Acoustic feedback cancellation for equalized amplifying systems
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United States of America Patent
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Jul 2, 1996
Grant Date -
N/A
app pub date -
Feb 1, 1994
filing date -
Feb 1, 1994
priority date (Note) -
Expired
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Abstract
A speaker amplification system incorporates an adaptable notch filter that can dynamically adapt to the frequency of feedback oscillations caused by acoustic feedback frequency in order to remove the feedback oscillation before they are amplified above an audible level. The adaptable notch filter is implemented as an adaptable finite impulse response filter by means of a digital signal processor. The finite impulse response filter also has an adaptable convergence factor which minimizes noise introduced by the filter. A special limiting routine is used to limit the values of the finite impulse response filter coefficients to prevent the filter from 'blowing up' due to large input signal disturbances. The speaker amplification system also includes circuitry which provides multiple bands of equalization, with each band being capable of amplification. The mullet-band equalizer function allows hearing impaired people to adjust the frequency response of the telephones handset speaker, to provide better intelligibility, due to a large increase in volume over normal telephone handset receivers.
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