US4087633A
Expired / Lapsed
US
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Dereverberation system
Assignee: AT&T Inc
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Filing: 1977-07-18
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Granted: 1978-05-02
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Expires: 1997-07-18
Abstract
Abstract Disclosed is a signal dereverberation system employing two spatially separated microphones. The microphones' signals are processed by first equalizing the delay in the signals applied to the microphones, and following the delay equalization, the signal magnitude of the two microphones is equalized and compared at short intervals in a coincidence circuit. Signals that are within a predetermined percentage tolerance of each other are utilized, while signals outside the predetermined tolerance are inhibited. The output signal of the coincidence circuit is filtered to remove out-of-band signals introduced by the switching within the coincidence circuit. Processing of the microphones' signals can be performed in a single processor, covering the entire signal band; or in a plurality of processors, each independently processing a different band of the signal. When a plurality of processors is employed, the output signals of the plurality of coincidence circuit (one in each processor) are appropriately filtered and combined to form the desired nonreverberant signal.
Inventors
- 👤 James William Fitzwilliam
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 14:35
CPC Classifications
H; H04; H04R; H04R29/00; H04R29/004; H04R29/005; H04R29/006; H04R3/00; H04R3/005; H04R2201/00; H04R2201/40; H04R2201/403
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
95 words
A dereverberation system including a first and second microphone for developing a nonreverberant bandpass signal comprising: first means, responsive to said first and second microphones, for equalizing the delay of the signal of said first microphone with respect to the signal of said second microphone; second means, responsive to said first means, for equalizing the amplitude of the signal of said first microphone with respect to the signal of said second microphone; third means for inhibiting noncoincident output signals of said second means; and fourth means for filtering the output signal of said third means.
Claim 2
Dependent Claim
95 words
A dereverberation system including a first and second microphone for developing a nonreverberant bandpass signal comprising: first means, responsive to said first and second microphones, for equalizing the delay of the signal of said first microphone with respect to the signal of said second microphone; second means, responsive to said first means, for equalizing the amplitude of the signal of said first microphone with respect to the signal of said second microphone; third means for inhibiting noncoincident output signals of said second means; and fourth means for filtering the output signal of said third means.
Claim 3
Dependent Claim
143 words
A dereverberation system including a plurality of signal processors responsive, in parallel, to a first and second microphone and developing nonreverberant bandpass signals combined in a summing network to develop a single nonreverberant signal, each of said signal processors comprising: first means for selecting a frequency band in the signals of said first and second microphones; second means, responsive to said first means, for equalizing the delay of the signal of said first microphone with respect to the signal of said second microphone; third means, responsive to said second means, for equalizing the amplitude of the signal of said first microphone with respect to the signal of said second microphone; fourth mean for inhibiting noncoincident output signals of said third means; and fifth means, responsive to said fourth means, for selecting a frequency band corresponding to the band selected by said first means.
Claim 4
Dependent Claim
143 words
A dereverberation system including a plurality of signal processors responsive, in parallel, to a first and second microphone and developing nonreverberant bandpass signals combined in a summing network to develop a single nonreverberant signal, each of said signal processors comprising: first means for selecting a frequency band in the signals of said first and second microphones; second means, responsive to said first means, for equalizing the delay of the signal of said first microphone with respect to the signal of said second microphone; third means, responsive to said second means, for equalizing the amplitude of the signal of said first microphone with respect to the signal of said second microphone; fourth mean for inhibiting noncoincident output signals of said third means; and fifth means, responsive to said fourth means, for selecting a frequency band corresponding to the band selected by said first means.
Claim 5
Dependent Claim
79 words
A speech dereverberation system including two microphones connected to a signal processor characterized by: first means for equalizing the time delay between the signals of said two microphones applied to said signal processor to develop two delay-equalized signals; second means for equalizing amplitudes of said two delay-equalized signals to develop two delay and amplitude-equalized signals; and third means for selecting time intervals of said two delay and amplitude-equalized signals which are within preselected percentage amplitude tolerance of each other.
Claim 6
Dependent Claim
79 words
A speech dereverberation system including two microphones connected to a signal processor characterized by: first means for equalizing the time delay between the signals of said two microphones applied to said signal processor to develop two delay-equalized signals; second means for equalizing amplitudes of said two delay-equalized signals to develop two delay and amplitude-equalized signals; and third means for selecting time intervals of said two delay and amplitude-equalized signals which are within preselected percentage amplitude tolerance of each other.
Claim 7
Dependent Claim
98 words
A speech dereverberation system including two microphones connected to a plurality of signal processors and a summing network responsive to the output signals of said signal processors, said signal processors being characterized by: first means for equalizing the time delay between the signals of said two microphones applied to said signal processor to develop two delay-equalized signals; second means for equalizing amplitudes of said two delay-equalized signals to develop two delay and amplitude-equalized signals; and third means for selecting time intervals of said two delay and amplitude-equalized signals which are within preselected percentage amplitude tolerance of each other.
Claim 8
Dependent Claim
98 words
A speech dereverberation system including two microphones connected to a plurality of signal processors and a summing network responsive to the output signals of said signal processors, said signal processors being characterized by: first means for equalizing the time delay between the signals of said two microphones applied to said signal processor to develop two delay-equalized signals; second means for equalizing amplitudes of said two delay-equalized signals to develop two delay and amplitude-equalized signals; and third means for selecting time intervals of said two delay and amplitude-equalized signals which are within preselected percentage amplitude tolerance of each other.
Claim 9
Dependent Claim
69 words
A signal dereverberation system as in claim 4, further characterized by: fourth means interposed between said two microphones and said first means for passing a preselected frequency band of said signals of said two microphones to said first means; and fifth means, for passing to said summing network those portions of the output signal of said third means which occupy said predetermined frequency band passed by said fourth means.
Claim 10
Dependent Claim
70 words
The system of claim 5 wherein said first means comprises: fixed delay means responsive to one of he microphones' signals passed by said fourth means; variable delay means responsive to the other of the microphones' signals passed by said fourth means; and delay control means responsive to the output signals of said fixed delay means and said variable delay means for controlling the delay provided by said variable delay means.
Claim 11
Dependent Claim
24 words
The system of claim 6 wherein said fixed delay means and said variable delay means are each preceded by means for sampling applied signals.
Claim 12
Dependent Claim
19 words
The system of claim 6 wherein said fixed delay means and said variable delay means employ CCD shift registers.
Claim 13
Dependent Claim
30 words
The system of claim 6 wherein said delay control means maximizes a sum signal developed by adding the output signals of said fixed delay means and said variable delay means.
Claim 14
Dependent Claim
75 words
The system of claim 5 wherein said second means comprises: a fixed gain stage responsive to one of said two delay-equalized signals of said second means; a variable gain stage responsive to the other of said two delay-equalized signals of said second means; and gain control means responsive to the output signal of said fixed gain stage and the output signal of said variable gain stage for controlling the gain of said variable gain stage.
Claim 15
Dependent Claim
30 words
The system of claim 10 wherein said gain control means controls said variable gain stage to equalize the amplitudes of the outputs signals of said fixed and variable gain stages.
Claim 16
Dependent Claim
37 words
The system of claim 10 wherein said gain control means affects said variable gain stage to minimize the difference between the output signal of said variable gain stage and the output signal of said fixed gain stage.
Claim 17
Dependent Claim
13 words
The system of claim 5 wherein said third means comprises a coincidence circuit.
Claim 18
Dependent Claim
110 words
The system of claim 5 wherein said third means comprises: fifth mean fo developing a difference signal corresponding to the difference between said two delay and amplitude-equalized signals of said second means; sixth means for developing a magnitude of said difference signal; seventh means for comparing the output signal of said sixth means to a prechosen threshold level which is a function of the signal levels of one or both of said delay and amplitude-equalized signals of said second means; and eighth mean, responsive to said two delay and amplitude-equalized signals of said second means, for developing an output signal of said third means under control of said seventh means.
Claim 19
Dependent Claim
112 words
The system of claim 5 wherein said third means comprises: fifth means for developing a difference signal corresponding to the difference between said two delay and amplitue-equalized signals of said second means; sixth means for developing a magnitude of said difference signal; seventh means for comparing the output signal of said sixth means to a prechosen threshold level which is a function of the signal levels of one or both of said delay and amplitude-equalized signals of said second means; and eighth means, responsive to one of said two delay and amplitude-equalized signals of said second means for developing an output signal of said third means under control of said seventh means.
Claim 20
Dependent Claim
113 words
The system of claim 5 wherein said third means comprises: fifth means for developing a difference signal corresponding to the difference between said two delay and amplitude-equalized signals of said second means; sixth means for developing a magnitude of said difference signal; seventh means for comparing the output signal of said sixth means to a prechosen threshold level which is a function of the signal levels of one or both of said delay and amplitude-equalized signals of said second means; and eighth means, responsive to an average of said two delay and amplitude-equalized signals of said second means, for developing an output signal of said third means under control of said seventh means.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-05-01 | 1981-10-31 | 1982-05-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-05-01 | 1985-10-31 | 1986-05-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-05-01 | 1989-10-31 | 1990-05-02 | $7700.00 | Window Closed / Lapsed |