Patent Description:
This disclosure is generally directed to systems and methods for controlling a noise-cancellation output signal based on entertainment audio. Various examples are directed to systems and methods for controlling a noise-cancellation output signal based on entertainment audio.

<CIT>, <CIT>, <CIT> and <CIT> disclose prior art road noise cancellation systems.

The invention relates to a vehicle implemented noise-cancellation system and a system for monitoring entertainment audio according to the independent claims. Advantageous embodiments are set forth in the dependent claims.

In various implementations, a processor or controller can be associated with one or more storage media (generically referred to herein as "memory," e.g., volatile and non-volatile computer memory such as ROM, RAM, PROM, EPROM, and EEPROM, floppy disks, compact disks, optical disks, magnetic tape, Flash, OTP-ROM, SSD, HDD, etc.). In some implementations, the storage media can be encoded with one or more programs that, when executed on one or more processors and/or controllers, perform at least some of the functions discussed herein. Various storage media can be fixed within a processor or controller or can be transportable, such that the one or more programs stored thereon can be loaded into a processor or controller so as to implement various aspects as discussed herein. The terms "program" or "computer program" are used herein in a generic sense to refer to any type of computer code (e.g., software or microcode) that can be employed to program one or more processors or controllers.

Other features and advantages will be apparent from the description and the claims.

An adaptive noise-cancellation system employs the use of at least one reference signal from a reference sensor in order to generate a noise-cancellation signal. If the noise-cancellation system is deployed in a vehicle, the reference sensors are typically accelerometers operably mounted to the vehicle to detect vibrations in the chassis, which are transduced by the chassis into what is perceived by a passenger as road noise. If the entertainment audio system of the vehicle is playing loud music (specifically loud music with deep bass hits or thumps), the music may cause vibrations in the car that excite the accelerometers. This may give the noise-cancellation system a false indication of road noise, and thus cause it to play this excitation through secondary noise-cancellation speakers. Playing this excitation through the secondary noise-cancellation speakers can corrupt the accelerometers and/or muddle the entertainment audio within the cabin of the vehicle. Further, at particular loud volumes, the music may completely overwhelm any road noise, thus eliminating the need for road noise-cancellation.

The provided system for monitoring entertainment audio addresses the aforementioned problems. The system utilizes two sets of thresholds. The first set of thresholds triggers the system to enable or disable the adaptation of an adaptive filter of the noise-cancellation system. The second set of thresholds triggers the system to enable, attenuate, or disable the noise-cancellation signal. Accordingly, as the entertainment audio increases in volume and magnitude, the system first disables the adaptation of the adaptive filter, then attenuates the noise-cancellation signal, then completely disables the noise-cancellation signal. Conversely, as the entertainment audio decreases, the system first enables the noise-cancellation signal, then reduces the attenuation (thereby increasing the amplitude) of the noise-cancellation signal, and then enables the adaptation of the adaptive filter.

The system monitors the entertainment based on the signals generated by the entertainment audio system. For example, the system can monitor the left and right audio channel signals generated by the entertainment audio system. In an alternative example, the system monitors the numerous output audio channel signals provided to the vehicle loudspeakers. The system can perform a weighted or un-weighted root-mean-squared (RMS) calculation of the monitored signals to determine an entertainment audio monitor signal. The system then controls the adaptation of the adaptive filter and the noise-cancellation signal based on the relationship of the entertainment audio monitor signal and the aforementioned thresholds.

According to the invention, such a vehicle-implemented noise-cancellation system will be briefly described, for purposes of illustration, in connection with <FIG> and <FIG>. <FIG> is a schematic view of an example noise-cancellation system <NUM>. Noise-cancellation system <NUM> is configured to destructively interfere with undesired sound in at least one cancellation zone <NUM> within a predefined volume <NUM> such as a vehicle cabin. At a high level, an example of noise-cancellation system <NUM> can include a reference sensor <NUM>, an error sensor <NUM>, an actuator <NUM>, and a controller <NUM>.

In an example, reference sensor <NUM> is configured to generate noise signal(s) <NUM> representative of the undesired sound, or a source of the undesired sound, within predefined volume <NUM>. For example, as shown in <FIG>, reference sensor <NUM> can be an accelerometer, or a plurality of accelerometers, mounted to and configured to detect vibrations transmitted through a vehicle structure <NUM>. Vibrations transmitted through the vehicle structure <NUM> are transduced by the structure into undesired sound in the vehicle cabin (perceived as road noise), thus an accelerometer mounted to the structure provides a signal representative of the undesired sound.

Actuators <NUM> are speakers distributed in discrete locations about the perimeter of the predefined volume. In an example, four or more speakers can be disposed within a vehicle cabin, each of the four speakers being located within a respective door of the vehicle and configured to project sound into the vehicle cabin. In alternate examples, speakers can be located within a headrest, or elsewhere in the vehicle cabin.

A noise-cancellation signal <NUM> can be generated by controller <NUM> and provided to one or more speakers in the predefined volume, which transduce the noise-cancellation signal <NUM> to acoustic energy (i.e., sound waves). The acoustic energy produced as a result of noise-cancellation signal <NUM> is approximately <NUM>° out of phase with-and thus destructively interferes with-the undesired sound within the cancellation zone <NUM>. The combination of sound waves generated from the noise-cancellation signal <NUM> and the undesired noise in the predefined volume results in cancellation of the undesired noise, as perceived by a listener in a cancellation zone.

Because noise-cancellation cannot be equal throughout the entire predefined volume, noise-cancellation system <NUM> is configured to create the greatest noise-cancellation within one or more predefined cancellation zones <NUM> within the predefined volume. The noise-cancellation within the cancellation zones can reduce undesired sound by approximately <NUM> dB or more (although in varying examples, different amounts of noise-cancellation can occur). Furthermore, the noise-cancellation can cancel sounds in a range of frequencies, such as frequencies less than approximately <NUM> (although other ranges are possible).

Error sensor <NUM>, disposed within the predefined volume, generates an error sensor signal <NUM> based on detection of residual noise resulting from the combination of the sound waves generated from the noise-cancellation signal <NUM> and the undesired sound in the cancellation zone. The error sensor signal <NUM> is provided to controller <NUM> as feedback, error sensor signal <NUM> representing residual noise uncanceled by the noise-cancellation signal. Error sensors <NUM> can be, for example, at least one microphone mounted within a vehicle cabin (e.g., in the roof, headrests, pillars, or elsewhere within the cabin).

It should be noted that the cancellation zone(s) can be positioned remotely from error sensor <NUM>. In this case, the error sensor signal <NUM> can be filtered to represent an estimate of the residual noise in the cancellation zone(s). In either case, the error signal will be understood to represent residual undesired noise in the cancellation zone.

In an example, controller <NUM> can comprise a nontransitory storage medium <NUM> and processor <NUM>. In an example, non-transitory storage medium <NUM> can store program code that, when executed by processor <NUM>, implements the various filters and algorithms described below. Controller <NUM> can be implemented in hardware and/or software. For example, the controller can be implemented by a SHARC floating-point DSP processor, but it should be understood that controller <NUM> can be implemented by any other processor, FPGA, ASIC, or other suitable hardware.

<FIG> shows a block diagram of an example of noise-cancellation system <NUM>, including a plurality of filters implemented by controller <NUM>. As shown, the controller can define a control system including Wadapt filter <NUM> and an adaptive processing module <NUM>.

Wadapt filter <NUM> is configured to receive the noise signal <NUM> of reference sensor <NUM> and to generate noise-cancellation signal <NUM>. Noise-cancellation signal <NUM>, as described above, is input to actuator <NUM> where it is transduced into the noise-cancellation audio signal that destructively interferes with the undesired sound in the predefined cancellation zone <NUM>. Wadapt filter <NUM> can be implemented as any suitable linear filter, such as a multi-input multi-output (MIMO) finite impulse response (FIR) filter. Wadapt filter <NUM> employs a set of coefficients which define the noise-cancellation signal <NUM> and which can be adjusted to adapt to changing behavior of the vehicle response to road input (or to other inputs in non-vehicular noise-cancellation contexts).

The adjustments to the coefficients can be performed by an adaptive processing module <NUM>, which receives as inputs the error sensor signal <NUM> and the noise signal <NUM> and, using those inputs, generates a filter update signal <NUM>. The filter update signal <NUM> is an update to the filter coefficients implemented in Wadapt filter <NUM>. The noise-cancellation signal <NUM> produced by the updated Wadapt filter <NUM> will minimize error sensor signal <NUM>, and, consequently, the undesired noise in the cancellation zone.

The coefficients of Wadapt filter <NUM> at time step n can be updated according to the following equation: <MAT>
where T̃de is an estimate of the physical transfer function between actuator <NUM> and the noise-cancellation zone <NUM>, T̃'de is the conjugate transpose of T̃de, e is the error signal, and x is the output signal of reference sensor <NUM>. In the update equation, the output signal x of reference sensor is divided by the norm of x, represented as ||xl|<NUM>.

In application, the total number of filters is generally equal to the number of reference sensors (M) multiplied by the number of speakers (N). Each reference sensor signal is filtered N times, and each speaker signal is then obtained as a summation of M signals (each sensor signal filtered by the corresponding filter).

Noise-cancellation system <NUM> further includes an adjustment module <NUM> configured to vary at least one of a power of the noise-cancellation signal <NUM> and rate of adaptation of the adaptive filter Wadapt filter <NUM> as implemented by the adaptive processing module <NUM>. The adjustment module <NUM> varies the noise-cancellation signal <NUM> and/or the rate of adaptation of the adaptive filter <NUM> according to the voltage of one or more entertainment audio signals <NUM> generated by the entertainment audio system <NUM>. These entertainment audio signals <NUM> are, either directly or following further processing, transduced by one or more loudspeakers to produce entertainment audio, such as music. For example, the vehicle can include several loudspeakers placed around the vehicle to form a surround sound subsystem. In some examples, as many as <NUM> or <NUM> loudspeakers are used in a vehicle. As noted previously, loud music with deep bass sounds can vibrate the reference sensor <NUM> (such as an accelerometer) to generate a noise signal <NUM> falsely indicative of road noise. The noise-cancellation signal <NUM> created to cancel this non-existent road noise can muddle the entertainment audio played in the cabin.

An entertainment audio estimator <NUM> generates a single entertainment audio monitor signal <NUM> based on the one or more entertainment audio signals <NUM>. The entertainment audio monitor signal <NUM> can be an RMS estimate of the one or more entertainment audio signals <NUM>. For example, the one or more entertainment audio signals <NUM> can include a left channel audio signal 140a and a right channel audio signal 140b, such as the left and right channel of a stereo audio track on a compact disc, digital music file, or digital music stream played by the entertainment audio system <NUM>. The entertainment audio monitor signal <NUM> can then be an RMS estimate of the left channel audio signal 140a and the right channel audio signal 140b. While this example describes the entertainment audio monitor signal <NUM> as the result of an RMS estimate of one or more audio signals, in further examples the entertainment audio monitor signal <NUM> could be any other metric or figure corresponding to the loudness of entertainment audio within the vehicle.

According to a further example, the one or more entertainment audio signals <NUM> can include a plurality of output audio channel signals. The entertainment audio system <NUM> can generate an output audio channel signal for each loudspeaker positioned in the vehicle based on the left channel audio signal 140a and/or the right channel audio signal 140b. The output audio channel signals can vary based on a wide range of factors, such as loudspeaker type (woofer, tweeter, mid-range driver, etc.), loudspeaker frequency range, loudspeaker vehicle placement, vehicle audio tuning, etc. The entertainment audio monitor signal <NUM> can be a weighted RMS estimate of the plurality of output audio channel signals.

Ideally, the entertainment audio signals <NUM> used to generate the entertainment audio monitor signal <NUM> reflect the entertainment audio played by the loudspeakers as closely as possible. In one example, entertainment audio signals <NUM> have been processed by one or more equalizers. The equalizers can be used to tune the entertainment audio to spatial and/or acoustic features of the vehicle, or simply to account for user preferences. In a further example, the entertainment audio monitor signal <NUM> may be generated based on a specific frequency range of the entertainment audio signals <NUM>.

The entertainment audio monitor signal <NUM> generated by the entertainment audio estimator <NUM> is provided to an entertainment audio monitor <NUM>. The entertainment audio monitor <NUM> controls the adjustment module <NUM> to prevent muddling of the entertainment audio played in the vehicle. The entertainment audio monitor <NUM> tracks the magnitude of the entertainment audio monitor signal <NUM> and compares the magnitude to two sets of thresholds. A first set of thresholds <NUM>, <NUM> enables or disables the adaptation of the adaptive filter <NUM>. A second set of thresholds <NUM>, <NUM> controls the strength of the noise-cancellation signal <NUM>.

The first two thresholds (adaptation freeze threshold <NUM> and adaptation enable threshold <NUM>) work on practically turning on and off the adaptation of the adaptive filter <NUM> (and therefore the noise-cancellation system as a whole) by following hysteresis. If the entertainment audio monitor signal <NUM> exceeds the adaptation freeze threshold <NUM>, the entertainment audio in the vehicle may be loud enough to corrupt the reference sensors <NUM> (e.g., accelerometers). If the noise-cancellation system <NUM> is allowed to adapt, the system <NUM> may adapt to the entertainment audio (rather than any road noise) and essentially muddle the desired entertainment audio. Therefore, when the entertainment audio monitor signal <NUM> exceeds this adaptation freeze threshold <NUM>, the system <NUM> (via adjustment module <NUM>) can stop the road noise-cancellation adaptation by setting the adaptation step size to <NUM>. The adaptive filter <NUM> can adapt again only when the entertainment audio monitor signal <NUM> subsequently dips below the adaptation enable threshold <NUM>.

The second set of two thresholds (cancellation enable threshold <NUM> and cancellation disable threshold <NUM>) serve a different purpose. A driver's choice of the loudness of entertainment audio is subjective, and at a certain point (corresponding to the cancellation enable threshold) entertainment audio may be so loud that it starts to mask all road noise. When road noise is not the dominating audible component in the vehicle cabin, road noise-cancellation is no longer necessary. So, to forego the road noise-cancellation whenever the entertainment audio reaches this loud volume, when the entertainment audio monitor signal <NUM> exceeds a cancellation enable threshold <NUM>, road noise-cancellation is disabled by ramping down the speaker gain associated with actuator <NUM> from <NUM> to <NUM>. Alternatively, the noise-cancellation signal <NUM> may be ramped down by an attenuator prior to reception by actuator <NUM>. When the entertainment audio monitor signal <NUM> exceeds the cancellation disable threshold <NUM>, the road noise-cancellation system <NUM> is entirely disabled by setting the speaker gain to <NUM>.

<FIG> shows how the entertainment audio monitor signal <NUM> may be used to control the adaptation of the adaptive filter <NUM> and the magnitude of the road noise-cancellation signal <NUM> according to the four thresholds <NUM>, <NUM>, <NUM>, <NUM> defined above. As shown in <FIG>, the entertainment audio monitor signal <NUM> increases after the one second mark such that it crosses the adaptation freeze threshold <NUM> just after the three second mark. At this point, the adaptation of the adaptive filter <NUM> is disabled, and remains disabled until the entertainment audio monitor signal <NUM> dips below the adaptation enable threshold <NUM> just after the four second mark. Adaptation remains enabled until the entertainment audio monitor signal <NUM> again exceeds adaptation freeze threshold <NUM> in between the five and six second mark. The entertainment audio monitor signal <NUM> then exceeds the cancellation enable threshold <NUM> from just after the six second mark to just after the seven second mark, and again at around the <NUM> second mark to the eight second mark. During these periods, the noise-cancellation audio signal <NUM> is attenuated relative to the amplitude of the entertainment audio monitor signal <NUM>. The entertainment audio monitor signal <NUM> then exceeds the cancellation disable threshold <NUM> from just after the eight second mark to approximately the <NUM> second mark. During this period, the road noise-cancellation audio signal <NUM> is disabled entirely, and the system <NUM> does not cancel any road noise. Road noise-cancellation is re-enabled after the <NUM> second mark, and is amplified between the <NUM> second mark and the <NUM> second mark. Lastly, as the entertainment audio monitor signal <NUM> continues to decrease after the <NUM> second mark, the noise-cancellation signal <NUM> is no longer attenuated. Filter <NUM> adaptation is re-enabled when the entertainment audio monitor signal <NUM> dips below the adaptation enable threshold <NUM> at approximately <NUM> seconds.

In a further example, the entertainment audio monitor <NUM> may employ additional thresholds to disable/enable additional vehicle subsystems. For example, audio generated by an electric vehicle pedestrian warning system, such as an Acoustic Vehicle Alerting System (AVAS), may be enabled, disabled, amplified, and/or attenuated according to the entertainment audio monitor signal <NUM>.

The noise-cancellation systems <NUM> described above are merely provided as examples of such a system <NUM>. This system <NUM>, variants of this system <NUM>, and other suitable noise-cancellation systems can be used within the scope of this disclosure.

For the purposes of this disclosure, any instance of an equation being used to determine a value (e.g., the equations used to determine the intermediate values) can be implemented as a look-up table, the values of which are dictated by the equation, or can be calculated in real time.

The functionality described herein, or portions thereof, and its various modifications (hereinafter "the functions") can be implemented, at least in part, via a computer program product, e.g., a computer program tangibly embodied in an information carrier, such as one or more non-transitory machine-readable media or storage device, for execution by, or to control the operation of, one or more data processing apparatus, e.g., a programmable processor, a computer, multiple computers, and/or programmable logic components.

Actions associated with implementing all or part of the functions can be performed by one or more programmable processors executing one or more computer programs to perform the functions of the calibration process. All or part of the functions can be implemented as, special purpose logic circuitry, e.g., an FPGA and/or an ASIC (application-specific integrated circuit).

Components of a computer include a processor for executing instructions and one or more memory devices for storing instructions and data.

Claim 1:
A vehicle implemented noise-cancellation system (<NUM>), comprising:
a noise-cancellation subsystem disposed in a vehicle, the noise-cancellation system comprising an adaptive filter (<NUM>) being adjusted according to a reference signal (<NUM>) and an error signal (<NUM>), the adaptive filter outputting a noise-cancellation signal (<NUM>), which, when transduced into a noise-cancellation audio signal by a speaker (<NUM>), cancels road noise within at least one zone (<NUM>) within a cabin of the vehicle; and
an entertainment audio monitoring subsystem, configured to:
generate an entertainment audio monitor signal (<NUM>) corresponding to entertainment audio originating from an entertainment audio system (<NUM>) of the vehicle;
characterized in that the entertainment audio monitoring subsystem is further configured to:
disable adaptation of the adaptive filter when the amplitude of the entertainment audio monitor signal is greater than an adaptation freeze threshold (<NUM>);
subsequent to disabling adaptation of the adaptive filter, enable adaptation of the adaptive filter when the amplitude of the entertainment audio monitor signal is less than an adaptation enable threshold (<NUM>)
disable the noise-cancellation audio signal when the amplitude of the entertainment audio monitor signal is greater than a cancellation disable threshold (<NUM>); and
attenuate the noise-cancellation audio signal when the amplitude of the entertainment audio monitor signal is greater than a cancellation enable threshold (<NUM>), wherein the attenuation of the noise-cancellation audio signal increases relative to the amplitude of the entertainment audio monitor signal when the amplitude of the entertainment audio monitor signal is less than the cancellation disable threshold.