Patent Description:
Active noise control (ANC) systems are oftentimes employed to suppress unwanted acoustic noise signals with noise-cancelling signals. Ideally, a noise-cancelling signal has the same amplitude and frequency components as the acoustic noise signal to be suppressed, but with a phase shift of <NUM>° with respect to the noise signal. The noise-cancelling signal interferes destructively with the noise signal, and thus eliminates or damps the unwanted acoustic noise signal in a particular location.

ANC systems are commonly employed in motor vehicles, aircraft, and headphones, to enhance in-vehicle audio entertainment, facilitate conversation, and reduce discomfort associated with high volume ambient noise. The degree of noise reduction imparted by such systems is strongly dependent on the coherence between the correcting sound signal and the reference signal used to generate the correcting sound signal. To generate a noise-cancelling signal having high coherence with the reference signal, a given ANC system typically includes a noise sensor, such as an accelerometer or other non-acoustic sensor, directly mounted on a vibrating structure that generates unwanted noise.

<CIT> discusses an earphone adapted to fit within a human ear that generates sound via the propagation of one or more diaphragms aligned to fit the structure and shape of the earphone. The earphone allows ambient sound to pass through the device in order to be heard by the user. Additionally, the earphone can be used in conjunction with a buffering device in communication with a source of non-repetitive, unpredictable sounds in order to characterize and negate those noises.

<CIT> discusses a noise mitigation seating system to detect ambient noise from the surrounding area as perceived inside a vehicle cabin. <CIT> relates to a noise cancellation system including a digital microphone to detect ambient noise, a sigma delta modulator coupled to an output of the digital microphone. <CIT> discloses active noise cancellation based on sound detected by a microphone installed in a vehicular cabin and generation of an anti-phase waveform and an adaptive filter is used in order to reduce remaining noise. Wanted signals are enhanced by means of sound extracting filters.

However, for noise sources that are spatially uncorrelated, i.e., where the noise source is not tied to a vibrating structure, achieving adequate correlation using non-acoustic sensors is problematic, because the noise sources are not a vibrating structures on which such sensors can be mounted. For example, tire noise or the turbulent boundary layer outside a moving vehicle are not generated by the vibrations of a physical structure, and therefore cannot be directly measured with an accelerometer. Consequently, ANC systems are not very effective in reducing noise generated by noise sources such as these that are spatially uncorrelated.

Accordingly, what would be useful is an ANC system that can reduce noise generated by noise sources that are not vibrating structures.

The various embodiments set forth a method for actively controlling noise according to claim <NUM>, an active noise control system according to claim <NUM>, and a non-transitory computer readable medium storing instructions according to claim <NUM>.

At least one advantage of the disclosed embodiments is that noise sources that cannot be individually measured, for example with an accelerometer mounted to a vibrating structure, can still be identified and actively cancelled.

So that the manner in which the above recited features of the various embodiments can be understood in detail, a more particular description of the various embodiments, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments and are therefore not to be considered limiting of its scope, for the various embodiments may admit to other equally effective embodiments, as defined in the appended claims.

For clarity, identical reference numbers have been used, where applicable, to designate identical elements that are common between figures. It is contemplated that features of one embodiment may be incorporated in other embodiments without further recitation, as defined in the appended claims.

<FIG> is a block diagram of an active noise cancellation (ANC) system <NUM>, according to various embodiments. ANC system <NUM> is a feed-forward active noise-cancellation system configured for use in a motor-vehicle or aircraft. In examples not forming part of the invention, it may be incorporated into any other environment, such as a room in a home, a headphone system, etc. As shown, ANC system <NUM> includes a source separation processor <NUM>, a controller <NUM>, an acoustic actuator <NUM>, a reference microphone <NUM> coupled to the source separation processor <NUM>, and an error microphone <NUM> coupled to the controller <NUM> and disposed in a listening location <NUM>. Listening location <NUM> is the area targeted for maximum noise reduction by ANC system <NUM>, such as a rear passenger area in a motor vehicle equipped with audio entertainment, or a region that includes the head of a passenger or driver.

In some embodiments, ANC system <NUM> may configured as a subsystem of a vehicle infotainment system associated with the vehicle and share computational resources therewith. In other embodiments, ANC system <NUM> may be implemented as a stand-alone or add-on feature, part of the original equipment manufacturer (OEM) controls of the vehicle, or a combination of both.

Source separation processor <NUM> may be any suitable processor, such as a CPU, a graphics processing unit (GPU), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), any other type of processing device, or a combination of different processing devices. In general, source separation processor <NUM> may be any technically feasible hardware unit capable of processing data and/or executing source separation algorithm <NUM> and software applications facilitating operation of ANC system <NUM> as described herein. In some embodiments, source separation processor <NUM> is coupled to a memory <NUM>, and source separation algorithm <NUM> and a sound signature database <NUM> reside in memory <NUM> during operation. Memory <NUM> generally includes storage chips, such as random access memory (RAM) chips, that store applications and data for processing by source separation processor <NUM>.

Source separation algorithm <NUM> may be similar to a conventional artificial intelligence or machine-learning algorithm trained to identify and separate one or more sound sources from an electronic reference signal <NUM>. Thus, source separation algorithm <NUM> may be configured to build a model from example inputs to make data-driven decisions, rather than following strictly static program instructions. In such embodiments, source separation algorithm <NUM> may be initially "trained" by simulating particular sound-generating conditions, and can then recognize sound signals that correspond to such sound-generating conditions during operation. According to the invention, source separation algorithm <NUM> is configured to compare electronic reference signal <NUM> to a sound signature database <NUM> to facilitate identification of one or more sound sources in electronic reference signal <NUM>, such as speech, air turbulence, road noise, and the like. In such embodiments, for a particular model of motor vehicle or aircraft, various sound sources can be recorded under a plurality of conditions, and characteristic reference signals generated by a reference microphone are included in sound signature database <NUM>. For example, road noise and air turbulence can be recorded at various velocities or simulated velocities, with and without cross-wind, different road surface conditions, etc. When source separation algorithm <NUM> recognizes one of these sound sources, a source-separated reference signal <NUM> can be generated to cancel or damp the particular sound source.

<FIG> is a flowchart of method steps for generating a source-separated reference signal, according to various embodiments.

As shown, a method <NUM> begins at step <NUM>, where source separation algorithm <NUM> receives electronic reference signal <NUM> from a reference microphone, for example reference microphone <NUM>. Generally, reference signal <NUM> is generated based on acoustic inputs from multiple sound sources. For example, as illustrated in <FIG> , reference microphone <NUM> receives acoustic input <NUM> and acoustic input <NUM>, and generates electronic reference signal <NUM> in response thereto.

In step <NUM>, source separation algorithm <NUM> selects one of the plurality of recorded sound signature stored in sound signature database <NUM>. Sound signature database may include a variety of sound signatures associated with a particular embodiment of ANC system <NUM>. Generally, sound signature database <NUM> include groups of representative sound signatures for each potential noise source that ANC system <NUM> is anticipated to damp. The sound signature database <NUM> may include a group of representative sound signatures of air turbulence generated when the specific model of motor vehicle travels at different velocities, another group of representative sound signatures associated with a specific window being opened as the specific model of motor vehicle travels at different velocities, another group of representative sound signatures associated with tire friction at various velocities and surface conditions, etc..

In step <NUM>, sound signature database <NUM> determines whether the recorded sound signature matches or substantially matches a portion of electronic reference signal <NUM>. In some embodiments, the portion may be a particular frequency band or bands. Alternatively or additionally, in some embodiments, the portion may be a signal or waveform super-positioned on other signals or waveforms in electronic reference signal <NUM>. If the recorded sound signature matched or substantially matches a portion of electronic reference signal <NUM>, method <NUM> proceeds to step <NUM>; if not, method <NUM> proceeds to step <NUM>.

In step <NUM>, source separation algorithm <NUM> selects the portion of electronic reference signal <NUM> that is matched by a recorded sound signature in step <NUM>. For example, the frequency band or particular waveform determined to match the recorded sound signature in step <NUM> may be temporarily stored for use as a component for generating a source-separated reference signal. Method <NUM> then proceeds to step <NUM>.

In step <NUM>, source separation algorithm <NUM> determines whether there are any sound signatures remaining in sound signature database <NUM> to be compared to electronic reference signal <NUM>. If yes, method <NUM> proceeds back to step <NUM>; if no, method <NUM> proceeds to step <NUM>.

In step <NUM>, source separation algorithm <NUM> generates a source-separated reference signal based on the one or more portions of electronic reference signal <NUM> selected in step <NUM>. Thus, the source-separated reference signal, i.e., source-separated reference signal <NUM> in <FIG> , represents acoustic inputs from sound sources recognized by source separation algorithm <NUM>. For a sound source recognized by source separation algorithm <NUM> to be a noise source, source-separated reference signal <NUM> may include a phase-shifted compensation signal configured to reduce the power of an acoustic input from the noise sound source in listening location <NUM>. For a sound source recognized by source separation algorithm <NUM> to be a sound source that is to be enhanced, source-separated reference signal <NUM> may include a phase-shifted compensation signal configured to increase the power of an acoustic input from the noise sound source in listening location <NUM>.

Controller <NUM> may be any suitable ANC controller configured to receive source-separated reference signal <NUM> from source separation processor <NUM> and an error signal <NUM> from error microphone <NUM>. In some embodiments, controller <NUM> shares computational resources with source separation processor <NUM>, such as memory <NUM>. In other embodiments, controller <NUM> is a separate computing device from source separation processor <NUM> and is operably coupled to a memory <NUM>. In addition to receiving source-separated reference signal <NUM>, controller <NUM> is configured to generate an electronic correction signal <NUM> based thereon to cause acoustic actuator <NUM> to generate acoustic correction signal <NUM>. Controller <NUM> includes an adaptive filter <NUM> that receives source-separated reference signal <NUM>, which represents the noise signal, and provides a compensation signal, i.e., electronic correction signal <NUM>, for reducing or eliminating the noise signal in listening location <NUM>. Controller <NUM> receives source-separated reference signal <NUM> from source separation processor <NUM>, and transmits electronic correction signal <NUM> to acoustic actuator <NUM>. Controller <NUM> includes adaptive filter <NUM> because the signal level and the spectral composition of noise to be suppressed, i.e., sound generated by sound source <NUM> or <NUM>, may vary over time. For example, when ANC system <NUM> is incorporated in a motor vehicle, adaptive filter <NUM> may adapt to changes of environmental conditions, such as variations in road surface, wind speed or direction, window position (i.e., open or closed), loading of the engine, etc..

Adaptation algorithm <NUM> is configured to estimate an unknown system by modifying the filter coefficients of adaptive filter <NUM> so that the transfer characteristic of adaptive filter <NUM> approximately matches the transfer characteristic of the unknown system. In ANC applications, adaptive filter <NUM> may include digital filters, for example finite impulse response (FIR) or infinite impulse response (11R) filters, whose filter coefficients are modified according to adaptation algorithm <NUM>. In addition, adaptation algorithm <NUM> adapts the filter coefficients in a recursive process that optimizes the filter characteristic of adaptive filter <NUM> by reducing or eliminating error signal <NUM> received from error microphone <NUM>.

Reference microphone <NUM> and error microphone <NUM> may be any technically feasible acoustic sensors suitable for use in ANC <NUM>. Reference microphone <NUM> generates an electronic reference signal <NUM> in response to sound inputs, such as an acoustic input <NUM> from sound source <NUM> and a sound input <NUM> from sound source <NUM>. Reference microphone <NUM> may be located proximate sound source <NUM> or sound source <NUM>, or at a point relatively close to each. For example, in an automobile, reference microphone <NUM> may be located within a door of the automobile, to facilitate generation of electronic reference signal <NUM> having high coherence with a particular sound source, such as air turbulence.

Error microphone <NUM> generates an electronic error signal <NUM> in response to an acoustic input <NUM> from sound source <NUM>, sound input <NUM> from sound source <NUM>, and acoustic correction signal <NUM> from acoustic actuator <NUM>. Error signal <NUM> is essentially the difference between the output of the particular sound source to be cancelled (either sound source <NUM> or <NUM>), and the output of adaptive filter <NUM>, i.e., electronic correction signal <NUM>, which is converted to acoustic correction signal <NUM> by acoustic actuator <NUM>. Error microphone <NUM> may be disposed near the area or location targeted for maximum noise reduction, such as listening location <NUM>. For example, in an automobile, error sensor <NUM> may be disposed within a head rest of a particular passenger or in the ceiling above a particular passenger. Alternatively, in a head phone system, an error microphone <NUM> may be disposed proximate the hearing cavity of each earcup.

Acoustic actuator <NUM> is an audio cancelling source of ANC system <NUM>, and may be any technically feasible speaker or other acoustic radiator suitable for use in ANC system <NUM>. In some embodiments, ANC <NUM> may include multiple acoustic actuators <NUM>, but for clarity only a single acoustic actuator is shown in <FIG>. Acoustic actuator <NUM> is generally located a minimum distance from sound sources <NUM> and <NUM>, so that the propagation time of sound signals from sound sources <NUM> and <NUM> to acoustic actuator <NUM> is greater than the processing time of source separation processor <NUM> and controller <NUM>.

Acoustic actuator <NUM> is configured to receive electronic correction signal <NUM> from controller <NUM>, and radiate acoustic correction signal <NUM> into listening location <NUM>. Acoustic actuator <NUM> may be located proximate error microphone <NUM> and/or the area or location targeted for maximum noise reduction. For example, in an automobile, acoustic actuator <NUM> may be located in a head rest of a particular seat. In such embodiments, a separate ANC system <NUM> may be employed for multiple different regions of the vehicle, such as the rear passenger area, the front passenger area, the driver area, etc..

Sound sources <NUM> and <NUM> may be any sound sources that generate acoustic signals within the effective operating area of ANC <NUM>. Thus, sound sources <NUM> and <NUM> may be unwanted noise, such as road noise or air turbulence, or sounds that are preferably not reduced in volume by ANC <NUM>, such as speech, music, audio content, and the like. For example, in some embodiments, sound source <NUM> may be a noise source while sound source <NUM> may be a sound source that is preferably not damped by ANC <NUM>. In such embodiments, reference microphone <NUM> receives acoustic input <NUM> from sound source <NUM> and sound input <NUM> from sound source <NUM>, and generates electronic reference signal <NUM>. When source separation algorithm <NUM> recognizes that acoustic input <NUM> from sound source <NUM> is a noise signal to be damped, source separation algorithm <NUM> generates source-separated reference signal <NUM> to cancel or damp sound source <NUM>. Therefore, source-separated reference signal <NUM> includes a phase-shifted compensation signal configured to reduce the power of acoustic input <NUM> from sound source <NUM> in listening location <NUM>. Additionally, in some embodiments, source separation algorithm <NUM> recognizes that sound input <NUM> from sound source <NUM> is an acoustic signal to be enhanced, such as audio content being played in listening location <NUM>, or speech. In such case, source-separated reference signal <NUM> includes a phase-shifted compensation signal configured to increase the power of acoustic input <NUM> from sound source <NUM> in listening location <NUM>.

According to some embodiments, an ANC system may be configured to determine directionality of one or more sound sources, and use such directionality to facilitate generation of a source-separated reference signal. One such example is illustrated in <FIG> , which is a block diagram of an ANC system <NUM>, according to various other embodiments. ANC system <NUM> may be substantially similar to ANC <NUM> in <FIG> , with the addition of multiple reference microphones <NUM> A and 231B, and a dynamic beam-forming module <NUM>. In the embodiment illustrated in <FIG> , ANC <NUM> includes two reference microphones 231A and 231B. In other embodiments, ANC <NUM> may include three or more reference microphones, each generating an electronic reference signal for use by dynamic beam-forming module <NUM>.

Reference microphones 231A and 231B are disposed separate from each other, so that acoustic input 151A (received from sound source <NUM> by reference microphone 231A) differs from acoustic input 151B (received from sound source <NUM> by reference microphone 231B). Similarly, acoustic input 161A (received from sound source <NUM> by reference microphone 231A) differs from acoustic input 161B (received from sound source <NUM> by reference microphone 231B). Consequently, electronic reference signal 271A, generated by reference microphone 231A, differs substantially from electronic reference signal <NUM> B, generated by reference microphone 231B. The difference between electronic reference signal 271A and electronic reference signal 271B facilitates the determination, by dynamic beam-forming module <NUM>, of the directionality of sound source <NUM> and sound source <NUM> with respect to listening location <NUM>.

Dynamic beam-forming module <NUM> may share computational resources with source-separating processor <NUM>, or may include a stand-alone computing system, such as a digital signal processor. Dynamic beam-forming module <NUM> is configured to employ adaptive beam-forming to partially or completely extract the acoustic inputs received from sound source <NUM> and sound source <NUM> from all acoustic inputs received by reference microphones <NUM> A and 231B. Generally, dynamic beam-forming module <NUM> has knowledge of the locations of sound source <NUM> and sound source <NUM>, so that time-of-arrival calculations can be used to determine which acoustic inputs received by reference microphones <NUM> A and 231B are generated by sound source <NUM> and which are generated by sound source <NUM>. Dynamic beam-forming module <NUM> can then generate a directional source-separated signal <NUM> that can be used to cancel or dampen a particular sound source located in a particular direction, such as sound source <NUM>. For example, in an embodiment in which sound source <NUM> is considered a noise source, directional source-separated signal <NUM> can include a phase-shifted compensation signal configured to reduce the power of acoustic input <NUM> from sound source <NUM> in listening location <NUM>. Dynamic beam-forming module <NUM> then transmits directional source-separated signal <NUM> to source separation processor <NUM> for further processing by source separation algorithm <NUM>, as described above in conjunction with <FIG>.

Thus, through the use of dynamic beam-forming module <NUM> and multiple reference microphones, a portion of an acoustic input received by reference microphones 231A and 231B can be associated with a particular sound source. In such embodiments, the particular sound source is determined based on the distance that the portion of the acoustic input has traveled and the direction from which the portion of the acoustic input has traveled. Consequently, a portion of an acoustic inputs received by reference microphones 231A and 231B can be damped or eliminated in listening location <NUM> when the portion of the acoustic input is associated with a noise source, e.g., sound source <NUM>.

<FIG> is a flowchart of method steps for actively cancelling noise, according to various embodiments.

As shown, a method <NUM> begins at step <NUM>, where the ANC system receives electronic reference signal <NUM> from a reference microphone, for example reference microphone <NUM>. Alternatively, in embodiments in which an ANC system includes dynamic beam-forming module <NUM>, the ANC system includes multiple reference microphones 231A and 231B, and receives multiple electronic reference signals 271A and 271B, as shown in <FIG>. It is noted that the reference signal or signals received in step <NUM> are generated based on acoustic inputs from multiple sound sources. For example, as illustrated in <FIG> , reference microphone <NUM> receives acoustic input <NUM> and acoustic input <NUM>, and generates electronic reference signal <NUM> in response thereto.

In optional step <NUM>, the ANC system generates directional source-separated reference signal <NUM>, and transmits the directional source-separated reference signal <NUM> to source separation processor <NUM>. In such embodiments, the ANC system includes dynamic beam-forming module <NUM>, which can associate a portion of the acoustic signals received by reference microphones <NUM> A and 231B with a particular sound source to be damped, for example sound source <NUM>. Dynamic beam-forming module <NUM> configures directional source-separated reference signal <NUM> to cancel or damp acoustic inputs determined to originate from a particular sound source located in a particular direction or location. For example, in one embodiment, sound source <NUM> may correspond to road noise from a lower region of a motor vehicle and the ANC system is configured to dampen such noise. Thus, in such an embodiment, acoustic inputs from the lower region of the motor vehicle may be assumed to be from sound source <NUM>, and source-separated reference signal <NUM> is configured to cancel or dampen acoustic inputs determined to originate from sound source <NUM>.

In step <NUM>, the ANC system determines a separated signal that corresponds to the acoustic input from one of the multiple sound sources used to generate electronic reference signal <NUM> received in step <NUM>. For example, in an embodiment in which sound source <NUM> is a noise source, source separation algorithm <NUM> identifies acoustic input <NUM> to be from sound source <NUM>, based on electronic reference signal <NUM> and on recorded sound signatures in sound signature database <NUM>. In embodiments in which optional step <NUM> is performed, source separation algorithm <NUM> identifies acoustic input <NUM> based on directional source-separated signal <NUM> rather than on electronic reference signal <NUM>.

In step <NUM>, source separation algorithm <NUM> of the ANC system generates source-separated reference signal <NUM> based on the separated signal determined in step <NUM>. Thus, source-separated reference signal <NUM> is configured to cancel or dampen the power of acoustic input <NUM> from sound source <NUM> in listening location <NUM>, but not the power of acoustic input <NUM> from sound source <NUM> in listening location <NUM>. Additionally, in embodiments in which a sound source, e.g., sound source <NUM>, is preferably enhanced, source-separated reference signal <NUM> may be configured to increase the power of acoustic input <NUM> in listening location <NUM>.

In step <NUM>, adaptation filter <NUM> of controller <NUM> receives source-separated reference signal <NUM> and generates electronic correction signal <NUM> based on source-separated reference signal <NUM>. Because source-separated reference signal <NUM> is based on a particular sound source identified by source separation algorithm <NUM>, there can be a high coherence between acoustic inputs from that particular sound source and source-separated reference signal <NUM>. Consequently, effective noise reduction of the sound source is possible.

In step <NUM>, acoustic actuator <NUM> receives electronic correction signal <NUM> generated by adaptation filter <NUM>, and radiates acoustic correction signal <NUM> into listening location <NUM>. Because source-separated reference signal <NUM> is configured only to cancel or dampen the power of acoustic input <NUM> from sound source <NUM> in listening location <NUM>, the power of acoustic input <NUM> in listening location <NUM> is largely unaffected by acoustic correction signal <NUM>. Therefore, the sound-cancelling acoustic correction signal <NUM> radiated into listening location <NUM> by acoustic actuator <NUM> only substantially cancels or damps acoustic inputs from sound source <NUM>. When sound source <NUM> is a sound source that is to be enhanced, radiation of acoustic correction signal <NUM> into listening location <NUM> can result in an increase in the power of acoustic input <NUM> in listening location <NUM>.

In step <NUM>, error microphone <NUM> receives acoustic input <NUM>, acoustic input <NUM>, and acoustic correction signal <NUM>, and generates error signal <NUM> in response thereto.

In step <NUM>, adaptive algorithm <NUM> in controller <NUM> receives error signal <NUM>, and, in response thereto, adapts the filter coefficients of adaptive filter <NUM> to minimize error signal <NUM>.

In sum, various embodiments set forth systems and techniques for active noise cancellation. A source separation algorithm enables the identification of acoustic inputs from a particular sound source based on a reference signal generated with one or more microphones. Consequently, the identified acoustic inputs can be cancelled or damped in a targeted listening location via an acoustic correction signal, where the acoustic correction signal is generated based on a sound source separated from the reference signal. Advantageously, the reference signal can be generated with a microphone, even though such a reference signal may include a combination of multiple acoustic inputs. Thus, noise sources that cannot be individually measured, for example with an accelerometer mounted on a vibrating structure, can still be identified and actively cancelled.

Aspects of the present embodiments may be embodied as a system, method or computer program product. Accordingly, aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit," "module" or "system. " Furthermore, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, enable the implementation of the functions/acts specified in the flowchart and/or block diagram block or blocks. Such processors may be, without limitation, general purpose processors, special-purpose processors, application-specific processors, or field-programmable processors or gate arrays.

Claim 1:
A method for actively cancelling noise, the method comprising:
receiving an electronic reference signal (<NUM>) from one or more microphones that receives a first acoustic input from a first sound source (<NUM>) and a second acoustic input from a second sound source (<NUM>), wherein the one or more microphones are coupled to a motor vehicle or aircraft;
selecting one of a plurality of recorded sound signatures stored in a database (<NUM>), wherein the plurality of recorded sound signatures comprises a group of representative sound signatures of noise sources that are anticipated to be cancelled or damped;
determining whether the selected recorded sound signature matches or substantially matches a portion of the electronic reference signal (<NUM>);
based on a match between the portion of the electronic reference signal (<NUM>) and the selected recorded sound signature, separating the portion of the electronic reference signal (<NUM>) from the electronic reference signal (<NUM>) as a separated signal;
determining whether there are any sound signatures remaining in the database (<NUM>) to be compared to the electronic reference signal (<NUM>) and, if there are sound signatures remaining in the database (<NUM>), selecting one of the remaining sound signatures;
generating a source-separated reference signal (<NUM>) based on the separated signals obtained by the match between the portion of the electronic reference signal (<NUM>) and each selected recorded sound signature such that the source-separated reference signal (<NUM>) represents the acoustic input of one of the first sound source (<NUM>) or the second sound source (<NUM>);
generating an electronic correction signal (<NUM>) based on the source-separated reference signal (<NUM>), wherein the electronic correction signal (<NUM>) comprises a phase-shifted compensation signal configured to reduce a power of a third acoustic input from the one of the first sound source (<NUM>) or the second sound source (<NUM>) in an area within the motor vehicle; and
converting the electronic correction signal (<NUM>) into an acoustic correction signal (<NUM>) in the area within the motor vehicle or aircraft by an acoustic actuator (<NUM>).