Active noise cancellation system based on occupancy rate

Abstract

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

Description

Technical Field

[0001] This disclosure relates to an active noise cancellation system, and more specifically to an active noise control framework that controls a virtual microphone based on vehicle occupancy rate. Background Technology

[0002] Active noise cancellation (ANC) systems use feedforward and feedback structures to attenuate unwanted noise, adaptively removing unwanted noise from the listening environment, such as inside a vehicle cabin. ANC systems typically eliminate or reduce unwanted noise by generating cancellation waves that cancel out unwanted audible noise. This cancellation occurs when noise and “anti-noise” are reduced to the sound pressure level (SPL) at a location, where the “anti-noise” is approximately the same amplitude as the noise but out of phase. In a vehicle cabin listening environment, potentially unwanted noise sources include the engine, exhaust system, the interaction between the vehicle tires and the road surface, and / or sound radiated by vibrations from other parts of the vehicle. Therefore, unwanted noise varies with vehicle speed, road conditions, and operating status.

[0003] Road noise cancellation (RNC) systems are specific ANC systems implemented in vehicles to minimize unwanted road noise within the vehicle's cabin. RNC systems use vibration sensors to detect road-induced vibrations generated at the tire-road interface that contribute to undesirable audible road noise. This undesirable road noise is then eliminated or its level reduced by using speakers to generate sound waves that are ideally out of phase and of the same amplitude as the noise to be reduced at the ears of one or more listeners. Eliminating this road noise results in a more pleasant ride for vehicle passengers, and it allows vehicle manufacturers to use lightweight materials, thereby reducing energy consumption and emissions.

[0004] Engine order cancellation (EOC) systems are specific ANC systems implemented in vehicles to minimize unwanted engine noise within the vehicle cabin. EOC systems use non-acoustic signals, such as those from an engine speed sensor, to generate a reference signal representing the engine crankshaft rotational speed (in revolutions per minute (RPM)). This reference signal is used to generate sound waves that are out of phase with the engine noise audible inside the vehicle. Because EOC systems use signals from RPM sensors, they do not require vibration sensors.

[0005] RNC systems are typically designed to eliminate wideband signals, while EOC systems are designed and optimized to eliminate narrowband signals, such as individual engine orders. In-vehicle ANC systems offer both RNC and EOC technologies. Such vehicle-based ANC systems are typically least mean square (LMS) adaptive feedforward systems that continuously adjust a W-type filter based on noise input (e.g., acceleration input from vibration sensors in the RNC system) and signals from physical microphones located at various locations within the vehicle cabin. LMS-based feedforward ANC systems and their corresponding algorithms are characterized by storing the impulse response, or secondary path, between each physical microphone and each noise-generating loudspeaker in the system. The secondary path is the transfer function between the noise-generating loudspeaker and the physical microphone, essentially characterizing how the reactive noise signal transforms into sound radiated from the loudspeaker, propagates through the vehicle cabin to the physical microphone, and becomes the microphone output signal.

[0006] A virtual microphone is a technology in which an ANC system estimates error signals generated by a fictitious or virtual microphone located at a position where no real physical microphone is present, based on error signals received from one or more real physical microphones. This virtual microphone technology improves noise cancellation at the listener's ear, even when no physical microphone is actually located there. Summary of the Invention

[0007] In one embodiment, an active noise cancellation (ANC) system is provided, wherein at least one loudspeaker projects an anti-noise sound within the passenger cabin of a vehicle in response to receiving an anti-noise signal. At least one microphone provides an error signal indicative of noise within the passenger cabin and the anti-noise sound. A load factor controller is programmed to modify a transfer function between the at least one microphone and the at least one virtual microphone based on a load factor signal indicative of the presence of occupants within the passenger cabin. An adaptive filter controller is programmed to filter the error signal using the transfer function to obtain an estimated virtual microphone error signal. A controllable filter generates the anti-noise signal based on the estimated virtual microphone error signal.

[0008] In another embodiment, a method for controlling a virtual microphone (VM) active noise cancellation (ANC) system is provided. An error signal indicative of noise and noise immunity within a vehicle is received from a microphone. An occupancy rate signal indicative of the presence of occupants within the vehicle is received from an occupancy rate detector. A transfer function between the microphone and the virtual microphone is modified based on the occupancy rate signal. The error signal is filtered using the transfer function to obtain an estimated virtual microphone error signal. An noise immunity signal to be radiated from a loudspeaker within 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, wherein an occupancy rate controller is configured to modify a transfer function between at least one microphone and at least one virtual microphone based on the presence of occupants in the vehicle's cabin. An adaptive filter controller is configured to use the transfer function to filter an error signal indicating noise and anti-noise sound within the cabin to obtain an estimated virtual microphone error signal. The ANC system further includes a controllable filter that generates an anti-noise signal based on the estimated virtual microphone error signal and provides the anti-noise signal to at least one loudspeaker to project the anti-noise sound within the vehicle's cabin. Attached Figure Description

[0010] Figure 1 It is an environmental block diagram of a vehicle with an active noise cancellation (ANC) system according to one or more embodiments, the system including road noise cancellation (RNC), a virtual microphone and a occupancy rate detector.

[0011] Figure 2 This is an exemplary schematic diagram showing relevant portions of an RNC system that has been scaled to include the R accelerometer signal and the L speaker signal.

[0012] Figure 3 This is an exemplary schematic block diagram of an ANC system that includes an Engine Order Elimination (EOC) system and an RNC system.

[0013] Figure 4 This is a table showing the different vehicle occupancy rates.

[0014] Figure 5 This is a schematic block diagram representing a virtual microphone ANC system including a load factor controller according to one or more implementation schemes.

[0015] Figure 6 It is a flowchart depicting a method for adjusting virtual microphone parameters based on vehicle occupancy rate in a virtual microphone ANC system, according to one or more embodiments. Detailed Implementation

[0016] As requested, this document discloses detailed embodiments of the present disclosure; however, it should be understood that the disclosed embodiments are merely examples of the present disclosure that may be embodied in various and alternative forms. The accompanying drawings are not necessarily drawn to scale; some features may be enlarged or minimized to show details of specific components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but rather as representative examples only.

[0017] refer to Figure 1A road noise cancellation (RNC) system is shown according to one or more embodiments and is generally represented by the numeral 100. The RNC system 100 is depicted within a vehicle 102 having one or more vibration sensors 104. The vibration sensors 104 are arranged 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 broadband adaptive feedforward and feedback active noise cancellation (ANC) system 106, which generates anti-noise by adaptively filtering signals from the vibration sensors 104 using one or more physical microphones 108. The anti-noise signal can then be played back as sound through one or more loudspeakers or speakers 110. S(z) represents the transfer function between a single speaker 110 and a single microphone 108. Although... Figure 1 A single vibration sensor 104, microphone 108, and speaker 110 are shown for simplicity purposes only; however, it should be noted that a typical RNC system uses multiple vibration sensors 104 (e.g., ten or more), microphones 108 (e.g., four to six), and speakers 110 (e.g., four to eight). According to one or more embodiments, as referenced... Figure 5 As described in detail, the ANC system 106 may also include one or more virtual microphones 112, 113 and one or more occupancy rate detectors 114 for adapting one or more noise immunity signals, which are optimized for occupants in the vehicle 102 at a given time.

[0018] Vibration sensor 104 may include, but is not limited to, accelerometers, force gauges, seismic detectors, linear variable differential transformers, strain gauges, and load sensors. For example, an accelerometer is a device whose output signal amplitude is proportional to the acceleration. Various accelerometers can be used in RNC systems. These accelerometers include those sensitive to vibration in one, two, and three typically orthogonal directions. These multi-axis accelerometers typically have separate electrical outputs (or channels) for sensing vibrations in their X, Y, and Z directions. Therefore, uniaxial and multi-axis accelerometers can be used as vibration sensor 104 to detect the amplitude and phase of acceleration, and can also be used to sense orientation, motion, and vibration.

[0019] Noise and vibration originating from the wheels 116 moving on the road surface 118 can be sensed by one or more vibration sensors 104 mechanically coupled to the suspension system 119 or chassis components of the vehicle 102. The vibration sensors 104 can output a noise signal X(n), which is a vibration signal representing the detected road-induced vibrations. It should be noted that multiple vibration sensors are possible, and their signals can be used individually or in combination. In some embodiments, a microphone can be used instead of a vibration sensor to output a noise signal X(n) indicating the noise generated by the interaction between the wheels 116 and the road surface 118. The noise signal X(n) can be filtered using a modeled transfer characteristic S'(z), which estimates the secondary path (i.e., the transfer function between the noise-canceling loudspeaker 110 and the physical microphone 108) via a secondary path filter 120.

[0020] Road noise originating from the interaction between the wheels 116 and the road surface 118 is also mechanically and / or acoustically transmitted into the passenger cabin and received by one or more microphones 108 within the vehicle 102. One or more microphones 108 may be located, for example, in the roof lining of the vehicle 102, or at some other suitable location to sense the acoustic noise field heard by occupants within the vehicle 102 (such as occupants sitting in the rear seat 125). Road noise originating from the interaction between the road surface 118 and the wheels 116 is transmitted to the microphones 108 according to the transmission characteristics representing the primary path P(z) (i.e., the transfer function between the actual noise source and the physical microphone).

[0021] Microphone 108 can output an error signal e(n), which represents the sound present in the passenger compartment of vehicle 102 as detected by microphone 108, including noise and noise immunity. In RNC system 100, the adaptive transfer characteristic W(z) of controllable filter 126 can be controlled by adaptive filter controller 128, which operates based on the error signal e(n) filtered by filter 120 using the modeled transfer characteristic S'(z) and the noise signal X(n) according to a known least mean square (LMS) algorithm. Controllable filter 126 is commonly referred to as a W-type filter. Noise immunity signal Y(n) can be generated by an adaptive filter formed by controllable filter 126 and adaptive filter controller 128 based on a combination of the identified transfer characteristic W(z) and the vibration signal or vibration signal X(n). The noise immunity signal Y(n) ideally has a waveform such that when played through speaker 110, it generates noise immunity near the occupant's ears and microphone 108, which is substantially out of phase and of the same amplitude as the road noise audible to the occupants of the vehicle compartment. The noise immunity from speaker 110 can be combined with the road noise in the vehicle compartment near microphone 108, resulting in a reduction in the sound pressure level (SPL) caused by the road noise at that location. In some embodiments, the RNC system 100 may receive sensor signals from other acoustic sensors in the cabin, such as acoustic energy sensors, acoustic intensity sensors, or acoustic particle velocity or acceleration sensors, to generate an error signal e(n).

[0022] While vehicle 102 is in operation, processor 130 may collect and optionally process data from one or more vibration sensors 104 and one or more microphones 108 to construct and / or modify a database or mapping containing data and / or parameters used by vehicle 102. The collected data may be stored locally at storage device 132 or in the cloud for future use by vehicle 102. Examples of data types associated with RNC system 100 that may be used for local storage at storage device 132 include, but are not limited to, occupancy rate configuration data related to: secondary paths, transfer function H(z) between physical and virtual microphone positions, preferred physical microphone arrangements, and preferred loudspeaker arrangements. In one or more embodiments, processor 130 and storage device 132 may be integrated with one or more RNC system controllers, such as adaptive filter controller 128.

[0023] As previously described, a typical RNC system can use several vibration sensors, microphones, and speakers to sense the structurally propagated vibration behavior of a vehicle and generate noise immunity. The vibration sensors can be multi-axis accelerometers with multiple output channels. For example, triaxial accelerometers typically have separate electrical outputs for sensing vibrations in their X, Y, and Z directions. A typical configuration of an RNC system may have, for example, six physical microphones, six speakers, and twelve acceleration signal channels from four triaxial accelerometers or six biaxial accelerometers. Therefore, the RNC system will also include multiple S'(z) filters (i.e., secondary path filters 120) and multiple W(z) filters (i.e., controllable filters 126).

[0024] Figure 1 The simplified RNC system diagram shown illustrates a secondary path, denoted by S(z), between loudspeaker 110 and microphone 108. As previously mentioned, RNC systems typically have multiple loudspeakers, microphones, and vibration sensors. Therefore, a six-loudspeaker, six-microphone RNC system would have a total of thirty-six secondary paths (i.e., 6×6). Correspondingly, a six-loudspeaker, six-microphone RNC system could also have thirty-six S'(z) filters (i.e., secondary path filters 120) that estimate the transfer function of each secondary path. Figure 1 As shown, the RNC system will also have a W(z) filter (i.e., a controllable filter 126) between each noise signal X(n) from the vibration sensor (i.e., accelerometer) 104 and each speaker 110. Therefore, a twelve-accelerometer, six-speaker RNC system can have seventy-two W(z) filters. The relationship between the number of accelerometer signals, speakers, and W(z) filters is shown in... Figure 2 middle.

[0025] Figure 2 This is an exemplary schematic diagram showing relevant portions of an RNC system 200, which is scaled to include R accelerometer signals [X1(n), X2(n), ... Xn] from accelerometer 204. R [Y1(n), Y2(n), ..., Yn(n)] and L loudspeaker signals [Y1(n), Y2(n), ..., Yn(n)] from loudspeaker 210. L(n)]. Therefore, the RNC system 200 may include R*L controllable filters (or W-type filters) 226 between each of the accelerometer signals and each of the speakers. As an example, an RNC system with twelve accelerometer outputs (i.e., R = 12) may employ six biaxial accelerometers or four triaxial accelerometers. Thus, in the same example, a vehicle with six speakers (i.e., L = 6) for reproducing noise immunity may use a total of seventy-two W-type filters. At each of the L speakers, the outputs of the R W-type filters are summed to generate a speaker noise immunity signal Y(n). 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-type filters are summed to form an electro-noise immunity signal y(n), which is fed to an amplifier to generate an amplified noise immunity signal Y(n) sent to the speaker.

[0026] Figure 1 The ANC system 106 shown may also include an Engine Order Cancellation (EOC) system. As described above, EOC technology uses a non-acoustic signal, such as an engine speed signal representing the engine crankshaft speed, as a reference to generate a sound that is phase-opposite to the engine noise audible inside the vehicle. The EOC system can utilize the engine speed signal to guide the generation of an engine order signal that is the same in frequency as the engine order to be cancelled and adaptively filter it to form an anti-noise signal, thereby utilizing a narrowband feedforward ANC framework to generate anti-noise. After being transmitted from the anti-noise source to the listening position or physical microphone via a secondary path, the anti-noise ideally has the same amplitude but opposite phase as the combined sound generated by the engine and exhaust pipe after filtering via the primary path, which extends from the engine to the listening position and from the exhaust pipe outlet to the listening position or physical or virtual microphone position. Therefore, at the location where the physical microphone is located in the vehicle compartment (i.e., most likely at or near the listening position), the superposition of engine order noise and noise immunity will ideally become zero, such that the acoustic error signal received by the physical microphone will only record sounds other than one or more engine orders generated by the engine and exhaust (ideally eliminated).

[0027] Typically, a non-acoustic sensor, such as an engine speed sensor, is used as a reference. The engine speed sensor can be, for example, a Hall effect sensor placed adjacent to a rotating steel disc. Other detection principles can be employed, such as optical or inductive sensors. 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 cancellation signal, which is generated by one or more narrowband adaptive feedforward LMS blocks forming the EOC system.

[0028] Figure 3 This 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-type filter 326, an adaptive filter controller 328, a secondary path filter 320, and a loudspeaker 310, which operate in accordance with the operation of the vibration sensor 104, physical microphone 108, W-type filter 126, adaptive filter controller 128, secondary path filter 120, and loudspeaker 110, respectively.

[0029] The EOC system 340 may include an engine speed sensor 342 that provides an engine speed signal 344 (e.g., a square wave signal) indicating the rotation of the engine crankshaft or other rotating shafts (such as drive shafts, half-shafts, or other shafts whose rotational rate is aligned with vibrations coupled to vehicle components that cause noise in the cabin). In some embodiments, the engine speed signal 344 may be obtained from a vehicle network bus (not shown). Since the radiated engine order is proportional to the crankshaft RPM, the engine speed signal 344 represents the frequency generated by the engine and exhaust system. Therefore, the signal from the engine speed sensor 342 can be used to generate a reference engine order signal corresponding to each of the vehicle's engine orders. Thus, the engine speed signal 344 can be used in conjunction with a lookup table 346 of engine speed (RPM) versus engine order frequencies, which provides a list of the engine orders radiated at each engine speed. An adaptive filter controller 328 may take the engine speed (RPM) as input and generate a sine wave for each order based on this lookup table 346.

[0030] The frequency of a given engine order at a sensed engine speed (RPM), retrieved from lookup table 346, can be supplied to frequency generator 348 to generate a sine wave at the given frequency. This sine wave represents a noise signal X(n) indicating engine order noise for the given engine order. Similar to RNC system 300, this noise signal X(n) from frequency generator 348 can be sent to adaptive controllable filter 326 or W-type filter, which provides a corresponding anti-noise signal Y(n) to loudspeaker 310. As shown, the various components of this narrowband EOC system 340 can be the same as those of the wideband RNC system 300, including physical microphone 308, adaptive filter controller 328, and secondary path filter 320. The anti-noise signal Y(n) broadcast by loudspeaker 310 generates anti-noise that is substantially out of phase with the actual engine order at the listener's ear position, which can be very close to physical microphone 308, thereby reducing the sound amplitude of the engine order. Since the engine order noise is narrowband, the error signal e(n) can be filtered by the bandpass filter 350 before entering the LMS-based adaptive filter controller 328. In one embodiment, the correct operation of the LMS adaptive filter controller 328 is achieved when 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 multiple frequency generators 348 for generating a noise signal X(n) for each engine order based on the engine speed signal (RPM) 344. As an example, Figure 3 A two-order EOC system with two such frequency generators is shown, which generate noise signals (e.g., X1(n), X2(n), etc.) for each engine order based on engine speed. Since the frequencies of the two engine orders are different, bandpass filters 350 (labeled BPF and BPF2) have different high-pass and low-pass filter angular frequencies. The number of frequency generators and corresponding noise cancellation components will vary based on the number of engine orders to be cancelled for a particular engine of the vehicle. When the two-order EOC system 340 is combined with the RNC system 300 to form the ANC system 306, the anti-noise signal Y(n) output from the three controllable filters 326 is summed and sent as a speaker signal S(n) to the speaker 310. 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 can lead to degradation in noise cancellation performance, noise gain, or practical instability. As previously described, the secondary path is the transfer function between the noise-generating loudspeaker and the physical microphone. Therefore, it essentially characterizes how the reactive noise signal Y(n) becomes the sound radiated from the loudspeaker, propagates through the vehicle cabin to the physical microphone, and becomes part of the microphone output or error signal e(n) in the ANC system. When the vehicle becomes substantially different from the reference vehicle or system in terms of geometry, number of passengers, luggage loading, etc., the actual secondary path S(z) can deviate from the stored secondary path model S'(z), which is typically measured on a "golden system" by trained engineers. In one implementation, a vehicle with occupancy rate detection can select an appropriate set of secondary paths from a pre-determined stored database to improve the performance of the noise cancellation system.

[0033] An ANC system generates noise immunity that is ideally phase-opposite and amplitude-same as the noise to be reduced at the ears of one or more listeners. Existing ANC systems typically generate a noise reduction zone (“silent zone”) centered on the location of one or more physical microphones. The size of the silent zone is approximately one-tenth of the wavelength of the sound wave, resulting in a small silent zone with a reduced size to increase the frequency. If only one physical microphone is used in a vehicle application, a steep performance gradient will exist as people move their ears away from the microphone, particularly when the ears are moved away from a distance greater than one-tenth of the wavelength. Additionally, for a system including only one physical microphone, it is likely that the sound pressure level will increase in all other locations in the vehicle. To avoid this “noise boost” at the location of the first or second vehicle occupant, four or six physical microphones can be used, allowing the active system to reduce the noise field more uniformly throughout the vehicle. For maximum perceived noise cancellation, the physical microphones would ideally be positioned at the occupant’s ear location. However, in many practical situations, the physical microphones cannot be placed close to the ears of all vehicle passengers. This is due to vehicle packaging limitations, such as convertible roofs, canopy roofs, and the absence of seat-mounted microphones, all of which can make it difficult to achieve maximum noise reduction at the location of the vehicle's passengers' ears when it is most needed.

[0034] Re-reference Figure 1 Vehicle 102 includes a physical microphone 108 located within the roof liner. The physical microphone 108 is not adjacent to the ears of an occupant seated in the rear seat 125. However, the ANC system 106 includes a virtual microphone 112 adjacent to the ears of an occupant seated in the rear seat 125.

[0035] A virtual microphone is a technology in which an ANC system estimates an error signal generated by a fictitious or virtual microphone at a location where no real physical microphone is present, based on error signals received from one or more real physical microphones. This virtual microphone technology improves noise cancellation at the passenger's ear location, even when no physical microphone is actually located there. An added benefit is that this virtual microphone technology provides a flexible solution for the physical microphone installation location. Compared to conventional non-virtual noise cancellation algorithms, virtual microphone algorithms utilize the estimated virtual signal as the error signal e. v (n). Based on virtual error signal estimation, the virtual microphone algorithm adapts the W-type filter based on the estimated virtual error signal rather than the physical error signal. Therefore, the noise cancellation system performance is maximized at the locations of these virtual microphones, ideally close to the listener's actual ear position, rather than at the location of the physical microphones, which can be located far from the listener's ear, such as on the vehicle's headliner. Vehicles with headrest-mounted microphones can benefit from virtual microphone technology because the virtual microphones can be closer to the occupant's ear than headrest-mounted microphones.

[0036] refer to Figure 4 Vehicles can have a variety of different occupancy configurations, making it difficult for ANC systems to determine the position of passengers' ears. Figure 4 Table 400 shows different occupancy configurations for a vehicle with five seats: driver's seat (D), front passenger seat (FP), first rear passenger seat (RP1), second rear passenger seat (RP2), and third rear passenger seat (RP3). Such a vehicle may include a first configuration (1A) with a single 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 fifth configuration (5A) with five occupants. In the first configuration (1A), the driver's seat (D) is occupied (O), but not all passenger seats are occupied (X). In the first second configuration 2A... Figure 4 In the configuration shown, the driver's seat (D) and the front passenger seat (FP) are occupied. In the third second configuration 2C (not shown), the driver's seat (D) and the second rear passenger seat (RP2) are occupied. The virtual microphone located at the ear of the passenger sitting in the front passenger seat (FP) is not optimal for the passenger sitting in the second rear passenger seat (RP2), and vice versa.

[0037] An ANC system can include many speakers that radiate noise immunity to passengers; however, 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 limitation of algorithm output channels, only a limited number of noise immunity signals can be generated at a time. Speakers very close to the front passenger radiate noise immunity more effectively to the front passenger, resulting in superior noise cancellation compared to using speakers at a greater distance. At this occupancy rate, more front-seat speakers can be used to radiate noise immunity, and fewer speakers closer to the empty rear seats can be used.

[0038] Additionally, an ANC system may include numerous physical microphones installed in the vehicle; however, the number of physical microphone channels that can be used simultaneously may be limited due to ADC or amplifier / algorithm / DSP chip MIPS limitations or other design constraints. When only the front seats are occupied, additional microphones near the front passengers can be selected to output their noise signals e(n) to the noise cancellation algorithm, replacing one or more microphones closer to the unoccupied (rear) seats, in an effort to provide optimal noise cancellation for the occupied seats.

[0039] Similarly, although many accelerometer (noise) reference channels may exist, noise cancellation systems can only utilize a smaller number of channels simultaneously due to hardware input or MIPS limitations. When only the front seat is occupied, an additional reference signal from the front of the vehicle can be used instead of one or more reference signals originating from the rear of the vehicle. In one or more embodiments, a reference signal from a sensor with the highest coherence to the physical or virtual microphone closest to the occupied seat is selected, regardless of their proximity to the occupied seat.

[0040] Re-reference Figure 1 Vehicle 102 includes an occupancy rate detector 114 that provides an occupancy rate signal (Occ) indicating whether the front seat 124 is occupied. Although Figure 1The diagram shows one occupancy rate detector 114, but the ANC system 106 may include one occupancy rate detector 114 for each seat or a number of other occupancy rate detectors. The occupancy rate detector 114 may include multiple sensors and / or technologies for detecting thermal signatures, such as seatbelt sensors, seat sensors, proximity sensors, load sensors, motion sensors, cameras with machine vision systems, cameras with facial recognition or infrared (IR) imaging capabilities, passive infrared (PIR) sensors, or IR or near-IR sensors. In one embodiment, the occupancy rate detector 114 may include a microphone or microphone array adapted to act as an occupancy rate sensor and optionally coupled to an adaptive beamformer. The ANC system 106 may allow a user to manually input occupancy rate information via a user interface such as buttons or a touchscreen option.

[0041] The ANC system 106 can use various methods, including sensors, sensor arrays, sensor fusion, and speech recognition, to detect which vehicle seats are occupied. The ANC system 106 then uses a combination of physical microphones, virtual microphones, accelerometer sensors, physical and virtual secondary paths, transfer functions, tuning parameters, and speakers configured for a given occupancy rate to select the optimal noise cancellation tuning. In one embodiment, the ANC system 106 includes a camera (not shown) or other device that uses head-tracking technology to determine the virtual microphone position to determine the location of the occupant's ear canal opening.

[0042] An ANC system achieves optimal performance when the position of each virtual microphone in the occupant's ear in 3D space aligns with that of the physical microphone. When the virtual microphone is positioned closer to the ear than the physical microphone, the ANC system achieves improved performance compared to traditional non-virtual microphone techniques. Other techniques for selecting virtual microphone positions include using a seat position encoder. The ANC system can use data from the current seat position to estimate the position of the seat occupant's ears in three dimensions to select the virtual microphone position closest to the occupant's ear, for example, by selecting a low virtual microphone position for a forward-facing seat position and a high virtual microphone position for a rearward-facing seat position. The virtual microphone positions can be predetermined by the ANC system tuning engineer during ANC system tuning; therefore, the selection of virtual microphone positions involves determining which virtual microphones are closest to the ear in 3D space.

[0043] Figure 5 This is a schematic block diagram of a vehicle-based virtual microphone (VM) ANC system 506, illustrating many key ANC system parameters that can be used to estimate the virtual microphone error signal based on vehicle occupancy rate to optimize ANC system performance. For ease of illustration, Figure 5The VM ANC system 506 shown is illustrated as having components and features of an RNC system 500 and an EOC system 540. Therefore, the VM ANC system 506 is a schematic representation of an RNC and / or EOC system, such as a combination of... Figures 1 to 3 The described features include additional system components of the VM ANC system 506, including a virtual microphone 512 and a load factor 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-type filter 526, an adaptive filter controller 528, a virtual secondary path filter 520, and a loudspeaker 510, respectively, operating in accordance with the aforementioned vibration sensor 104, physical microphone 108, W-type filter 126, adaptive filter controller 128, secondary path filter 120, and loudspeaker 110. Figure 5 For illustrative purposes, the primary path P(z) and secondary path S(z) are also shown in boxes, as shown in reference [reference]. Figure 1 As stated above.

[0044] The physical microphone 508 provides an error signal e that includes all sounds present at its location. p (n), such as interference signals d intended to be eliminated. p (n), which includes road noise, engine and exhaust noise, plus noise immunity y from speaker 510. p (n), and any external sounds at the microphone location.

[0045] Virtual microphone 512 refers to a microphone located at the virtual microphone position, which will similarly sense all sounds at its position, such as interference signals d to be eliminated. v (n), which includes road noise, engine and exhaust noise, plus noise immunity y from speaker 510. v (n) and external sounds. Typically, there are multiple physical microphone locations and multiple virtual microphone locations. It should be noted that when operating a noise cancellation system, no actual microphone is installed at the virtual microphone locations. Therefore, using virtual microphone technology, the pressure at the virtual microphone locations is estimated based on the pressure at the physical microphone locations to form an estimated error signal e'. v (n).

[0046] The physical microphone 508 senses the noise d from the noise source 542 at its location after propagation along the primary path P(z) 544. p (n), and senses the noise immunity y from the speaker 510 at its location after propagation along the secondary path Se(z)546. p (n). The physical microphone 508 provides the physical error signal e.p (n), as shown in Equation 1:

[0047] e p (n)=d p (n)+y p (n) (1)

[0048] At box 548, VM ANC system 506 estimates the interference noise d' to be eliminated at the physical microphone location. p (n). The VM ANC system 506 obtains the physical error signal e p (n) minus the noise immunity y' at the physical microphone location p The estimated value of (n) is used to estimate the interference noise d' at the physical microphone location. p (n), as shown in Equation 2:

[0049] d′ p (n)=e p (n)-y′ p (n) ( 2 )

[0050] The VM ANC system 506 then uses the estimated interference noise d' at the physical microphone location at box 550. p (n) is convolved with the transfer function H(z)550 to estimate the interference noise d' to be eliminated at the virtual microphone location. v (n), where the transfer function lies between the physical microphone position and the virtual microphone position. The VM ANC system 506 includes an occupancy rate controller 552 that receives an occupancy rate signal (Occ) from an occupancy rate detector 514 and adjusts tuning parameters such as: H-type filter, secondary path, primary error signal, virtual error signal, speaker noise signal, and reference noise signal based on the vehicle's current occupancy rate configuration. For example, gain can be added to a physical or virtual error signal located near an occupied seat, relative to a physical or virtual error signal from near an unoccupied seat. Similarly, the VM ANC system 506 can add attenuation to physical or virtual error signals near one or more unoccupied seats. This will cause the LMS system 528 to adjust the W-type filter 526 to increase noise cancellation in the vehicle interior area near occupied seats.

[0051] At box 554, the VM ANC system 506 will eliminate the estimated interference noise d' to be removed at the virtual microphone location. v (n) and the noise immunity y' at this location v The estimated values ​​of (n) are summed to estimate the virtual microphone error signal e' that will appear at the virtual microphone position. v (n), as shown in Equation 3:

[0052] e′ v (n)=d′ v (n)+y′ v (n) (3)

[0053] By combining equations 1, 2, and 3, an estimate of the virtual error microphone signal is created based on the physical error signal, the secondary paths of the physical and virtual microphones, and the transfer function between the physical and virtual positions.

[0054] and Figure 1 Similarly, a noise signal X(n) from a noise input such as vibration sensor 504 can be used by virtual secondary path filter 520 with the modeled transfer characteristics S' using the stored estimate of the virtual secondary path as described above. v (z) is filtered to obtain the filtered noise signal X'(n). Furthermore, the transfer characteristic W(z) of the controllable filter 526 (e.g., a W-type filter) can be controlled by an LMS adaptive filter controller (or simply an LMS controller) 528 to provide adaptive filtering. The LMS adaptive filter controller 528 receives the filtered noise signal X'(n) and the estimated virtual error signal e'. v (n) The W-type filter is adjusted to produce 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).

[0055] Similar to Figure 2 The VM ANC system 506 is scaled to include R accelerometer signals, L loudspeaker or megaphone signals, and M microphone error signals. Therefore, the VM ANC system 506 may include R*L controllable filters (or W-type filters) 526 and L*M noise immunity signals.

[0056] Figure 6 This is a flowchart depicting a method 600 for adjusting virtual microphone system parameters based on vehicle occupancy rate in a virtual microphone ANC system, according to one or more embodiments of this disclosure. The various steps of the disclosed method may be performed individually by an adaptive filter controller 528, or in combination with other components of the VM ANC system 506.

[0057] At step 602, the VM ANC system 506 receives input from the occupancy rate detector 514 indicating which vehicle seats are occupied. Then, at step 604, the occupancy rate controller 552 determines the occupancy rate configuration based on the input, for example... Figure 4One of the configurations shown. At step 606, VM ANC system 506 compares the load factor configuration with the last saved load factor configuration to determine if the load factor configuration has changed. If the configuration has not changed, VM ANC system 506 returns to step 602. If the configuration has changed, VM ANC system 506 continues to step 608 and adjusts one or more VM ANC system parameters.

[0058] At step 608, the VM ANC system 506 adjusts the noise immunity signal Y(n) provided to one or more speakers 510 based on the current load factor configuration. The load factor controller 552 may include predetermined stored data indicating optimal transfer function parameters, such as H-type filters, for each load factor configuration based on the hardware and software limitations of 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 load factor configuration, and the VM ANC system 506 selects the complete set of parameters from the database at step 608. In another embodiment, the database stores only a subset of the aforementioned VM ANC system parameters.

[0059] Many parameters in VM ANC system 506 are linked together, and therefore VM ANC system 506 can change multiple parameters sequentially before and after step 608. In one implementation, if VM ANC system 506 modifies the configuration of virtual microphone 512, it also modifies the virtual secondary path S' based on the modified configuration. v (z)520 and microphone transfer function H(z)550. In another implementation, if the VM ANC system 506 modifies the configuration of the physical microphone 508, it also modifies the physical secondary path S' based on the modified configuration. p (z)549 and microphone transfer function H(z)550. In another embodiment, VM ANC system 506 uses the same physical error signal e p Multiple copies of (n) are used to replace certain 'deactivation' error signals. In another implementation, if the VM ANC system 506 modifies the configuration of the speaker 510, it also modifies the physical secondary path S' based on the modified configuration. p (z)549 and virtual secondary path S' v(z)520. In one implementation, if the VM ANC system 506 modifies the configuration of the noise signal X(n), it also resets or modifies the W-type filter 526 based on the modified configuration.

[0060] In one or more embodiments, when the vehicle is in an unoccupied configuration, the VM ANC system 506 selects more virtual microphones near the occupied seats to improve noise cancellation in the occupied seats, in part, by providing noise cancellation in the unoccupied areas of the vehicle without over-constraining the system. In one embodiment, more than one virtual microphone location is selected around each seat headrest, and a relevant transfer function S' is stored for each speaker and physical microphone in the system. v (z) and H(z). In an implementation with only one occupant, all eight virtual microphone signals e' input to LMS block 528 v (n) are all very close to the driver, at a position around the occupant's head.

[0061] Although the VM ANC system 506 is described with reference to a virtual microphone, other implementations of the ANC system include remote microphones (RM) to provide an RM ANC system. The remote microphone differs from the virtual microphone in the value of its transfer function H(z). The VM ANC system 506 includes an H(z) value of unity or one, meaning that any difference in the interfering signal to be eliminated between the physical and virtual locations is simply ignored. In some literature, the RM ANC system includes a transfer function H(z) that is not equal to one, meaning that there is a difference in the interfering signal to be eliminated between the physical and virtual locations. All the various implementations described herein using the term virtual microphone system or technology are applicable to remote microphone technology, with one variation being the value of H(z).

[0062] Although the ANC system is described with reference to a vehicle, the techniques described herein are also applicable to non-vehicle applications. For example, a room may have fixed seats defining the listening position, where reference sensors, error sensors, speakers, and an LMS adaptive system are used to silence interfering sounds. It should be noted that the interfering noise to be eliminated may be of different types, such as HVAC noise or noise from adjacent rooms or spaces. Furthermore, the room may have occupants whose positions change over time, and the seat sensors or head-tracking techniques described herein must then be relied upon to determine the position of one or more listeners, enabling the selection of the 3D position of the virtual microphone.

[0063] although Figure 1 , Figure 3 and Figure 5LMS-based adaptive filter controllers 128, 328, and 528 are shown respectively, but other methods and apparatuses are possible for tuning or creating optimal controllable W-type filters 126, 326, and 526. For example, in one or more embodiments, a neural network may be used instead of the LMS adaptive filter controller to create and optimize the W-type filter. In other embodiments, machine learning or artificial intelligence may be used instead of the LMS adaptive filter controller to create the optimal W-type filter.

[0064] Any or more of the controllers or devices described herein include computer-executable instructions that can be compiled or interpreted from a computer program created using various programming languages ​​and / or techniques. Typically, a processor (such as a microprocessor) receives and executes instructions, for example, from memory, a computer-readable medium, etc. Processing units include non-transitory computer-readable storage media capable of executing the instructions of a software program. Computer-readable storage media can be, but is not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination thereof.

[0065] For example, the steps recited in any method or process claim can be performed in any order and are not limited to the specific order presented in the claim. Equations can be implemented using filters to minimize the effects of signal noise. Additionally, the components and / or elements listed in any device claim can be assembled or otherwise operatively configured in various arrangements and are therefore not limited to the specific configurations listed in the claim.

[0066] Furthermore, functionally equivalent processing steps can be performed in the time domain or the frequency domain. Therefore, although not explicitly illustrated for each signal processing block in the figures, signal processing can occur in the time domain, the frequency domain, or a combination thereof. Moreover, although the various processing steps are explained in typical digital signal processing terminology, equivalent steps can be performed using analog signal processing without departing from the scope of this disclosure.

[0067] The benefits, advantages, and solutions to the problems have been described above with reference to specific embodiments. However, any benefit, advantage, solution to the problem, and any element that makes any particular benefit, advantage, or solution present or more significant should not be construed as a key, essential, or necessary feature or component of any or all claims.

[0068] The terms “comprising,” “including,” “covering,” “having,” “containing,” or any variation thereof are intended to refer to a non-exclusive inclusion, such that a process, method, article, composition, or apparatus that comprises a list of elements includes not only those elements described but also other elements not expressly listed or inherent to such processes, methods, articles, compositions, or apparatus. Other combinations and / or modifications of the above-described structures, arrangements, applications, proportions, elements, materials, or components used in the practice of the subject matter of this invention may also be altered or otherwise adapted specifically to particular environments, manufacturing specifications, design parameters, or other operational requirements without departing from their general principles.

[0069] While exemplary embodiments have been described above, they are not intended to describe all possible forms of this disclosure. Rather, the terms used herein are descriptive rather than limiting, and it should be understood that various changes may be made without departing from the spirit and scope of this disclosure. Additionally, features of various implementation embodiments may be combined to form other embodiments.

Claims

1. An active noise cancellation (ANC) system, comprising: At least one loudspeaker, the at least one loudspeaker being used to project anti-noise sound into the passenger compartment of the vehicle in response to receiving an anti-noise signal; At least one microphone, the at least one microphone being used to provide an error signal indicating the noise within the cabin and the noise-resistant sound; A load factor controller, the load factor controller being programmed to modify the transfer function between the at least one microphone and the at least one virtual microphone based on a load factor signal indicating the presence of occupants in the cabin; An adaptive filter controller, the adaptive filter controller being programmed to filter the error signal using the transfer function to obtain an estimated virtual microphone error signal; as well as A controllable filter is used to generate the noise-resistant signal based on the estimated virtual microphone error signal; The at least one virtual microphone includes a first virtual microphone and a second virtual microphone spaced apart from the first virtual microphone; and The occupancy rate controller is further programmed to modify the transfer function by increasing the gain associated with the first virtual microphone in response to an occupant's proximity to the first virtual microphone.

2. The ANC system of claim 1, wherein the at least one microphone comprises at least two microphones, and wherein the adaptive filter controller is further programmed to: Select one of the at least two microphones based on the load factor signal; and The error signal from the selected microphone is filtered using the transfer function to obtain the estimated virtual microphone error signal.

3. The ANC system of claim 1, wherein the at least one loudspeaker comprises at least two loudspeakers, and wherein the adaptive filter controller is further programmed to: Select one of the at least two loudspeakers based on the load factor signal; and Based on the estimated virtual microphone error signal, the noise immunity signal to be radiated from the selected loudspeaker inside the vehicle is generated.

4. The ANC system of claim 1, wherein the adaptive filter controller is further programmed to use head tracking technology to determine the position of the at least one virtual microphone.

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

6. The ANC system of claim 1, further comprising: At least one sensor, said at least one sensor being used to provide a non-acoustic noise signal; A second-stage path filter, configured to filter the non-acoustic noise signal to obtain a filtered noise signal, is defined by the stored transfer characteristics of the estimated secondary path between the loudspeaker and the microphone; and 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.

7. The ANC system of claim 6, wherein the at least one sensor comprises at least two sensors, and wherein the adaptive filter controller is further programmed to: One of the at least two sensors is selected based on the coherence of the sensor with at least one of the at least one microphone and the at least one virtual microphone; and The second-stage path filter is further configured to filter the non-acoustic noise signal from the selected sensor to obtain a filtered noise signal.

8. A method for controlling a virtual microphone active noise cancellation (ANC) system, the method comprising: Receive error signals from the microphone indicating noise levels and noise immunity within the vehicle; Receive a load factor signal indicating the presence of occupants in the vehicle from the load factor detector; Modify the transfer function between the microphone and the virtual microphone based on the load factor signal; The error signal is filtered using the transfer function to obtain an estimated virtual microphone error signal; as well as Based on the estimated virtual microphone error signal, an anti-noise signal to be radiated from the loudspeaker inside the vehicle is generated; The virtual microphone includes a first virtual microphone and a second virtual microphone spaced apart from the first virtual microphone, and modifying the transfer function further includes: The gain associated with the first virtual microphone is increased in response to the presence of an occupant in the vicinity of the first virtual microphone.

9. The method of claim 8, wherein the microphone further comprises at least two microphones, and wherein the method further comprises: Select one of the at least two microphones based on the load factor signal; as well as The error signal from the selected microphone is filtered using the transfer function to obtain the estimated virtual microphone error signal.

10. The method of claim 8, wherein the loudspeaker further comprises at least two loudspeakers, and wherein the method further comprises: Select one of the at least two loudspeakers based on the load factor signal; as well as Based on the estimated virtual microphone error signal, the noise immunity signal to be radiated from the selected loudspeaker inside the vehicle is generated.

11. The method of claim 8, further comprising using head tracking technology to determine the position of the virtual microphone.

12. The method of claim 8, further comprising determining the position of the virtual microphone based on the seat position.

13. An active noise cancellation (ANC) system, comprising: A load factor controller, configured to modify the transfer function between at least one microphone and at least one virtual microphone based on the presence of occupants in the passenger cabin of the vehicle. An adaptive filter controller is configured to use the transfer function to filter an error signal indicating noise and noise immunity within the cabin to obtain an estimated virtual microphone error signal. as well as A controllable filter is provided for generating an anti-noise signal based on the estimated virtual microphone error signal and providing the anti-noise signal to at least one loudspeaker to project anti-noise sound into the passenger cabin of the vehicle. The virtual microphone includes a first virtual microphone and a second virtual microphone spaced apart from the first virtual microphone, wherein the adaptive filter controller is further configured to modify the transfer function by increasing the gain associated with the first virtual microphone in response to an occupant's proximity to the first virtual microphone.

14. The ANC system of claim 13, further comprising: At least two microphones; and The adaptive filter controller is further configured to: Based on the presence of the occupant, one of the at least two microphones is selected; and The error signal from the selected microphone is filtered using the transfer function to obtain the estimated virtual microphone error signal.

15. The ANC system of claim 13, further comprising: At least two loudspeakers; and The adaptive filter controller is further configured to: Based on the presence of the occupants, one of the at least two loudspeakers is selected; and Based on the estimated virtual microphone error signal, the noise immunity signal to be radiated from the selected loudspeaker inside the vehicle is generated.

16. The ANC system of claim 13, wherein the adaptive filter controller is further configured to use head tracking technology to determine the position of the at least one virtual microphone.

17. The ANC system of claim 13, wherein the adaptive filter controller is further configured to determine the position of the at least one virtual microphone based on the seating position.

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