Active acoustic attenuation system with differential filtering

Details Active acoustic attenuation system with differential filtering Active acoustic attenuation system with differential filtering

1988-05-04

1989-06-06

Isen, Forester W.

Electrical audio signal processing systems and devices

Acoustical noise or sound cancellation

Adjacent ear

381 94, G10K 1116

Patent

active

048378348

ABSTRACT:
An adaptive active acoustic attenuation system is provided with extended frequency range to attenuate undesired noise which was previously filtered out to avoid instability of the adaptive model. The input signal from the input microphone to the model and the error signal from the error microphone to the model are differentially bandpass filtered to provide a narrower frequency range error signal. In one embodiment, the model operates in its stable region to provide accurate well behaved correction signals to the cancelling loudspeaker, while still receiving a low frequency input noise signal from the input microphone including frequencies below such range. Minimum attenuation frequency has been reduced by at least an octave.

REFERENCES:
patent: 4480333 (1984-10-01), Ross
patent: 4665549 (1987-05-01), Eriksson et al.
patent: 4677676 (1987-06-01), Eriksson
patent: 4677677 (1987-06-01), Eriksson
patent: 4736431 (1988-04-01), Allie et al.
M. A. Swinbanks, "The Active Control of Sound Propagation in Long Ducts", Journal of Sound and Vibration, (1973), 27(3), 411-436.
B. A. Brown et al., VLSI Systems Design for Digital Signal Processing, vol. I: Signal Processing and Signal Processors, Prentice-Hall, Inc., Englewood Cliffs, N.J., p. 11.

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