Patent US4457863A successfully refreshed from Google Patents.
EP0094762A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Automatic time domain equalization of audio signals
Assignee: TDY Industries LLC
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Filing: 1983-05-04
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Granted: —
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Expires: 2003-05-04
Abstract
Abstract An apparatus for modifying the audio response of a sound reproduction system, particularly in the form of an improved audio equalizer comprising a discrete-time filter connected in the sound reproduction system. Means are provided for introducing an electrical test signal into a first point in the sound reproduction system, typically at the input of an electroacoustic transducer. Means, such as a microphone, are provided for detecting at a predetermined location the acoustic output produced by the transducer of the sound reproduction system in response to the test signal. The qualizer includes means for generating a sampled sequence of signals from the detected acoustic output of the sound reproduction system. Means are provided for generating from the sequence of signals, coefficients of the discrete-time filter and the tap locations or time slots of the respective coefficients. Means are also included for storing those coefficients and time slots or locations in appropriate order together with the addresses at which they are stored.
Inventors
- 👤 Robert A. Berkovitz
- 👤 Ronald P. Genereux
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 22:12
CPC Classifications
H; H04; H04R; H04R3/00; H04R3/04; H03; H03G; H03G5/00; H03G5/005; H03G5/16; H03G5/165
Claims Analysis
Total Claims: 49
Claim 1
Independent Claim
83 words
An apparatus for modifying the audio response of a sound reproduction system with respect to the transfer function of at least a selected portion of said system, said apparatus comprising: means for introducing a test signal into the input of said portion; means for detecting at the output of said portion, the test signal as transmitted from said input to said output; means for producing coefficients for a discrete-time filter in accordance with the detected test signal; and means for storing said coefficients.
Claim 2
Independent Claim
83 words
An apparatus for modifying the audio response of a sound reproduction system with respect to the transfer function of at least a selected portion of said system, said apparatus comprising: means for introducing a test signal into the input of said portion; means for detecting at the output of said portion, the test signal as transmitted from said input to said output; means for producing coefficients for a discrete-time filter in accordance with the detected test signal; and means for storing said coefficients.
Claim 3
Dependent Claim
38 words
Apparatus as defined in claim 1 wherein said means for producing coefficients comprises means for generating, responsively to said detected test signal, a corresponding time-sampled sequence of signals; and means programmed to generate said coefficients from said sequence.
Claim 4
Dependent Claim
43 words
Apparatus as defined in claim 2 wherein said means programmed to generate said coefficients comprises digital computer means, said computer means being programmed for discrete-time filtering, in accordance with the stored coefficients, audio signals introduced into said system following production of said coefficients.
Claim 5
Dependent Claim
37 words
Apparatus as defined in claim 2 including discrete-time filter means connected to the output of said oportion for discrete-time filtering, in accordance with the stored coefficients, audio signals introduced into said system following production of said coefficients.
Claim 6
Dependent Claim
15 words
Apparatus as defined in claim 4 wherein said discrete-time filter means is a digital filter.
Claim 7
Dependent Claim
65 words
Apparatus as defined in claim 3 including an electroacoustic transducer; said discrete-time filter means being connected to feed the input of said electroacoustic transducer; said means for producing said coefficients including means for producing responsively to said detected test signal, a corresponding time-sampled sequence of signals; said filter means including digital computer means programmed to generate from said time-sampled sequence, coefficients of said filter means.
Claim 8
Dependent Claim
13 words
Apparatus as defined in claim 6 wherein said transducer is a loudspeaker system.
Claim 9
Dependent Claim
56 words
Apparatus as defined in claim 7 wherein said means for introducing said test signal comprises means for providing an electrical test signal to the input of said loudspeaker system; and means for detecting at a predetermined location relative to said loudspeaker system, the acoustic output produced by said loudspeaker system responsively to said electrical test signal.
Claim 10
Dependent Claim
49 words
Apparatus as defined in claim 8 wherein said means for detecting comprises microphone means for generating at its output electrical signals responsively to the detected acoustic output; and a communications link between the output of said microphone means and the input of said means for producing said time-sampled sequence.
Claim 11
Dependent Claim
40 words
Apparatus as defined in claim 9 wherein said link includes a broadcast portion comprising means for generating a radiant energy beam; and means for converting the electrical signals generated by said microphone means into modulation of said radiant energy beam.
Claim 12
Dependent Claim
23 words
Apparatus as defined in claim 10 wherein said means for converting said electrical signals generated by said microphone means comprises a frequency modulator.
Claim 13
Dependent Claim
38 words
Apparatus as defined in claim 10 including manually operable switching means for connecting a power source to said broadcast portion so as to initiate operation of the latter, said broadcast portion being packaged as a hand-holdable portable unit.
Claim 14
Dependent Claim
18 words
Apparatus as defined in claim 12 including said power source for providing electrical power to said broadcast portion.
Claim 15
Dependent Claim
30 words
Apparatus as defined in claim 10 further including sensor means connected to said loudspeaker means and responsive to said radiant energy beam for converting said modulations into corresponding electrical signals.
Claim 16
Dependent Claim
24 words
Apparatus as defined in claim 14 wherein said radiant energy beam is a beam of light and said sensor means is a photoelectric sensor.
Claim 17
Dependent Claim
17 words
Apparatus as defined in claim 10 wherein said means for generating said light beam comprises an LED.
Claim 18
Dependent Claim
53 words
Apparatus as defined in claim 10 including manually operable means coupled to said microphone means and communications link for initiating generation of said radiant energy beam; and wherein said means for providing said test signal is actuated to provide the latter responsively to detection of said radiant energy beam by said sensor means.
Claim 19
Dependent Claim
18 words
Apparatus as defined in claim 1 including means for providing said test signal as a white noise signal.
Claim 20
Dependent Claim
32 words
Apparatus as defined in claim 1 including means for providing said test signal as a quadratic-residue sequence (S n ) defined by the expression where n = 1,2,3....., and odd prime number.
Claim 21
Dependent Claim
43 words
Apparatus as defined in claim 8 wherein said means for generating said time-sampled sequence includes means for time-sampling the detected acoustic output of said system; means for determining the values of the magnitudes of such time samples; and means for storing said values.
Claim 22
Dependent Claim
38 words
Apparatus as defined in claim 20 wherein said means for determining said values of the magnitudes of said time samples comprises analog-to-digital conversion means, coupled to said means for time-sampling, for converting said time samples into digital signals.
Claim 23
Dependent Claim
49 words
Apparatus as defined in claim 9 including switching means for alternatively connecting the input of said means for producing said time-sampled sequence between (A) a source of said audio signals introduced into said system, and (B) said communications link to receive said electrical signals transmitted from said microphone means.
Claim 24
Dependent Claim
74 words
Apparatus as defined in claim 22 including means operative initially upon provision of said test signal, for actuating said switching means for connecting said electrical signals from said communications link to the input of said means for producing said time-sampled sequence, and operative after generation and storage of said coefficients, for actuating said switching means for connecting said source of said audio signals to said input of said means for producing said time-sampled sequence.
Claim 25
Dependent Claim
81 words
Apparatus as defined in claim 22 including analog-to-digital conversion means, coupled to said means for producing said time-sampled sequence, for converting said sequence into digital signals, and wherein said digital computer means is also programmmed for convolving said digital signals with the stored coefficients, responsively to actuation of said switching means for connecting said source of said audio signals to said input of said means for producing said time-sampled sequence, thereby filtering the digital signals produced by said analog-to-digital conversion means.
Claim 26
Dependent Claim
78 words
Apparatus for modifying the audio response of a reproduction system with respect to the transfer function of at least a selected portion of said system, said apparatus comprising: means for introducing a audio signal into the input of said portion; discrete-time filter means connected to the output of said portion for discrete-time filtering said audio signal; and means for storing coefficients for said filter means, said coefficients being determined in accordance with the transfer function of said portion.
Claim 27
Dependent Claim
78 words
Apparatus for modifying the audio response of a reproduction system with respect to the transfer function of at least a selected portion of said system, said apparatus comprising: means for introducing a audio signal into the input of said portion; discrete-time filter means connected to the output of said portion for discrete-time filtering said audio signal; and means for storing coefficients for said filter means, said coefficients being determined in accordance with the transfer function of said portion.
Claim 28
Dependent Claim
174 words
. An audio equalizer for a loudspeaker system in a preselected listening environment, which system includes filter means connected to the input of said loudspeaker system and adjustable for equalizing the perceived output of said loudspeaker system, means for providing an acoustical test signal at the output of said loudspeaker system, and microphone means for detecting said acoustic test signal at a predetermined location in said environment relative to said loudspeaker system, the improvement wherein said microphone means is contained in a hand-held, battery-operated unit containing also means for generating a radiant energy beam at a frequency higher than the frequencies contained in a bandwidth over which said equalization is to occur; means for converting the output signals generated by said microphone means into modulation of said energy beam; and when radiant energy sensor means are provided connected to said loudspeaker means and responsive to said energy beam for converting said modulations into corresponding electrical signals; and means are provided for adjusting said filter means responsively to said electrical signals to effect said equalizing.
Claim 29
Dependent Claim
174 words
. An audio equalizer for a loudspeaker system in a preselected listening environment, which system includes filter means connected to the input of said loudspeaker system and adjustable for equalizing the perceived output of said loudspeaker system, means for providing an acoustical test signal at the output of said loudspeaker system, and microphone means for detecting said acoustic test signal at a predetermined location in said environment relative to said loudspeaker system, the improvement wherein said microphone means is contained in a hand-held, battery-operated unit containing also means for generating a radiant energy beam at a frequency higher than the frequencies contained in a bandwidth over which said equalization is to occur; means for converting the output signals generated by said microphone means into modulation of said energy beam; and when radiant energy sensor means are provided connected to said loudspeaker means and responsive to said energy beam for converting said modulations into corresponding electrical signals; and means are provided for adjusting said filter means responsively to said electrical signals to effect said equalizing.
Claim 30
Dependent Claim
36 words
An improvement in an audio equalizer as defined in claim 26 wherein said filter means is a discrete-time filter; and wherein said equalizer includes means for generating from said electrical signals, coefficients of said discrete-time filter.
Claim 31
Dependent Claim
42 words
An improvement in an audio equalizer as defined in claim 26 wherein said filter means is a digital discrete-time filter; and wherein said equalizer includes means for generating from said electrical signals, discrete numerical values of the coefficients of said discrete-time filter.
Claim 32
Dependent Claim
51 words
An improvement in an audio equalizer as defined in claim 28, including means for converting said electrical signals to digital signals, and said filter means includes means for convolving said digital signals with a target spectrum to generate coefficients of said discrete-time filter for said perceived output at said predetermined location.
Claim 33
Dependent Claim
40 words
An improvement in an audio equalizer as defined in claim 26 wherein said filter means is a digital filter; and said equalizer includes means for generating from said electrical signals, binary-encoded numerical values of the coefficients of said discrete-time filter.
Claim 34
Dependent Claim
127 words
An audio equalizer for a sound reproduction system including an electroacoustic transducer, said equalizer comprising, in combination: a discrete-time filter disposed in series in a first electrical signal channel connected to feed the input of said electroacoustic transducer; means for introducing a test signal into a first selected point in said first channel; means for detecting at a second selected point in said first channel, the test signal as transmitted from said first to said second point; means for producing responsively to the detected test signal, a corresponding time-sampled sequence of signals; and means for introducing said sequence of signals into said filter; said filter including digital computer means programmed to generate from said detected test signal, coefficients of said filter, and means for storing said coefficients.
Claim 35
Dependent Claim
127 words
An audio equalizer for a sound reproduction system including an electroacoustic transducer, said equalizer comprising, in combination: a discrete-time filter disposed in series in a first electrical signal channel connected to feed the input of said electroacoustic transducer; means for introducing a test signal into a first selected point in said first channel; means for detecting at a second selected point in said first channel, the test signal as transmitted from said first to said second point; means for producing responsively to the detected test signal, a corresponding time-sampled sequence of signals; and means for introducing said sequence of signals into said filter; said filter including digital computer means programmed to generate from said detected test signal, coefficients of said filter, and means for storing said coefficients.
Claim 36
Dependent Claim
29 words
An audio equalizer as defined in claim 31 including a low-pass filter disposed in said first channel for limiting transmission of said first channel to relatively low audio frequencies.
Claim 37
Dependent Claim
36 words
An audio equalizer as defined in claim 32 including a second electrical signal channel connected to feed the input of said transducer and disposed in parallel with said first channel for transmitting reltively high audio frequencies.
Claim 38
Dependent Claim
22 words
An audio equalizer as defined in claim 32 wherein said low pass filter has an upper transmission limit of about one kilohertz.
Claim 39
Independent Claim
90 words
A method of modifying the audio response of a sound reproduction system with respect to the transfer function of at least a selected portion of said system, comprising the steps of: introducing a test signal into the input of said portion; detecting at the output of said portion, the test signal as transmitted from said input to said output; time-sampling the detected test signal and determining the values of the time samples; generating from said values, coefficients of a discrete-time filter for said detected test signal; and storing said coefficients.
Claim 40
Independent Claim
90 words
A method of modifying the audio response of a sound reproduction system with respect to the transfer function of at least a selected portion of said system, comprising the steps of: introducing a test signal into the input of said portion; detecting at the output of said portion, the test signal as transmitted from said input to said output; time-sampling the detected test signal and determining the values of the time samples; generating from said values, coefficients of a discrete-time filter for said detected test signal; and storing said coefficients.
Claim 41
Dependent Claim
21 words
Method as defined in claim 35, wherein said coefficients are generated by use of an adaptive least mean square error algorithm.
Claim 42
Dependent Claim
69 words
Method as defined in claim 36 whereein said algorithm is expressed as and wherein e(n) is the error signal at discrete time n, x(n) is the value of the test signal at discrete time n, cj are the filter coefficients, µ is a scaling coefficient; j is the index, and m is the number of coefficients in the filter to be synthesized, and is chosen to provide sufficient resolution.
Claim 43
Dependent Claim
45 words
Method as defined in claim 35 wherein the zeroth coefficient of said coefficents is set at unity and a predetermined number of said coefficients immediately following said zeroth coefficent are set at zero, thereby to introduce a time delay into the operation of said filter.
Claim 44
Dependent Claim
66 words
Method as defined in claim 35 including the steps of: time-sampling electrical signals to be equalized for said system; converting the time samples of said electrical signals into corresponding digital signals; convolving said digital signals with said stored coefficients so as to generate filtered digital signals; converting said filtered digital signals to analog signals; and reproducing the analog signals as acoustic signals in an electroacoutic transducer.
Claim 45
Dependent Claim
142 words
Method of equalizing in a preselected listening environment, the diffuse field of a loudspeaker system relative to the direct field thereof, said method comprising the steps of detecting at a predetermined location in said environment relative to said loudspeaker system, the direct and diffuse fields of the acoustic output produced by said loudspeaker system responsively to a test signal; generating a digital signal train corresponding to the time-sampled detected acoustic output of said loudspeaker system; generating from said digital signals, coefficients of an adaptive linear predictive filter for said detected acoustic output, the zeroth coefficient of said coefficents being set at minus unity and a predetermined number of said coeffients immediately following said zeroth coefficient being held at zero, said predetermined number being sufficient to prevent the generation of coefficients corresponding to said detection of the direct field in said acoustic output.
Claim 46
Dependent Claim
142 words
Method of equalizing in a preselected listening environment, the diffuse field of a loudspeaker system relative to the direct field thereof, said method comprising the steps of detecting at a predetermined location in said environment relative to said loudspeaker system, the direct and diffuse fields of the acoustic output produced by said loudspeaker system responsively to a test signal; generating a digital signal train corresponding to the time-sampled detected acoustic output of said loudspeaker system; generating from said digital signals, coefficients of an adaptive linear predictive filter for said detected acoustic output, the zeroth coefficient of said coefficents being set at minus unity and a predetermined number of said coeffients immediately following said zeroth coefficient being held at zero, said predetermined number being sufficient to prevent the generation of coefficients corresponding to said detection of the direct field in said acoustic output.
Claim 47
Dependent Claim
192 words
Apparatus for modifying the audio frequency spectrum of a first input signal to a target audio frequency spectrum of a second signal, said apparatus comprising, in combination: first means for modifying the audio response of a first sound reproduction system with respect to the transfer function of at least a selected portion of said first system; said first means including means for introducing a specific test signal with a predetermined spectrum into the input of said selected portion; means for detecting at the output of said selected portion, the test signal as transmitted from said input of said selected portion to said output of said selected portion; means for producing a first set of coefficients for first discrete-time filter means in accordance with the detected test signal; first discrete-time filter means for discrete-time filtering, in accordance with said first set of coefficients, said second signal to produce a signal modified in accordance with said first set of coefficients; said apparatus also including second means for modifying the audio response of a sound reproduction system with respect a specific portion of said second system having the same transfer function; said second means including
Claim 48
Dependent Claim
192 words
Apparatus for modifying the audio frequency spectrum of a first input signal to a target audio frequency spectrum of a second signal, said apparatus comprising, in combination: first means for modifying the audio response of a first sound reproduction system with respect to the transfer function of at least a selected portion of said first system; said first means including means for introducing a specific test signal with a predetermined spectrum into the input of said selected portion; means for detecting at the output of said selected portion, the test signal as transmitted from said input of said selected portion to said output of said selected portion; means for producing a first set of coefficients for first discrete-time filter means in accordance with the detected test signal; first discrete-time filter means for discrete-time filtering, in accordance with said first set of coefficients, said second signal to produce a signal modified in accordance with said first set of coefficients; said apparatus also including second means for modifying the audio response of a sound reproduction system with respect a specific portion of said second system having the same transfer function; said second means including
Claim 49
Dependent Claim
96 words
Claim 41 continued means for introducing said modified signal into the input of said specific portion; means for detecting at the output of said specific portion, said modified signal as transmitted from the input to the output of said specific portion; means for producing a second set of coefficients for second discrete-time filter means in accordance with the detected modified signal; and second discrete-time filter means for discrete-time filtering, in accordance with said second set of coefficients, said first input signal to produce an output signal having the spectral characteristics of said target audio frequency spectrum.
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