Patent Description:
Disclosed herein are methods and systems relating to proximity compensation for remote microphone techniques.

Document <CIT> discloses a noise treatment device comprising at least one local noise sound sensor and at least one sound system having a support and at least one sound actuator. The device also includes a position sensor for determining the position of a person's head, at least one treatment unit connected to the local noise sound sensor to receive a local noise signal and configured to deliver a control signal to each sound actuator, the control signal being a function of the local noise signal and of at least one transfer function per ear, and active matching means co-operating with the position sensor in order to keep each transfer function used in preparing each control signal representative of the path to be traveled by the anti-noise.

Document <CIT> discloses a method for attenuating road noise in a vehicle cabin. The method includes filtering a noise signal representative of road noise with a first fixed filter to provide an attenuation signal, and filtering the attenuation signal with an adaptive filter to provide a first filtered attenuation signal. The first filtered attenuation signal is provided to an electro-acoustic transducer for transduction to acoustic energy, thereby to attenuate the road noise in a vehicle cabin at an expected position of an occupant's ears. The method also includes receiving a microphone signal representative of the acoustic energy, filtering the attenuation signal with a second fixed filter to provide a second filtered attenuation signal, and updating a set of variable filter coefficients of the adaptive filter based on the microphone signal and the second filtered attenuation signal to accommodate for variations in a transfer function of the speaker.

Document <CIT> discloses a method of active noise control comprising: Detecting a first occupant position of a first occupant and detecting a second occupant position of a second occupant within a defined space; Receiving an error signal from a microphone located at a microphone location within the defined space; Generating an anti-noise signal based at least in part on the error signal and the detected occupant positions; and Transmitting the anti-noise signal to a speaker; and further comprising generating a modified error signal by modifying the error signal based on the first occupant position relative to the microphone location and on the second occupant position relative to the microphone location, wherein generating an anti-noise signal is based at least in part on the modified error signal.

Vehicles often include active noise cancelation (ANC) technologies to reduce ambient noise within the vehicle cabin. Such ANC technologies may require various microphones to be placed within the vehicle cabin. These microphones may aid the ANC system in generating an error signal. However, often times it is not practical to have a physical microphone present at certain locations within the vehicle cabin. In these cases, remote microphone technology may be used.

A remote microphone system for a vehicle includes at least one physical microphone arranged within a vehicle cabin configured to generate an error signal at a virtual microphone location within the vehicle, a database configured to maintain a look up table of premeasured seat positions and associated transfer functions, and a processor. The processor is configured to receive a seat position indicative of a seat location within the vehicle, determine whether one of the premeasured positions corresponds to the seat position, in response to one of the premeasured positions not corresponding to the seat position, interpolate the transfer functions from at least two known premeasured positions, and apply the transfer function interpolated from the at least two known premeasured positions to a primary noise signal of the at least one physical microphone to generate the error signal.

A remote microphone system for estimating an error signal for noise cancelation within a vehicle includes at least one physical microphone arranged within a vehicle cabin configured to generate an error signal at a virtual microphone location within the vehicle at a vehicle seat, a database configured to maintain a look up table of premeasured seat positions and associated transfer functions, and a processor. The processor may be configured to receive a seat position of the vehicle seat, determine whether one of the premeasured positions corresponds to the seat position, in response to one of the premeasured positions not corresponding to the seat position, interpolate the transfer functions from at least two known premeasured positions, and apply the transfer function interpolated from the at least two known seat positions to a primary noise signal of the at least one physical microphone to generate the error signal.

The embodiments of the present disclosure are pointed out with particularity in the appended claims. However, other features of the various embodiments will become more apparent and will be best understood by referring to the following detailed description in conjunction with the accompanying drawings in which:.

As required, detailed embodiments of the present embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the embodiments that may be embodied in various and alternative forms.

Traditionally, remote microphone techniques take the physical microphones within the vehicle and applicate an error signal at a location where there is no physical microphone. This remote or virtual location is often in an area targeted to be the occupant's ear. This remote microphone technique involves a preliminary stage where measurements are made with microphones at the physical and virtual locations whereby the relationship between these two locations is identified. A transfer function between these two locations is created, either from a primary noise measurement or via an acoustic transfer function method using an omnidirectional source. This transfer function can exist either from a single physical microphone to a single virtual microphone, or with multiple physical microphones to a single virtual microphone. The latter example may be used as often a single physical microphone cannot always approximate the signal at the virtual location.

However, existing remote microphone technologies assume a fixed location between the physical and virtual microphone. This may not be the case when an occupant moves or adjusts his or her seat. Upon such movement of the seat, so does the occupant's ear location, and thus rendering the virtual location of the virtual microphone inaccurate. This may affect the cancellation performance and stability of the ANC system.

Described herein is system that determines a transfer function of a virtual microphone based on an occupant's seat position. Certain seat positions may be premeasured and associated with transfer functions. Thus, the transfer function may be determined and selected based on a current seat position. This may be done by comparing the seat location to a set of premeasured positions. If the seat location corresponds to one of the premeasured positions, then the transfer function associated with the premeasured position is selected. If the seat location does not correspond to one of the premeasured positions, then the transfer function will be interpolated between the premeasured positions. That is, if the seat position is between a first premeasured position and a second premeasured position, then the transfer function will be selected based on an interpolation of the transfer functions associated with each of the first and second premeasured positions.

<FIG> illustrates an example proximity compensation system <NUM> for remote microphone technology (RMT). The system <NUM> may be included in a vehicle <NUM> and include a processor <NUM> configured to carry out the methods and processes described herein. The processor <NUM> may include a controller (shown as controller <NUM> in <FIG>) and memory <NUM>, as well as other components specific for audio processing within the vehicle <NUM>. The processor <NUM> may be one or more computing devices such as a quad core processor for processing commands, such as a computer processor, microprocessor, or any other device, series of devices or other mechanisms capable of performing the operations discussed herein. The memory may store instructions and commands. The instructions may be in the form of software, firmware, computer code, or some combination thereof. The memory may be in any form of one or more data storage devices, such as volatile memory, nonvolatile memory, electronic memory, magnetic memory, optical memory, or any other form of data storage device. In one example, the memory may include 2GB DDR3, as well as other removable memory components such as a <NUM> GB micro SD card.

The memory <NUM> stores a look up table of transfer functions to be applied and associated with various seat locations and positions. These premeasured transfer functions are associated with a premeasured position. If the seat position corresponds to one of the premeasured positions, then the transfer function Ĥ(z) associated with the premeasured position is selected. If the seat position does not correspond to one of the premeasured positions, then a transfer function Ĥ(z) is interpolated between the premeasured positions. That is, if the seat position is between a first premeasured position and a second premeasured position, then the transfer function Ĥ(z) will be selected based on an interpolation of the transfer functions Ĥ(z) associated with each of the first and second premeasured positions.

The processor <NUM> is in communication with at least one physical microphone <NUM>. In the example in <FIG>, the physical microphone <NUM> may include a plurality of physical microphones <NUM>. The system <NUM> may include speakers <NUM>. The speakers <NUM> may be arranged throughout the vehicle to provide audio to the vehicle cabin. The speakers <NUM> may include various drivers includes mid-range drivers, tweeters and woofers. These speakers <NUM> may be arranged throughout the vehicle. The system <NUM> may also include an amplifier <NUM>.

The vehicle <NUM> includes various vehicle seats <NUM>. These seats <NUM> may be areas where passengers and occupants typically sit during use of the vehicle. As explained above, RMT technology may include virtual microphone locations. <FIG> illustrates at least one virtual microphone location. As explained, the virtual microphone location may be a location near an occupant's ear. Each seat <NUM> may have at least one virtual microphone <NUM> at a virtual microphone location associated with it. In the example in <FIG>, each seat <NUM> has two virtual microphones <NUM> associated therewith, one on either side of the seat <NUM>.

Each seat <NUM> may include at least one sensor <NUM> configured to detect the seat position. The seat location may be the relative position of the seat <NUM> within the vehicle <NUM>. Vehicle seats <NUM> may be adjusted vertically, laterally, axially, horizontally, etc. The seat location may include one or more of a vertical, lateral, axial, positions. The one or more sensors <NUM> may provide the processor <NUM> with the seat location. The look up table within the memory <NUM> may then in turn be used to associate a transfer function Ĥ(z) with a premeasured seat position.

<FIG> illustrates an example remote microphone technology diagram for the system <NUM> of <FIG>. The system <NUM>, as explained, may include a processor <NUM>, also described herein as a controller <NUM>. The various signals and paths provided in <FIG> include:.

The controller <NUM> may output a control signal y(n) to a secondary path Sp(z). The secondary path Sp(z) may produce an anti-noise signal yp(n) to the physical microphone <NUM>. The controller <NUM> may provide the control signal y(n) to an estimated secondary (electroacoustic) path Ŝp(z) to the virtual microphone <NUM>. The estimated secondary path may provide an estimated anti-noise signal ŷp(n) at the virtual microphone <NUM>.

The physical microphone <NUM> may receive a primary noise source signal dm(n) and the secondary anti-noise signal ym(n) and output an error signal em(n) assessed at the physical microphone location. The estimated anti-noise signal ŷe(n) may be removed or subtracted from the error signal em(n) at <NUM> to provide an estimated primary noise signal d̂e(n) at the physical location at <NUM>.

An estimated transfer function Ĥ(z) may be applied to the estimated primary noise signal d̂e(n) at the physical location <NUM> and produce an estimated primary noise signal d̂v(n) at the virtual microphone <NUM>. This transfer function Ĥ(z) may be generated and determined based on a preliminary identification stage or interpolation between the stored transfer functions Ĥ(z) between the physical and virtual microphones so that cancellation performance is maintained and stability is not an issue if the occupant moves their seat <NUM>. This is described in more detail below. Because the transfer function is based on the seat location, the transfer function is especially relevant to the location of the virtual microphone <NUM>.

The controller <NUM> also provides the control signal y(n) to an estimated secondary (electroacoustic) path to the virtual microphone <NUM>. The estimated secondary path to the virtual microphone <NUM> may provide an estimated anti-noise signal at the virtual location to the virtual microphone <NUM>. The virtual microphone <NUM> may receive the estimated primary noise signal at the virtual location, add it to the estimated anti-noise signal at the virtual location, and provide an estimated error at the virtual microphone location.

<FIG> illustrates an example schematic for approximating the transfer function using adaptive filters and a least mean square (LMS) optimization routine to calculate the coefficients of the finite impulse response (FIR) filters that represent the transfer function. This method may also be related to either the primary noise signals or the secondary path. In this example transfer function, the filter coefficients may change as the seat locations change.

Additionally or alternatively, the transfer function may be approximated as a ratio of cross spectral density (physical to virtual signals) and the auto spectral density (physical signal) of the primary noise signals, represented by: <MAT>.

The above example transfer function may be dependent on the linearity of the primary noise signals and is application dependent.

Referring to <FIG>, the use of LMS to approximate the transfer function allows the system <NUM> to store multiple filter coefficients based on the seat location. This may include multiple measurements in the preliminary identification stage. The controller <NUM> may recognize a seat location as being one of a plurality of premeasured positions. The controller <NUM> may retrieve the transfer function Ĥ(z) based on the recognized seat location. Alternatively, a series of discrete transfer functions Ĥ(z) could be measured and then interpolated between as the seat <NUM> is moved along the premeasured positions.

Thus, the transfer function Ĥ(z) may be determined and selected based on the seat position. This may be done by comparing the seat location to the premeasured positions. If the seat location corresponds to the premeasured positions, then the transfer function Ĥ(z) associated with the premeasured position is selected. If the seat location does not correspond to one of the premeasured positions, then the transfer function Ĥ(z) will be interpolated between the premeasured positions. That is, if the seat position is between a first premeasured position and a second premeasured position, then the transfer function Ĥ(z) will be selected based on an interpolation of the transfer functions Ĥ(z) associated with each of the first and second premeasured positions.

Current head tracking methods are more cumbersome and many vehicles are not equipped with such capabilities. This mechanism avoids the needs for a specific head tracking device, camera, ultrasonic sensors, etc., and uses existing elements.

<FIG> illustrates an example schematic illustrating the use of the transfer function Ĥ(z) between the physical and virtual microphones that changes with the seat position. In the example of <FIG>, two physical microphones <NUM> and one virtual microphone <NUM> (not shown in <FIG>), may be used. In <FIG>, M<NUM> and M<NUM> are transfer functions between the physical and virtual microphone <NUM> that changes with seat position.

<FIG> illustrates another example schematic illustrating the use of the transfer function Ĥ(z) between the physical and virtual microphones that changes with the seat position. Multiple physical microphones may be used for virtual microphone prediction. The estimated secondary path Sl,m(n) may provide an estimated anti-noise signal ym(n) at the virtual microphone <NUM>. The physical microphone <NUM> may receive a primary noise source signal de'm(n) and the secondary anti-noise signal yv'm(n) and output an error signal ev'm(n) assessed at the physical microphone location. A Fast Fourier Transform may be applied to the error signal ev'm(n). Other summed cross spectrum, Fast Fourier Transform, Inverse Fast Fourier Transform, matrices, etc may also be used in the proximity compensation.

An estimated transfer function Ĥ(z) may be applied to the estimated primary noise signal d̂e(n) at the physical location <NUM> and produce an estimated primary noise signal d̂v(n) at the virtual microphone <NUM>. <FIG> illustrates an example process <NUM> for determining the transfer function Ĥ(z). This process <NUM> may be carried out by the controller/processor <NUM>. The process <NUM> may begin at block <NUM> where the controller <NUM> may receive the current seat position from one of the seats <NUM>.

At block <NUM>, the controller <NUM> may determine whether the current seat position corresponds to a premeasured seat position. If so, the process <NUM> proceeds to block <NUM>. If not, the process <NUM> proceeds to block <NUM>.

At block <NUM>, the controller <NUM> selects the transfer function Ĥ(z) associated with the corresponding premeasured seat position.

At block <NUM>, the controller <NUM> selects the transfer function Ĥ(z) based on an interpolation of at least two known premeasured positions. That is, the transfer function may be determined by selecting a transfer function between the transfer functions corresponding to two known premeasured functions.

Claim 1:
A remote microphone system (<NUM>) for a vehicle (<NUM>) comprising:
at least one physical microphone (<NUM>) arranged within a vehicle cabin configured to generate an error signal (em(n)) at a virtual microphone location within the vehicle (<NUM>);
a database configured to maintain a look up table of premeasured seat positions and associated transfer functions (Ĥ(z));
characterised by a processor (<NUM>) configured to receive a seat position indicative of a seat location within the vehicle (<NUM>);
determine whether one of the premeasured positions corresponds to the seat position;
in response to one of the premeasured positions not corresponding to the seat position, interpolate the transfer functions (Ĥ(z)) from at least two known premeasured positions; and
apply the transfer function (Ĥ(z)) interpolated from the at least two known premeasured positions to a primary noise signal (d̂e(n)) of the at least one physical microphone (<NUM>) to generate the error signal (em(n)).