y(n) to be sent to the speaker.

[0026] The ANC system 106 shown in FIG. 1 may also include an engine order cancellation (EOC) system. As mentioned above, EOC technology uses a non-acoustic signal, such as an engine speed signal representing the rotational speed of the engine crankshaft, as a reference to generate a sound that is in phase with the engine noise heard inside the vehicle. The EOC system may utilize a narrowband feed-forward ANC framework to generate the anti-noise, using the engine speed signal to guide the generation of an engine order signal at the same frequency as the engine order to be canceled, and adaptively filtering it to create the anti-noise signal. The anti-noise, after being transmitted from the anti-noise source to the listening position or physical microphone via a secondary path, is ideally of the same amplitude and in phase with the combined engine and exhaust sound generated after being filtered by the primary path extending from the engine to the listening position and from the exhaust outlet to the listening position or physical or virtual microphone position. Therefore, at the location of the physical microphone in the vehicle cabin (i.e., most likely at or near the listening position), the engine order noise and anti-noise are superimposed and ideally zero, so that the acoustic error signal received by the physical microphone records only sounds excluding the engine order or multiple engine orders generated by the engine and exhaust (ideally canceled).

[0027] Typically, a non-acoustic sensor such as an engine speed sensor is used as the reference. For example, the engine speed sensor can be a Hall effect sensor mounted adjacent to a rotating steel disk. Other detection principles such as optical or inductive sensors can also be used. The signal from the engine speed sensor can be used as a guide signal to generate any number of reference engine order signals corresponding to each of the engine orders. The reference engine orders form the basis of the noise cancelling signals generated by one or more narrowband adaptive feedforward LMS blocks that form the EOC system.

[0028] 3 is a schematic block diagram illustrating an example of an ANC system 306 that includes both an RNC system 300 and an EOC system 340. Similar to the RNC system 100, the RNC system 300 may include a vibration sensor 304, a physical microphone 308, a w-filter 326, an adaptive filter controller 328, a secondary path filter 320, and a speaker 310, each consistent with the operation of the vibration sensor 104, physical microphone 108, w-filter 126, adaptive filter controller 128, secondary path filter 120, and speaker 110 described above.

[0029] The EOC system 340 may include an engine speed sensor 342 to provide an engine speed signal 344 (e.g., a square wave signal) indicative of the rotation of the engine crankshaft or the rotation of a drive shaft, half shaft, or other shaft whose rotational speed coincides with the vibration of the vehicle components that cause interior noise. In some embodiments, the engine speed signal 344 may be obtained from a vehicle network bus (not shown). Since the emitted engine orders are directly proportional to the RPM of the crankshaft, the engine speed signal 344 represents the frequencies generated by the engine and exhaust system. Thus, the signal from the engine speed sensor 342 may be used to generate a reference engine order signal corresponding to each of the engine orders of the vehicle. Thus, the engine speed signal 344 may be used in conjunction with a lookup table 346 of engine speed (RPM) versus engine order frequency that provides a list of engine orders emitted at each engine speed. The adaptive filter controller 328 may take the engine speed (RPM) as an input and generate a sine wave for each order based on the lookup table 346.

[0030] The frequency of a given engine order at a sensed engine speed (RPM) obtained from the lookup table 346 may be provided to a frequency generator 348 to generate a sine wave at the given frequency. This sine wave represents a noise signal X(n) indicative of engine order noise for the given engine order. Similar to the RNC system 300, this noise signal X(n) from the frequency generator 348 may be sent to an adaptive controllable filter 326 or W filter that provides a corresponding anti-noise signal Y(n) to the speaker 310. As shown, various components of this narrowband EOC system 340 may be identical to the wideband RNC system 300, including the physical microphone 308, adaptive filter controller 328, and secondary path filter 320. The anti-noise signal Y(n) spread by the speaker 310 generates an anti-noise that is substantially out of phase with, but identical in magnitude to, the actual engine order noise at the listener's ear location, which may be proximate to the physical microphone 308, thereby reducing the engine order sound amplitude. Because engine order noise is narrowband, the error signal e(n) may be filtered by a bandpass filter 350 before being passed to the LMS-based adaptive filter controller 328. In one embodiment, the LMS adaptive filter controller 328 works well if the noise signal X(n) output by the frequency generator 348 is bandpass filtered using the same bandpass filter parameters.

[0031] To simultaneously reduce the amplitude of multiple engine orders, the EOC system 340 may include a multiple frequency generator 348 for generating a unique noise signal X(n) for each engine order based on the engine speed (RPM) signal 344. By way of example, FIG. 3 illustrates a multiple frequency generator 348 for generating a unique noise signal (e.g., X(n) for each engine order based on the engine speed (RPM) signal 344. 1 (n), X 23 shows a second-order EOC system having two frequency generators that generate two engine orders (e.g., 1(n)). Since the frequencies of the two engine orders are different, the bandpass filters 350 (labeled BPF and BPF2) have different high-pass and low-pass filter corner frequencies. The number of frequency generators and corresponding noise cancellation components varies depending on the number of engine orders to be canceled for a particular engine of the vehicle. As the EOC system for two orders 340 is combined with the RNC system 300 to form the ANC system 306, the anti-noise signals Y(n) output from the three controllable filters 326 are summed and sent to the speaker 310 as the speaker signal S(n). Similarly, the error signal e(n) from the physical microphone 308 can be sent to three LMS adaptive filter controllers 328.

[0032] If the modeled transfer characteristic S'(z) representing the estimated secondary path stored in the ANC system does not match the actual secondary path of the system, it may result in poor noise cancellation performance, noise gain, or actual instability. As mentioned above, the secondary path is the transfer function between the anti-noise generating speaker and the physical microphone. It therefore essentially characterizes the behavior of the electrical anti-noise signal Y(n) as it becomes the sound radiated from the speaker, which then travels through the vehicle cabin to the physical microphone and becomes part of the microphone output or error signal e(n). If the vehicle differs significantly from the reference vehicle or system in terms of geometry, number of passengers, luggage load, etc., the actual secondary path S(z) may deviate from the stored secondary path model S'(z), which is usually measured on a "golden system" by trained engineers. In an embodiment, a vehicle with occupancy detection can select an appropriate set of secondary paths from a predefined stored database to improve the performance of the noise cancellation system.

[0033] ANC systems generate anti-noise that is ideally anti-phase and identical in magnitude to the noise being reduced at one or more listeners' ears. Existing ANC systems often generate a zone of reduced noise ("quiet zone") around the location(s) of the physical microphone. The quiet zone is a small quiet zone that is approximately one-tenth of an acoustic wavelength in size and decreases in size as frequency increases. When using only one physical microphone in a vehicle application, moving the ear away from the microphone produces an abrupt change in performance, especially when the ear is more than one-tenth of a wavelength away. Furthermore, a system with one physical microphone is likely to increase sound pressure levels everywhere else in the vehicle. To avoid this "noise boosting" at the location of the first or second vehicle occupant, active systems use four or six physical microphones to reduce the noise field more uniformly throughout the vehicle cabin. To maximize the perceived possible noise cancellation, the physical microphones are ideally mounted at the occupant's ear locations. However, in practice, it is often not possible to place physical microphones near the ears of all vehicle occupants due to vehicle spatial design limitations such as convertible tops, sunroofs, and lack of microphones mounted on the seats, all of which can make it difficult to achieve maximum noise field reduction at the most important location, the vehicle occupants' ears.

[0034] 1 , the vehicle 102 includes a physical microphone 108 located in the headliner. The physical microphone 108 is not located at the ears of the passengers sitting in the rear seats 125. However, the ANC system 106 includes a virtual microphone 112 located at the ears of the passengers sitting in the rear seats 125.

[0035] Virtual microphone is a technique in which an ANC system estimates a generated error signal at a location where no real physical microphone is located by an imaginary or virtual microphone based on the error signal received from one or more real physical microphones. This virtual microphone technique can improve noise cancellation at the passenger's ears even if the physical microphone is not actually located at the ear. Another advantage of the virtual microphone technique is that it provides a flexible solution for the mounting location of the physical microphone. Compared with traditional non-virtual noise cancellation algorithms, the virtual microphone algorithm can estimate the estimated virtual signal as an error signal e. v (n). Based on the virtual error signal estimation, the virtual microphone algorithm adapts the W filter based on the estimated virtual error signal instead of the physical error signal. Thus, the performance of the noise cancellation system is maximized with these virtual microphones ideally located near the actual ears of the listener, e.g., near the headliner of the vehicle, instead of the physical microphone locations, which may be far away from the listener's ears. Vehicles with headrest-mounted microphones can benefit from the virtual microphone technology, since the virtual microphones can be located closer to the occupant's ears than the headrest-mounted microphones.

[0036] Referring to FIG. 4, a vehicle may allow for multiple different vehicle occupancy configurations, which may make it difficult for an ANC system to determine the ear positions of vehicle passengers. FIG. 4 is a table 400 illustrating different occupancy configurations for a vehicle having five seats: a driver's seat (D), a front passenger seat (FP), a first rear seat (RP1), a second rear seat (RP2), and a third rear seat (RP3). Such a vehicle may include a single first configuration (1A) with one occupant, multiple second configurations (2A-2D) with two occupants, multiple third configurations (3A-3X) with three occupants, multiple fourth configurations (4A-4X) with four occupants, and a single fifth configuration (5A) with five occupants. In the first configuration (1A), the driver's seat (D) is occupied (O), but all passenger seats are unoccupied (X). In a first second configuration 2A (shown in FIG. 4), the driver's seat (D) and the front passenger seat (FP) are occupied. In a third second configuration 2C (not shown), the driver's seat (D) and the second rear seat (RP2) are occupied. A virtual microphone located at the ear of a passenger sitting in the front passenger seat (FP) is not optimal for a passenger sitting in the second rear seat (RP2) and vice versa.

[0037] Although an ANC system may include many speakers capable of radiating anti-noise to passengers, there is a limit to the anti-noise signal that can be generated at one time due to system hardware or software limitations, such as the million instructions per second (MIPS) limit of a digital signal processor (DSP) chip and the limited number of output channels of an algorithm. Speakers closer to the front passenger seat can radiate anti-noise to the front passenger seat more effectively and provide better noise cancellation than speakers further away radiating anti-noise to the front passenger seat. In such an occupied case, more speakers can be provided to radiate anti-noise than the front passenger seats, and the number of speakers radiating anti-noise can be reduced for speakers located near the vacant rear seats.

[0038] Furthermore, in an ANC system, many physical microphones may be installed in a vehicle, but there may be limitations on the number of physical microphone channels that the system can use simultaneously due to limitations in ADC, amplifier / algorithm / DSP chip MIPS, or other design constraints. In an effort to provide optimal noise cancellation for an occupied seat when only the front seats are occupied, an extra microphone near the front seat passenger may be selected to output the noise signal e(n) to the noise cancellation algorithm, instead of one or more microphones near the vacant (rear) seat.

[0039] Similarly, an accelerometer (noise) reference channel may be provided, but due to hardware input or MIPS limitations, fewer channels may be simultaneously usable by the noise cancellation system. If only the front seats are occupied, an extra reference signal from the front of the vehicle may be used in place of one or more reference signals originating from the rear of the vehicle. In one or more embodiments, the reference signal is selected from the sensor that has the highest coherence with the physical or virtual microphone closest to the occupied seat, regardless of how close it is to the occupied seat.

[0040] Referring again to FIG. 1, the vehicle 102 includes an occupancy detector 114 that provides an occupancy signal (Occ) indicating whether the front seat 124 is occupied. Although only one occupancy detector 114 is shown in FIG. 1, the ANC system 106 may include one or other number of occupancy detectors 114 for each seat. The occupancy detector 114 may include a number of sensors and / or technologies, such as seat belt sensors, seat sensors, proximity sensors, load cells, motion sensors, cameras with machine vision systems, cameras with facial recognition or infrared (IR) imaging capabilities, passive infrared (PIR) sensors, or infrared or near infrared sensors for detecting heat responses. In one embodiment, the occupancy detector 114 may include a microphone or microphone array adapted to function as an occupancy sensor and optionally coupled with an adaptive beamformer. The ANC system 106 may allow a user to manually input occupancy information via a user interface, such as buttons or a touch screen option.

[0041] The ANC system 106 may detect which vehicle seats are occupied using a variety of methods, including sensors, sensor arrays, sensor fusion, and voice recognition. The ANC system 106 then selects the optimal noise cancellation tuning for a given occupancy configuration using a combination of physical microphones, virtual microphones, accelerometer sensors, physical and virtual secondary paths, transfer functions, tuning parameters, and speakers. In one embodiment, the ANC system 106 includes a camera (not shown) or other equipment to determine the virtual microphone position using head tracking techniques to determine the location of the occupant's ear canal opening.

[0042] The ANC system may achieve optimal performance when the location of each occupant's ear in three-dimensional space coincides with a virtual microphone. The ANC system may achieve improved performance over conventional non-virtual microphone techniques when the location of the virtual microphone is closer to the ear location than the physical microphone. Other techniques for selecting the virtual microphone location include the use of a seat position encoder. The ANC system may use current seat position data to estimate the location of the seat occupant's ear in three dimensions and select the virtual microphone location closest to the occupant's ear, for example by selecting a low virtual microphone location for a forward seat location and a high virtual microphone location for a rear seat location. The virtual microphone location may be pre-determined by the ANC system tuning engineer when tuning the ANC system, and the selection of the virtual microphone location includes determining which virtual microphone is closest to the ear location in three-dimensional space.

[0043] FIG. 5 is a schematic block diagram of a vehicle-based virtual microphone (VM) ANC system 506 illustrating many of the important ANC system parameters that may be used to estimate a virtual microphone error signal based on vehicle occupancy to optimize ANC system performance. For ease of explanation, the VM-ANC system 506 illustrated in FIG. 5 is illustrated with the components and functionality of an RNC system 500 and an EOC system 540. Thus, the VM-ANC system 506 is a schematic diagram of an RNC system and / or an EOC system such as those described with respect to FIGS. 1-3, with the additional system components of the VM-ANC system 506 including a virtual microphone 512 and an occupancy detector 514. Similar components may be numbered using similar conventions. For example, similar to ANC system 106, ANC system 506 may include a vibration sensor 504, a physical microphone 508, a w-filter 526, an adaptive filter controller 528, a virtual secondary path filter 520, and a speaker 510, each consistent with the operation of vibration sensor 104, physical microphone 108, w-filter 126, adaptive filter controller 128, secondary path filter 120, and speaker 110 described above. Also shown in Figure 5 for illustrative purposes in block form are the primary path P(z) and secondary path S(z), as described with respect to Figure 1.

[0044] The physical microphone 508 receives disturbance signals that are intended to be cancelled, including road noise, engine and exhaust noise. p (n), and anti-noise from speaker 510 p (n) and any external sounds at the microphone position, p (n) to provide.

[0045] The virtual microphone 512 receives the disturbance signal d to be cancelled, which includes road noise, engine and exhaust noise. v (n), and anti-noise from speaker 510 vrepresents a microphone at a virtual microphone position that senses all sounds at that position in the same way, including sounds from the physical microphones (n) and external sounds. Typically, there will be multiple physical microphone positions and multiple virtual microphone positions. Note that when the noise cancellation system operates, no actual microphones are attached to the virtual microphone positions. Thus, using the virtual microphone technique, the pressure at the virtual microphone position is estimated from the pressure at the physical microphone position, and an estimated error signal e' v (n) is formed.

[0046] The physical microphone 508 detects the noise d(z) that propagates from the noise source 542 to its position along the primary path P(z) 544. p (n) and the anti-noise y transmitted from the speaker 510 to the location along the secondary path Se(z) 546. p The physical microphone 508 senses both the physical error signal e(n) as shown by Equation 1. p (n) to provide. e p (n)=d p (n)+y p (n)(1)

[0047] In block 548, the VM-ANC system 506 calculates the disturbance noise d' to be cancelled at the physical microphone position. p The VM-ANC system 506 estimates the physical error signal e(n) as shown by Equation 2. p From (n), the anti-noise y' at the physical microphone position p By subtracting the estimated value of (n), the disturbance noise d' at the physical microphone position is obtained. p Estimate (n). d' p (n)=e p (n)-y' p (n)(2)

[0048] Next, in block 550, the VM-ANC system 506 calculates the estimated disturbance noise d′ p The disturbance noise d'(n) is cancelled at the virtual microphone position by convolving the transfer function H(z) 550 between the physical microphone position and the virtual microphone position. v (n). The VM-ANC system 506 includes an occupancy controller 552 that receives an occupancy signal (Occ) from the occupancy detector 514 and adjusts tuning parameters such as the H-filter, secondary path, primary error signal, virtual error signal, speaker noise signal, and reference noise signal based on the current occupancy configuration of the vehicle. For example, gain may be applied to physical or virtual error signals located near occupied seats relative to physical or virtual error signals from near unoccupied seats. Similarly, the VM-ANC system 506 may apply attenuation to physical or virtual error signals near one or more unoccupied seats. This causes the LMS system 528 to adapt the W-filter 526 to increase noise cancellation in areas of the vehicle that are close to the occupied seats.

[0049] In block 554, the VM-ANC system 506 calculates the estimated disturbance noise d′ to be cancelled at the virtual microphone position, as shown by Equation 3. v (n) is the anti-noise estimate y' at this position v (n), the virtual microphone error signal e' that would be present at the virtual microphone v Estimate (n). e' v (n)=d' v (n)+y' v (n)(3)

[0050] By combining Equation 1, Equation 2, and Equation 3, an estimate of the virtual error microphone signal is created from the physical error signal, the secondary paths of the physical and virtual microphones, and the transfer function between the physical and virtual positions.

[0051] Similar to FIG. 1, a noise signal X(n) from a noise input such as a vibration sensor 504 is filtered by a virtual secondary path filter 520 to generate a modeled transfer characteristic S' using the stored virtual secondary path estimates described above. v (z) to obtain a filtered noise signal X'(n). Further, the transfer characteristic W(z) of a controllable filter 526 (e.g., a W filter) may be controlled by an LMS adaptive filter controller (or simply, an LMS controller) 528 to provide an adaptive filter. The LMS adaptive filter controller 528 filters the filtered noise signal X'(n) and the estimated virtual error signal e' v (n) and adapts the W filter for optimized noise cancellation at the location of the virtual microphone. The controllable filter 526 generates an anti-noise signal Y(n) based on the output of the LMS controller 528 and the noise signal X(n).

[0052] 2, the VM-ANC system 506 is scaled to include R accelerometer signals, L loudspeaker or speaker signals, and M microphone error signals. Thus, the VM-ANC system 506 may include R×L controllable filters (or W filters) 526 and L×M anti-noise signals.

[0053] 6 is a flow chart illustrating a method 600 for adjusting virtual microphone system parameters based on vehicle occupancy in a virtual microphone ANC system in accordance with one or more embodiments of the present disclosure. Various steps of the disclosed method may be performed by the adaptive filter controller 528 alone or in combination with other components of the VM-ANC system 506.

[0054] In step 602, the VM-ANC system 506 receives input from the occupancy detector 514 indicating which seats in the vehicle are occupied. Then, in step 604, the occupancy controller 552 determines an occupancy configuration based on the input, for example, one of the configurations shown in FIG. 4. In step 606, the VM-ANC system 506 compares the occupancy configuration to a last saved occupancy configuration to determine whether the occupancy configuration has changed. If the configuration has not changed, the VM-ANC system 506 returns to step 602. If the configuration has changed, the VM-ANC system 506 proceeds to step 608 and adjusts one or more VM-ANC system parameters.

[0055] In step 608, the VM-ANC system 506 adjusts the anti-noise signal Y(n) provided to the one or more speakers 510 based on the current occupancy configuration. The occupancy controller 552 may include predefined stored data indicating optimal transfer function parameters, such as an H-filter, for each occupancy configuration based on the hardware and software limitations of the system 506. The transfer function may include one or more virtual microphone transfer functions H(z) 550, one or more physical microphone transfer functions, or a combination of both virtual and physical microphone transfer functions. In one embodiment, a set of virtual microphones, physical microphones, speakers, noise signals, virtual secondary paths, physical secondary paths, physical or virtual microphone gains, accelerometer gains, other LMS system tuning parameters, and H(z) transfer functions are stored in a database for each occupancy configuration, and in step 608, the VM-ANC system 506 selects the complete set of parameters from the database. In another embodiment, the database stores only a subset of the aforementioned VM-ANC system parameters.

[0056] Many of the parameters in the VM-ANC system 506 are linked together, and thus the VM-ANC system 506 may vary multiple parameters in tandem in step 608. In one embodiment, when the VM-ANC system 506 modifies the configuration of the virtual microphone 512, the virtual secondary path S' v In another embodiment, when the VM-ANC system 506 modifies the configuration of the virtual microphone 508, the virtual secondary path S′ is also modified based on the modified configuration. p In another embodiment, the VM-ANC system 506 also modifies the microphone transfer function H(z) 549 and the microphone transfer function H(z) 550. In another embodiment, instead of a specific “inactive” error signal, the VM-ANC system 506 modifies the same physical error signal e p In another embodiment, when the VM-ANC system 506 modifies the configuration of the speakers 510, the VM-ANC system 506 uses multiple copies of the physical secondary path S'(n) based on the modified configuration. p (z)549 and virtual secondary route S' v (z) 520. In one embodiment, in the VM-ANC system 506, the configuration of the noise signal X(n) is modified and the W filter 526 is reset or modified based on the modified configuration.

[0057] In one or more embodiments, when the vehicle is in a fully unoccupied configuration, the VM-ANC system 506 selects a number of virtual microphones near the occupied seats to improve noise cancellation at the occupied seats, in part by ensuring that the system is not overly constrained by noise cancellation in unoccupied areas of the vehicle. In one embodiment, one or more virtual microphone locations are chosen around the headrest of each seat, and an associated transfer function S' is calculated for each of the system's speakers and physical microphones. v In an embodiment with only one occupant, the eight virtual microphones e' v (n) All signals are located close to the driver and in a position that surrounds the occupant's head.

[0058] Although the VM-ANC system 506 has been described with reference to a virtual microphone, in other embodiments of the ANC system, a remote microphone (RM) provides the RM-ANC system. A remote microphone has a transfer function H(z) whose value is different from the virtual microphone. The VM-ANC system 506 includes an H(z) whose value is unity or 1. This means that any difference in disturbance signals that are cancelled between the physical and virtual positions is simply ignored. The RM-ANC system includes a transfer function H(z) that is not equal to unity. This means that any difference in disturbance signals that are cancelled between the physical and virtual positions is taken into account. The various embodiments described herein using the term virtual microphone system or technology are all applicable to remote microphone technology, with one modification being the value of H(z).

[0059] Although the ANC system is described with reference to a vehicle application, the techniques described herein are applicable to non-vehicle applications. For example, a room may have fixed seats with defined listening positions where disturbing sounds should be quieted using a reference sensor, an error sensor, a speaker, and an LMS adaptation system. Note that the disturbance noise to be cancelled is likely to be of a different type, such as HVAC noise or noise from an adjacent room or space. Furthermore, the room may have occupants whose positions change over time, and selecting the three-dimensional position of the virtual microphone requires the position of the listener or listeners to be determined by the seat sensor or head tracking techniques described herein.

[0060] 1, 3, and 5 show LMS-based adaptive filter controllers 128, 328, and 528, respectively, other methods and apparatus for creating and adapting the optimal controllable W filters 126, 326, and 526 are possible. For example, in one or more embodiments, a neural network may be used to create and optimize the W filters instead of an LMS adaptive filter controller. In other embodiments, machine learning or artificial intelligence may be used to create the optimal W filters instead of an LMS adaptive filter controller.

[0061] Any one or more of the controllers or devices described herein include computer programs compiled or translated with computer-executable instructions created using various programming languages ​​and / or technologies. Generally, a processor (such as a microprocessor) receives instructions from, for example, a memory, a computer-readable medium, etc., and executes the instructions. The processing unit includes a non-transitory computer-readable storage medium capable of executing the instructions of a software program. Computer-readable storage media include, but are not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination thereof.

[0062] For example, the steps recited in any method or process claim may be performed in any order and are not limited to the particular order presented in the claims. Averaging may be performed using a filter to minimize the effects of signal noise. Furthermore, the components and / or elements recited in any apparatus claim may be assembled or otherwise operatively configured in various permutations and are therefore not limited to the particular configuration recited in the claims.

[0063] Additionally, functionally equivalent processing steps can be performed in either the time domain or the frequency domain. Thus, although not explicitly stated for each signal processing block in the figures, signal processing may occur in either the time domain, the frequency domain, or a combination thereof. Additionally, although various processing steps are described in general terms of digital signal processing, equivalent steps may be performed using analog signal processing without departing from the scope of this disclosure.

[0064] Benefits, advantages, and solutions to problems have been described above with respect to particular embodiments. However, any benefit, advantage, solution to a problem, or any element that may cause or make more pronounced any particular benefit, advantage, or solution, is not to be construed as a critical, required, or essential feature or component of any or all of the claims.

[0065] The terms "comprise," "comprises," "comprising," "having," "including," "includes," or any variation thereof, are intended to refer to a non-exclusive inclusion, whereby a process, method, article, composition, or apparatus that includes a number of elements not only includes those elements that are recited, but may also include other elements not expressly recited or that are not inherent to such process, method, article, composition, or apparatus. Other combinations and / or modifications of the above-described structures, apparatus, applications, proportions, elements, materials, or components used in the practice of the inventive subject matter, in addition to those not specifically recited, may vary with or otherwise be specifically adapted to particular environments, manufacturing specifications, design parameters, or other operating requirements without departing from the general principles of the invention.

[0066] Although exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms of the present disclosure. 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 present disclosure. Furthermore, features implementing various embodiments may be combined to form further embodiments.

Claims

1. 1. An active noise cancellation (ANC) system, comprising: at least one loudspeaker for projecting an anti-noise sound into the vehicle cabin in response to receiving the anti-noise signal; at least one microphone for providing an error signal indicative of noise in the vehicle cabin and the anti-noise sound; an occupancy controller programmed to modify a transfer function between the at least one microphone and at least one virtual microphone based on an occupancy signal indicating which seat in the vehicle interior is occupied by an occupant; an adaptive filter controller programmed to filter the error signal using the transfer function to obtain an estimated virtual microphone error signal; a controllable filter for generating the anti-noise signal based on the estimated virtual microphone error signal; Equipped with the at least one virtual microphone comprises a first virtual microphone; The occupancy controller is further programmed to modify the transfer function by increasing a gain associated with the first virtual microphone in response to an occupant being in proximity to the first virtual microphone.

2. The ANC system of claim 1 , wherein the at least one virtual microphone further comprises a second virtual microphone spaced apart from the first virtual microphone.

3. The at least one microphone comprises at least two microphones, and the adaptive filter controller further comprises: selecting one of the at least two microphones based on the occupancy signal; filtering the error signal from the selected microphone using the transfer function to obtain the estimated virtual microphone error signal; 2. The ANC system of claim 1, programmed to:

4. The at least one loudspeaker comprises at least two loudspeakers, and the adaptive filter controller further comprises: selecting one of the at least two loudspeakers based on the occupancy signal; and generating the anti-noise signal to be radiated from the selected loudspeaker into the vehicle based on the estimated virtual microphone error signal; 2. The ANC system of claim 1, programmed to:

5. The ANC system of claim 1 , wherein the adaptive filter controller is further programmed to determine a position of the at least one virtual microphone using head tracking techniques.

6. The ANC system of claim 1 , wherein the adaptive filter controller is further programmed to determine a position of the at least one virtual microphone based on a seat position.

7. at least one sensor for providing a non-acoustic noise signal; a second secondary path filter configured to filter the non-acoustic noise signal to obtain a filtered noise signal, the second secondary path filter being defined by a stored transfer characteristic estimating a secondary path between the loudspeaker and the microphone; The ANC system of claim 1 , wherein the adaptive filter controller is further programmed to control the controllable filter based on the filtered noise signal and the estimated virtual microphone error signal.

8. The at least one sensor comprises at least two sensors, and the adaptive filter controller further comprises: and programmed to select one of the at least two sensors based on a coherence of the sensor with at least one of the at least one microphone and the at least one virtual microphone; The ANC system of claim 7 , wherein the second secondary path filter is further configured to filter the non-acoustic noise signal from the selected sensor to obtain a filtered noise signal.

9. 1. A method for controlling a virtual microphone (VM) active noise cancellation (ANC) system, the method comprising: receiving an error signal from a microphone indicative of noise and anti-noise within the vehicle; receiving an occupancy signal from an occupancy detector indicative of which seats within the vehicle are occupied by occupants; modifying a transfer function between the microphone and a virtual microphone based on the occupancy signal; filtering the error signal using the transfer function to obtain an estimated virtual microphone error signal; generating an anti-noise signal based on the estimated virtual microphone error signal, the anti-noise signal being radiated from a loudspeaker into the vehicle; Including, the virtual microphones include a first virtual microphone; Modifying the transfer function further comprises: responsive to an occupant being in proximity to the first virtual microphone, increasing a gain associated with the first virtual microphone.

10. The method of claim 9 , wherein the virtual microphones further include a second virtual microphone spaced apart from the first virtual microphone.

11. The microphone further includes at least two microphones, and the method further comprises: selecting one of the at least two microphones based on the occupancy signal; filtering the error signal from the selected microphone using a secondary path filter to obtain the estimated virtual microphone error signal; 10. The method of claim 9, comprising:

12. The loudspeaker further comprises at least two loudspeakers, and the method further comprises: selecting one of the at least two loudspeakers based on the occupancy signal; and generating the anti-noise signal to be radiated from the selected loudspeaker into the vehicle based on the estimated virtual microphone error signal; 10. The method of claim 9, comprising:

13. The method of claim 9 , further comprising determining the position of the virtual microphone using head tracking techniques.

14. The method of claim 9 , further comprising determining a position of the virtual microphone based on a seat position.

15. 1. An active noise cancellation (ANC) system, comprising: an occupancy controller configured to modify a transfer function between the at least one microphone and the at least one virtual microphone based on an occupancy signal indicative of which seat within the vehicle cabin is occupied by an occupant; an adaptive filter controller configured to filter an error signal indicative of noise and anti-noise sounds in the vehicle cabin using the transfer function to obtain an estimated virtual microphone error signal; a controllable filter for generating an anti-noise signal based on the estimated virtual microphone error signal, providing the anti-noise signal to at least one loudspeaker, and projecting an anti-noise sound into a vehicle cabin; The occupancy controller is further configured to modify the transfer function by increasing a gain associated with a first virtual microphone in response to an occupant being in proximity to the first virtual microphone.

16. Further comprising at least two microphones; The adaptive filter controller further comprises: selecting one of the at least two microphones based on the occupancy signal; filtering the error signal from the selected microphone using the transfer function to obtain the estimated virtual microphone error signal; The ANC system of claim 15 configured to:

17. at least two loudspeakers; The adaptive filter controller further comprises: selecting one of the at least two loudspeakers based on the occupancy signal; and generating the anti-noise signal to be radiated from the selected loudspeaker into the vehicle based on the estimated virtual microphone error signal; The ANC system of claim 15 configured to:

18. The ANC system of claim 15 , wherein the adaptive filter controller is further configured to determine a position of the at least one virtual microphone using head tracking techniques.

19. The ANC system of claim 15 , wherein the adaptive filter controller is further configured to determine a position of the at least one virtual microphone based on a seat position.

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