US5388160A
Expired / Lapsed
US
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Noise suppressor
Assignee: Panasonic Holdings Corp
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Filing: 1992-06-08
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Granted: 1995-02-07
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Expires: 2012-06-08
Abstract
Abstract In a noise suppressor, a noise signal detected by a first detector is inputted to an adaptive filter and a FIR filter. An output signal of the adaptive filter is reproduced by a speaker. The signal reproduced by the speaker and a noise signal from a noise source are detected by a second detector. The signal detected by the second detector is band-limited by a filter circuit and sent to a LMS computing circuit. The LMS computing circuit updates a coefficient of the adaptive filter so as to minimize an output signal of the filter circuit in response to an output signal of the FIR filter and an output signal of the filter circuit.
Inventors
- 👤 Hiroyuki Hashimoto
- 👤 Kenichi Terai
- 👤 Yasutoshi Nakama
- 👤 Hironari Ogata
- 👤 Chie Yano
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 06:22
CPC Classifications
G; G10; G10K; G10K11/00; G10K11/16; G10K11/175; G10K11/178; G10K11/1787; G10K11/17879; G10K11/17881; G10K11/1781; G10K11/17813; G10K11/17817; G10K11/17821; G10K11/17825; G10K11/1783; G10K11/1785; G10K11/17853; G10K11/17854; G10K2210/00; G10K2210/30; G10K2210/301; G10K2210/3012; G10K2210/3028; G10K2210/3045
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
254 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said filter circuit including said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a coherence computing circuit for computing a coherence of the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is activated; a Hilbert computing circuit for performing a Hilbert operation by an output signal from said coherence computing circuit; and a signal processor for processing the noise signal inputted thereto by a coefficient set by an output signal of said Hilbert computing circuit when the noise control is activated.
Claim 2
Dependent Claim
254 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said filter circuit including said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a coherence computing circuit for computing a coherence of the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is activated; a Hilbert computing circuit for performing a Hilbert operation by an output signal from said coherence computing circuit; and a signal processor for processing the noise signal inputted thereto by a coefficient set by an output signal of said Hilbert computing circuit when the noise control is activated.
Claim 3
Dependent Claim
186 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said filter circuit including said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit comprises: a whitening circuit for computing a characteristic for flattening a frequency spectrum of the noise signal detected by said second detector; and a first signal processor for processing the noise signal detected by said second detector using the characteristic computed by said whitening circuit as a filter coefficient.
Claim 4
Dependent Claim
186 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said filter circuit including said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit comprises: a whitening circuit for computing a characteristic for flattening a frequency spectrum of the noise signal detected by said second detector; and a first signal processor for processing the noise signal detected by said second detector using the characteristic computed by said whitening circuit as a filter coefficient.
Claim 5
Dependent Claim
238 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said filter circuit including said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a correlation computing circuit for computing a correlation function between the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is activated; and a signal processor operative when the noise control is activated for processing the noise signal inputted thereto using a coefficient set by an output signal of said correlation computing circuit.
Claim 6
Dependent Claim
238 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said filter circuit including said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a correlation computing circuit for computing a correlation function between the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is activated; and a signal processor operative when the noise control is activated for processing the noise signal inputted thereto using a coefficient set by an output signal of said correlation computing circuit.
Claim 7
Dependent Claim
238 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a filter circuit for processing an output signal of said adaptive filter; a speaker responsive to an output signal of said filter circuit for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said filter circuit through said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a correlation computing circuit for computing a correlation function between the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is activated; and a signal processor operative when the noise control is activated for processing the noise signal inputted thereto using a coefficient set by an output signal of said correlation computing circuit.
Claim 8
Dependent Claim
238 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a filter circuit for processing an output signal of said adaptive filter; a speaker responsive to an output signal of said filter circuit for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said filter circuit through said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a correlation computing circuit for computing a correlation function between the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is activated; and a signal processor operative when the noise control is activated for processing the noise signal inputted thereto using a coefficient set by an output signal of said correlation computing circuit.
Claim 9
Dependent Claim
234 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; a filter circuit for processing the noise signal detected by said first detector; an adaptive filter for processing an output signal of said filter circuit; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the noise signal from said filter circuit by using a coefficient substantially equivalent to a transfer function from said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a correlation computing circuit for computing a correlation function between the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is activated; and a signal processor operative when the noise control is activated for processing the noise signal inputted thereto using a coefficient set by an output signal of said correlation computing circuit.
Claim 10
Dependent Claim
234 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; a filter circuit for processing the noise signal detected by said first detector; an adaptive filter for processing an output signal of said filter circuit; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the noise signal from said filter circuit by using a coefficient substantially equivalent to a transfer function from said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a correlation computing circuit for computing a correlation function between the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is activated; and a signal processor operative when the noise control is activated for processing the noise signal inputted thereto using a coefficient set by an output signal of said correlation computing circuit.
Claim 11
Dependent Claim
172 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said filter circuit including said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit has a frequency characteristic with respect to a frequency spectrum of the noise signal detected by said second detector so as to flatten the frequency spectrum of the noise signal detected by said second detector.
Claim 12
Dependent Claim
172 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said filter circuit including said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit has a frequency characteristic with respect to a frequency spectrum of the noise signal detected by said second detector so as to flatten the frequency spectrum of the noise signal detected by said second detector.
Claim 13
Dependent Claim
182 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector, a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said filter circuit including said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit has such a characteristic that cuts off only frequency bands in which the noise signal detected by said first detector and the noise signal detected by said second detector have a weak correlation to each other in a frequency range controllable by said adaptive filter.
Claim 14
Dependent Claim
182 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector, a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said filter circuit including said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit has such a characteristic that cuts off only frequency bands in which the noise signal detected by said first detector and the noise signal detected by said second detector have a weak correlation to each other in a frequency range controllable by said adaptive filter.
Claim 15
Dependent Claim
182 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a filter circuit for processing an output signal of said adaptive filter, a speaker responsive to an output signal of said filter circuit for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said filter circuit through said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that cuts off only frequency bands in which the noise signal detected by said first detector and the noise signal detected by said second detector have a weak correlation to each other in a frequency range controllable by said adaptive filter.
Claim 16
Dependent Claim
182 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a filter circuit for processing an output signal of said adaptive filter, a speaker responsive to an output signal of said filter circuit for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said filter circuit through said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that cuts off only frequency bands in which the noise signal detected by said first detector and the noise signal detected by said second detector have a weak correlation to each other in a frequency range controllable by said adaptive filter.
Claim 17
Dependent Claim
178 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; a filter circuit for processing the noise signal detected by said first detector, an adaptive filter for processing an output signal of said filter circuit; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the output signal from said filter circuit by using a coefficient substantially equivalent to a transfer function from said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that cuts off only frequency bands in which the noise signal detected by said first detector and the noise signal detected by said second detector have a weak correlation to each other in a frequency range controllable by said adaptive filter.
Claim 18
Dependent Claim
178 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; a filter circuit for processing the noise signal detected by said first detector, an adaptive filter for processing an output signal of said filter circuit; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the output signal from said filter circuit by using a coefficient substantially equivalent to a transfer function from said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that cuts off only frequency bands in which the noise signal detected by said first detector and the noise signal detected by said second detector have a weak correlation to each other in a frequency range controllable by said adaptive filter.
Claim 19
Dependent Claim
254 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a filter circuit for processing an output signal of said adaptive filter; a speaker responsive to an output signal of said filter circuit for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said filter circuit through said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a coherence computing circuit for computing a coherence of the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is acted; a Hilbert computing circuit for performing a Hilbert operation by an output signal from said coherence computing circuit; and a signal processor for processing the noise signal inputted thereto by a coefficient set by an output signal of said Hilbert computing circuit when the noise control is acted.
Claim 20
Dependent Claim
254 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a filter circuit for processing an output signal of said adaptive filter; a speaker responsive to an output signal of said filter circuit for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said filter circuit through said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a coherence computing circuit for computing a coherence of the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is acted; a Hilbert computing circuit for performing a Hilbert operation by an output signal from said coherence computing circuit; and a signal processor for processing the noise signal inputted thereto by a coefficient set by an output signal of said Hilbert computing circuit when the noise control is acted.
Claim 21
Dependent Claim
250 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; a filter circuit for band-limiting the noise signal detected by said first detector; an adaptive filter for processing an output signal of said filter circuit; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a coherence computing circuit for computing a coherence of the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is acted; a Hilbert computing circuit for performing a Hilbert operation by an output signal from said coherence computing circuit; and a signal processor for processing the noise signal inputted thereto by a coefficient set by an output signal of said Hilbert computing circuit when the noise control is acted.
Claim 22
Dependent Claim
250 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; a filter circuit for band-limiting the noise signal detected by said first detector; an adaptive filter for processing an output signal of said filter circuit; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to the noise signal detected by said second detector and an output signal of said digital filter, wherein said filter circuit has such a characteristic that passes only a frequency band in which there is a strong correlation between the noise signal detected by said first detector and the noise signal detected by said second detector, and comprises: a coherence computing circuit for computing a coherence of the noise signal detected by said first detector and the noise signal detected by said second detector before a noise control is acted; a Hilbert computing circuit for performing a Hilbert operation by an output signal from said coherence computing circuit; and a signal processor for processing the noise signal inputted thereto by a coefficient set by an output signal of said Hilbert computing circuit when the noise control is acted.
Claim 23
Dependent Claim
235 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit comprises: a whitening circuit for computing a characteristic for flattening a frequency spectrum of the noise signal detected by said second detector; a first signal processor for processing the noise signal detected by said second detector using the characteristic computed by said whitening circuit as a filter coefficient to obtain an error signal used for updating the coefficient of said adaptive filter; and a second signal processor for processing the output signal of said digital filter using the same filter coefficient as that of said first signal processor to obtain a reference signal used for updating the coefficient of said adaptive filter.
Claim 24
Dependent Claim
235 words
A noise suppressor comprising: a first detector for detecting a noise signal from a noise source; an adaptive filter for processing the noise signal detected by said first detector; a speaker responsive to an output signal of said adaptive filter for reproducing a sound; a second detector for detecting a noise signal at a predetermined evaluating point; a filter circuit for processing the noise signal detected by said second detector; a digital filter for processing the noise signal from said first detector by using a coefficient substantially equivalent to a transfer function from said speaker to said second detector; and a coefficient updating circuit for controlling a coefficient of said adaptive filter according to an output signal of said filter circuit and an output signal of said digital filter, wherein said filter circuit comprises: a whitening circuit for computing a characteristic for flattening a frequency spectrum of the noise signal detected by said second detector; a first signal processor for processing the noise signal detected by said second detector using the characteristic computed by said whitening circuit as a filter coefficient to obtain an error signal used for updating the coefficient of said adaptive filter; and a second signal processor for processing the output signal of said digital filter using the same filter coefficient as that of said first signal processor to obtain a reference signal used for updating the coefficient of said adaptive filter.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1998-02-06 | 1998-08-08 | 1999-02-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-02-06 | 2002-08-08 | 2003-02-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-02-06 | 2006-08-08 | 2007-02-07 | $7700.00 | Window Closed / Lapsed |