Ambient noise-reduction system
AssigneeWolfson Microelectronics plc
InventorAlastair Sibbald
Life of this patent
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Abstract
A signal processing circuit is intended for use in a noise reduction system, which produces a target filter characteristic that would achieve optimal noise cancellation, the target filter characteristic including a resonant peak at a first frequency. The signal processing circuit comprises an analogue filter, which has an amplitude response that has a peak or trough at a center frequency, and has a phase response that switches polarity at the center frequency and tends to zero with increase or reduction in frequency away from the center frequency. The center frequency in the amplitude response is substantially equal to the first frequency. The analogue filter may be in the form of a series inductive-capacitive-resistive circuit, where the inductive component is in the form of a gyrator.
Claims21
Signal processing circuitry, for an ambient noise-reduction system for use in a sound reproduction system, producing a target filter characteristic required to provide optimal noise cancellation over a predetermined frequency band, the target filter characteristic including a resonant peak at a first frequency, the signal processing circuitry comprising:
- an analogue filter, having an amplitude response that has a peak or trough at a center frequency, and a phase response that switches polarity at the center frequency and tends to zero with increase or reduction in frequency away from the center frequency, wherein the center frequency in the amplitude response is substantially equal to the first frequency.
An ambient noise reduction system, comprising:
- a microphone for converting ambient acoustic noise into electrical signals,
- signal processing circuitry, for inverting and filtering the electrical signals, and
- an acoustic generator, for converting the inverted and filtered electrical signals into an acoustic signal,
- wherein the ambient noise-reduction system produces a target filter characteristic required to provide optimal noise cancellation over a predetermined frequency band, the target filter characteristic including a resonant peak at a first frequency, and
- wherein the signal processing circuitry comprises an analogue filter, having an amplitude response that has a peak or trough at a center frequency, and a phase response that switches polarity at the center frequency and tends to zero with increase or reduction in frequency away from the center frequency, wherein the center frequency in the amplitude response is substantially equal to the first frequency.
A sound reproduction system, comprising an ambient noise reduction system, wherein the ambient noise reduction system comprises:
- a microphone for converting ambient acoustic noise into electrical signals,
- signal processing circuitry, for inverting and filtering the electrical signals, and
- an acoustic generator, for converting the inverted and filtered electrical signals into an acoustic signal,
- wherein the ambient noise-reduction system produces a target filter characteristic required to provide optimal noise cancellation over a predetermined frequency band, the target filter characteristic including a resonant peak at a first frequency, and
- wherein the signal processing circuitry comprises an analogue filter, having an amplitude response that has a peak or trough at a center frequency, and a phase response that switches polarity at the center frequency and tends to zero with increase or reduction in frequency away from the center frequency, wherein the center frequency in the amplitude response is substantially equal to the first frequency.
Dependencies are inferred from the claim text.