Noise suppressor

• US 5,131,047 A
• Filed: 06/07/1991
• Issued: 07/14/1992
• Est. Priority Date: 06/11/1990
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Suzuki, Tomokazu, Kenichi, Terai, Yasutoshi, Nakama, Ryoji, Suzuki, Hashimoto, Hiroyuki
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): Chiang, Jack
• Application Number:
  US07/712,038
• Time in Patent Office: 403 Days
• Field of Search: 381/13, 381/86, 381/71, 381/73.1, 381/93, 381/94
• US Class Current: 381/71.11
• CPC Class Codes: G10K 11/17821 characterised by the analysis of the input signals only
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/17827 Desired external signals, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 11/1783 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 11/17885 additionally using a desired external signal, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 2210/1053 Hi-fi, i.e. anything involving music, radios or loudspeakers
• CPC Class Codes: G10K 2210/108 Communication systems, e.g. where useful sound is kept and noise is cancelled
• CPC Class Codes: G10K 2210/1282 Automobiles
• CPC Class Codes: G10K 2210/3041 Offline
• CPC Class Codes: G10K 2210/3045 Multiple acoustic inputs, single acoustic output
• CPC Class Codes: G10K 2210/3225 Radio or other sources used in ANC for transfer function estimation; Means to avoid interference between desired signals, e.g. from a car stereo, and the ANC signal
• CPC Class Codes: G10K 2210/503 Diagnostics; Stability; Alarms; Failsafe
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

A noise suppressor is disclosed in which a noise signal is detected by a first detector, then processed by an adaptive filter, and an output signal from the adaptive filter and an audio signal from audio equipment are added by an adder and reproduced by a speaker. The sound signal thus reproduced by the speaker and the noise signal are detected by a second detector located at a listening point and sent to a filter control circuit. The filter control circuit possesses the signal sent from the second detector and the audio signal from the audio equipment having a transfer function from the adder to the filter control circuit convoluted thereby to remove the audio signal component therefrom. The adaptive filter adaptively controls the noise signal in response to the output signal from the filter control circuit.

Claims

1. A noise suppressor comprising:

a first detector for detecting a noise or a vibration of a noise source;

an adaptive filter for processing a noise signal detected by said first detector;

an adder for adding an output signal from said adaptive filter and an audio signal outputted from audio equipment;

a speaker for reproducing an output signal from said adder;

a second detector for detecting a sound signal at a listening point;

a digital filter for processing an audio signal outputted from said audio equipment; and

a filter control circuit for processing a signal detected by said second detector and an output signal from said digital filter for controlling said adaptive filter and said digital filter.

2. A noise suppressor as claimed in claim 1, wherein said digital filter approximates a transfer function from said adder to said filter control circuit.

3. A noise suppressor as claimed in claim 1, wherein said digital filter is another adaptive filter.

4. A noise suppressor as claimed in claim 3, wherein said filter control circuit comprises:

a computing circuit for computing a signal detected by said second detector and an output signal from said another adaptive filter; and

a switching circuit for selecting a signal thus obtained by said computing circuit to output to either said adaptive filter or said another adaptive filter.

5. A noise suppressor comprising:

a first detector for detecting a noise or a vibration of a noise source;

a first digital filter for processing a noise signal detected by said first detector;

an adder for adding an output signal from said first digital filter and an audio signal from audio equipment;

a speaker for reproducing an output signal from said adder;

a second detector for detecting a sound signal at a listening point;

a second digital filter for processing an audio signal outputted from said audio equipment;

a computing circuit for computing a signal detected by said second detector and an output signal from said second digital filter;

a first switching circuit for effecting switching of an output signal from said first detector and an audio signal from said audio equipment;

a coefficient control circuit for controlling a coefficient of said first digital filter and that of second digital filter in response to an output signal from said first switch circuit and that from said computing circuit; and

a second switching circuit for switching an output signal from said coefficient control circuit to said first and second digital filters.

6. A noise suppressor as claimed in claim 5, wherein when said first switching circuit is switched as to receive an audio signal from said audio equipment and said second switching circuit is switched to said second digital filter, a coefficient of said second digital filter is controlled by said coefficient control circuit, and when said first switching circuit is switched as to receive an output signal from said first detector and said second switching circuit is switched to said first digital filter, a coefficient of said first digital filter is controlled by said coefficient control circuit, thereby effecting a noise suppression.