Variable gain active noise canceling system with improved residual noise sensing

An earpiece adapted to be held proximate a user's ear, the earpiece comprising:

• a sound generator, responsive to drive signals applied thereto, for generating anti-noise;
• a sensor for generating a residual signal indicative of the sum of ambient sounds and anti-noise at the location of the sensor;
• and
• an exterior shell comprising an forward lip for disposition proximate the users ear, a rear portion, and a transverse portion intermediate said lip and rear portions forming an interior cavity;
• and at least one aperture in a transverse portion, inset from said forward lip, of said exterior shell communicating with said interior cavity disposed rearwardly of said sound generator to enhance low frequency response of the earpiece and,
• wherein the transverse portion is a side wall joining the forward lip to the rear portion that is substantially perpendicular to the rear wall in the region of the at least one aperture and wherein the location of said at least one aperture in the traverse wall provides protection from blockage of said at least one aperture.

An active noise cancelling system, comprising:

• a sound generator for generating an anti-noise field in response to drive signals applied thereto;
• a first sensor, disposed with the anti-noise field, for generating a residual signal indicative of the sum of ambient sounds and anti-noise impinging on the sensor;
• a processor for generating the drive signals to the sound generator in accordance with said residual signal;
• the first sensor cooperating with processor and the sound generator to form a feed back loop producing a feedback signal, wherein the processor generates the drive signals according to a transfer function characteristic of acoustic properties of the feedback loop;
• and
• filter means contained within the processor that filters the feedback signal for selectively varying the transfer function of the system in response to predetermined changes in acoustic conditions indicative of potential instability, wherein the filter means has a transfer characteristic that is not changed by the feedback signal;
• and
• wherein the feedback signal is processed by said processor to form a component of said anti-noise field.

A method for cancelling noise perceived by a user comprising the steps of:

• generating, in accordance with drive signals, an anti-noise field;
• sensing residual noise resulting from interaction of the anti-noise and ambient noise within the anti-noise field;
• generating the drive signals in accordance with said sensed residual noise pursuant to an associated transfer function;
• sensing noise outside the anti-noise field;
• generating indicia of predetermined changes in acoustic conditions indicative of potential instability by comparing a ratio of an internal noise amplitude of the residual noise to an external noise amplitude outside the anti-noise field within a predetermined frequency range to a reference level;
• and
• selectively varying the transfer function in accordance with said indicia.

A method for cancelling noise perceived by a user comprising the steps of:

• generating, in accordance with drive signals, an anti-noise field;
• sensing the residual noise resulting from interaction of the anti-noise and ambient noise within the anti-noise field;
• generating the drive signals in accordance with said sensed residual noise pursuant to an associated transfer function;
• generating indicia of predetermined conditions indicative of potential instability by sensing variations in a ratio between sounds within a predetermined frequency range outside of said anti-noise field to sounds within said predetermined frequency range within said anti-noise field;
• and
• selectively varying the transfer function in accordance with said indicia.

A method for cancelling noise perceived by a user comprising the steps of:

• generating, in accordance with drive signals, an anti-noise field;
• sensing the residual noise resulting form interaction of the anti-noise and ambient noise within the anti-noise field;
• generating the drive signals in accordance with said sensed residual noise pursuant to an associated transfer function, wherein said generating anti-noise and sensing residual noise steps are effected within an earpiece;
• generating indicia of predetermined conditions indicative of potential instability by sensing the pressure against the earpiece;
• and
• selectively varying the transfer function in accordance with said indicia.

An active noise cancelling headset system, comprising:

• a sound generator, disposed with an earpiece, for generating an anti-noise field in response to drive signals applied thereto;
• a first sound sensor, disposed within an anti-noise field, for generating a residual signal indicative of the sum of ambient noise and anti-noise impinging on the sensor;
• a second sound sensor disposed a predetermined distance from said sound generator and output of said anti-noise field to generate a signal indicative of ambient noise;
• and
• a processor, for generating the drive signals to the sound generator in accordance with said residual signal and said signal indicative of said ambient noise;
• filter means contained within the processor that has a transfer characteristics;
• and
• wherein said first sound sensor is connected to cooperate with said processor and said sound generator to form a feedback loop producing a feedback signal, and said second sound sensor is connected to cooperate with said processor and said sound generator to provide feedforward signal noise cancellation, said feedforward and feedback signals being processed by said processor to form a component of said anti-noise field, and
• wherein the feedback signal does not change the transfer characteristic of the filter means.

An active noise cancelling system, comprising:

• a sound generator, responsive to drive signals applied thereto, for generating an anti-noise field;
• a first sound sensor disposed with the anti-noise field to generate a residual signal indicative of the sum of ambient sounds and anti-noise impinging on the sensor;
• a second sound sensor disposed a predetermined distance from said sound source and outside of said noise field to generate a signal indicative of ambient noise;
• a noise cancellation processor having a transfer characteristics, for generating the drive signals to the sound generator;
• the first sensor being connected to cooperate with the processor and the sound generator to form a feed back loop producing a feedback signal;
• and
• the second sensor being connected to cooperate with the processor and the sound generator to provide feedforward signal noise cancellation;
• wherein the noise cancellation processor processes the feedforward signal and the feedback signal to form a component of said anti-noise field and wherein the feedback signal does not modify the transfer characteristics of the noise cancellation processor.

An active noise cancelling system comprising:

• a sound generator, responsive to drive signals applied thereto, for generating an anti-noise field;
• a first sound sensor disposed within said anti-noise field to generate a residual signal indicative of the sum of ambient sounds and anti-noise impinging on the sensor;
• a noise cancellation processor, for generating the drive signals to the sound generator;
• and
• means for generating indicia of conditions indicative of reduced power needs of the system and responsively varying the transfer function of the system in response said indicia.

A method for conserving power in an active noise cancelling system, the method comprising the steps of:

• generating, in accordance with drive signals, an anti-noise field;
• sensing the residual noise resulting from interaction of the anti-noise and ambient noise within the anti-noise field;
• generating the drive signals in accordance with said sensed residual noise;
• generating indicia of the amplitude of ambient noise;
• and
• selectively varying the level of power applied to portions of a processor of the system in accordance with said indicia of amplitude of ambient noise.

A method for cancelling noise perceived by a user comprising the steps of:

• generating, in accordance with drive signals, an anti-noise field centered at a location proximate to the users ear;
• sensing the residual noise resulting from superposition of the anti-noise and ambient noise at an optimal location radially offset from the center of the anti-noise field in accordance with a plurality of acoustic parameters at the user's eardrum to simulate noise cancellation conditions at the user's eardrum, wherein at the optimal location the amplitude of the anti-noise is diminished and wherein the plurality of acoustic parameters include, but are not limited to, the distance of a sound generator from the user's eardrum and the size of an inner cavity at the user's ear;
• and
• generating the drive signals in accordance with said sensed residual noise.

A method for increasing the stability of an active noise cancelling system comprising a noise cancellation circuit, a sound sensor and sound generator cooperating in a feedback loop, the feedback loop having an associated transfer function, the transfer function with respect to components of ambient noise within a predetermined range of frequencies tending to vary with approaching instability of the system, the method including the steps of:

• generating, in accordance with drive signals, an anti-noise field;
• sensing the residual noise resulting from interaction of the anti-noise and ambient noise;
• generating the drive signals in accordance with said sensed residual noise;
• sensing variations in the transfer function of the system with respect to components of ambient noise within said predetermined range of frequencies;
• and
• varying the transfer function of the system in accordance with said sensed variations, wherein varying the transfer function of the system does not vary a transfer function of a filter means that varies the transfer function of the system.

A method for increasing the stability of an active noise cancelling system comprising a noise cancellation circuit, a sound sensor and sound generator cooperating in a feedback loop, the feedback loop having an associated transfer function, the transfer function with respect to components of ambient noise within a predetermined range of frequencies tending to vary with approaching instability of the system, the method including the steps of:

• generating, in accordance with drive signals, an anti-noise field;
• sensing the residual noise resulting from interaction of the anti-noise and ambient noise;
• generating the drive signals in accordance with said sensed residual noise;
• sensing variations in the transfer function of the system with respect to components of ambient noise within said predetermined range of frequencies by determining the ratio of the amplitude of components of ambient noise within said predetermined range of frequencies at a location outside of said noise field and components within said predetermined range of frequencies at a location within said noise field;
• and
• varying the transfer function of the system in accordance with said sensed variations by reducing the gain of the system in response to the ratio of the signals exceeding a predetermined threshold value.

An active noise cancelling system, comprising:

• a sound generator for generating an anti-noise field in response to drive signals applied thereto;
• a first sensor, disposed with the anti-noise field, for generating a residual signal indicative of the sum of ambient sounds and anti-noise impinging on the sensor;
• a processor for generating the drive signals to the sound generator in accordance with said residual signal;
• the first sensor cooperating with processor and the sound generator to form a feed back loop producing a feedback signal, wherein the processor generates the drive signals according to a transfer function characteristic of acoustic properties of the feedback loop;
• and
• filter means contained within the processor that filter the feedback signal for selectively varying the transfer function of the system in response to predetermined changes in acoustic conditions indicative of potential instability, wherein the filter means for selectively varying the transfer function of the system in response to predetermined conditions indicative of potential instability comprises:
• at least one switchable element capable of changing state when the pressure of an earpiece against a user's head is sensed to be outside a predetermined range of acceptable pressure;
• and
• wherein the feedback signal is processed by said processor to form a component of said anti-noise field.

An active noise cancelling system, comprising:

• a sound generator for generating an anti-noise field in response to drive signals applied thereto;
• a first sensor, disposed with the anti-noise field, for generating a residual signal indicative of the sum of ambient sounds and anti-noise impinging on the sensor;
• a processor for generating the drive signals to the sound generator in accordance with said residual signal;
• the first sensor cooperating with processor and the sound generator to form a feed back loop producing a feedback signal, wherein the processor generates the drive signals according to a transfer function characteristic of acoustic properties of the feedback loop;
• and
• filter means contained within the processor that filter the feedback signal for selectively varying the transfer function of the system in response to predetermined changes in acoustic conditions indicative of potential instability, wherein the filter means comprises:
• a gain control circuit comprising at least one element capable of changing the gain of the feedback loop, wherein said control circuit comprises at least one switchable element to change the gain of the feedback loop;
• and
• wherein the feedback signal is processed by said processor to form a component of said anti-noise field.

An active noise cancelling system, comprising:

• a sound generator for generating an anti-noise field in response to drive signals applied thereto;
• a first sensor, disposed with the anti-noise field, for generating a residual signal indicative of the sum of ambient sounds and anti-noise impinging on the sensor;
• a processor for generating the drive signals to the sound generator in accordance with said residual signal;
• the first sensor cooperating with processor and the sound generator to form a feed back loop producing a feedback signal, wherein the processor generates the drive signals according to a transfer function characteristic of acoustic properties of the feedback loop;
• and
• filter means contained within the processor that filter the feedback signal for selectively varying the transfer function of the system in response to predetermined changes in acoustic conditions indicative of potential instability, wherein the filter means comprises:
• a gain control circuit comprising at least one element capable of changing the gain of the feedback loop, wherein said control circuit comprises at least one pressure transducer element to change the gain of the feedback loop;
• and
• wherein the feedback signal is processed by said processor to form a component of said anti-noise field.

An active noise cancelling system, comprising:

• a sound generator for generating an anti-noise field in response to drive signals applied thereto;
• a first sensor, disposed with the anti-noise field, for generating a residual signal indicative of the sum of ambient sounds and anti-noise impinging on the sensor;
• a processor for generating the drive signals to the sound generator in accordance with said residual signal;
• the first sensor cooperating with processor and the sound generator to form a feed back loop producing a feedback signal, wherein the processor generates the drive signals according to a transfer function characteristic of acoustic properties of the feedback loop;
• filter means contained within the processor that filter the feedback signal for selectively varying the transfer function of the system in response to predetermined changes in acoustic conditions indicative of potential instability;
• means for selectively deactivating one or more portions of a controller of said processor to control power supplied to said processor, and
• wherein the feedback signal is processed by said processor to form a component of said anti-noise field.