US6556685B1 — Companding noise reduction system with simultaneo…

Claim 1

Independent Claim 147 words

A companding noise reduction system for processing sonic frequencies while minimizing distortion thereof, said system comprising: an encoder for compressing an input signal representative of the sonic frequencies to be processed, wherein the encoder includes a first variable gain element which receives the input signal and develops as an output signal a compressed signal which is delivered to a transmission path; a decoder for expanding the compressed signal, wherein the decoder includes a second variable gain element which receives the compressed signal from the transmission path and then develops as an output signal the processed sonic frequencies; and a single feedforward sidechain which is electrically coupled to the encoder and the decoder, wherein a control signal is developed by the single feedforward sidechain in response to the input signal and utilized to thereby control gain of the first variable gain element and the second variable gain element.

Claim 2

Dependent Claim 147 words

A companding noise reduction system for processing sonic frequencies while minimizing distortion thereof, said system comprising: an encoder for compressing an input signal representative of the sonic frequencies to be processed, wherein the encoder includes a first variable gain element which receives the input signal and develops as an output signal a compressed signal which is delivered to a transmission path; a decoder for expanding the compressed signal, wherein the decoder includes a second variable gain element which receives the compressed signal from the transmission path and then develops as an output signal the processed sonic frequencies; and a single feedforward sidechain which is electrically coupled to the encoder and the decoder, wherein a control signal is developed by the single feedforward sidechain in response to the input signal and utilized to thereby control gain of the first variable gain element and the second variable gain element.

Claim 3

Dependent Claim 52 words

The companding noise reduction system as defined in claim 1 wherein the single feedforward sidechain further comprises a level detector for detecting an amplitude of the input signal, wherein the level detector receives the input signal, and wherein the control signal is developed in response to the amplitude of the input signal.

Claim 4

Dependent Claim 32 words

The companding noise reduction system as defined in claim 2 wherein the single feedforward sidechain further comprises a non-linear low-pass filter which receives as input an output signal from the level detector.

Claim 5

Dependent Claim 38 words

The companding noise reduction system as defined in claim 3 wherein the non-linear low-pass filter further comprises means for decreasing a response time thereof in response to an increase in a rate of change of the input signal.

Claim 6

Dependent Claim 58 words

The companding noise reduction system as defined in claim 4 wherein the single feedforward sidechain further comprises a threshold and ratio circuit which responds in a level-dependent and substantially time independent manner to thereby generate the control signal, wherein the control signal is a function of an instantaneous level of an output signal from the non-linear low-pass filter.

Claim 7

Dependent Claim 51 words

The companding noise reduction system as defined in claim 5 wherein the single feedforward sidechain further comprises a means for reversing a polarity of the control signal, wherein the reversed polarity control signal is transmitted to the second variable gain element to thereby provide an opposite control signal to the decoder.

Claim 8

Dependent Claim 23 words

The companding noise reduction system as defined in claim 5 wherein the control signal is electrically coupled to the first variable gain element.

Claim 9

Dependent Claim 41 words

The companding noise reduction system as defined in claim 5 wherein the threshold and ratio circuit includes means for determining a high and a low threshold, a compansion ratio, and an amount of noise reduction to be achieved by the system.

Claim 10

Dependent Claim 39 words

The companding noise reduction system as defined in claim 1 wherein the transmission path is selected from a group of transmission systems exhibiting limited dynamic range consisting of a graphic equalizer, a parametric equalizer, and an FM broadcast system.

Claim 11

Independent Claim 135 words

A method for noise reduction using a companding system for processing sonic frequencies while minimizing distortion thereof, said method comprising the steps of: (1) compressing the input signal representative of the sonic frequencies to be processed utilizing an encoder, and delivering the compressed signal to a transmission path of limited dynamic range; (2) decompressing the compressed signal received from the transmission path utilizing a decoder to thereby generate the processed sonic frequencies; (3) developing a control signal in a single feedforward sidechain which receives the input signal; (4) controlling gain of a first variable gain element in the encoder utilizing the control signal developed in the single feedforward sidechain; (5) reversing polarity of the control signal; and (6) controlling gain of a second variable gain element in the decoder utilizing the reversed polarity control signal.

Claim 12

Independent Claim 135 words

A method for noise reduction using a companding system for processing sonic frequencies while minimizing distortion thereof, said method comprising the steps of: (1) compressing the input signal representative of the sonic frequencies to be processed utilizing an encoder, and delivering the compressed signal to a transmission path of limited dynamic range; (2) decompressing the compressed signal received from the transmission path utilizing a decoder to thereby generate the processed sonic frequencies; (3) developing a control signal in a single feedforward sidechain which receives the input signal; (4) controlling gain of a first variable gain element in the encoder utilizing the control signal developed in the single feedforward sidechain; (5) reversing polarity of the control signal; and (6) controlling gain of a second variable gain element in the decoder utilizing the reversed polarity control signal.

Claim 13

Dependent Claim 49 words

The method for noise reduction using a companding system as defined in claim 10 wherein the method further comprises the step of detecting an amplitude of the input signal in the single feedforward sidechain, wherein the control signal is developed in response to the amplitude of the input signal.

Claim 14

Dependent Claim 38 words

The method for noise reduction using a companding system as defined in claim 11 wherein the method further comprises the step of processing the control signal utilizing a non-linear low-pass filter after level detection of the input signal.

Claim 15

Dependent Claim 45 words

The method for noise reduction using a companding system as defined in claim 12 wherein the method further comprises the step of decreasing a response time of the non-linear low-pass filter in response to an increase in a rate of change of the input signal.

Claim 16

Dependent Claim 54 words

The method for noise reduction using a companding system as defined in claim 13 wherein the method further comprises the step of generating the control signal utilizing a level-dependent and substantially time independent manner, wherein the control signal is a function of an instantaneous level of an output signal from the non-linear low-pass filter.

Claim 17

Dependent Claim 75 words

The method for noise reduction using a companding system as defined in claim 14 wherein the method further comprises the steps of: (1) determining a high threshold and a low threshold; (2) determining a compansion ratio; (3) determining an amount of noise reduction to be achieved by the system; and (4) setting the high threshold, the low threshold, and the amount of noise reduction to be achieved by the system in the single feedforward sidechain.

Claim 18

Dependent Claim 44 words

The method for noise reduction using a companding system as defined in claim 10 wherein the method further comprises the step of adapting the system to compensate for delays in the transmission path which cause distortion due to phase shift in the transmission path.

Claim 19

Dependent Claim 51 words

The method for noise reduction using a companding system as defined in claim 10 wherein the method further comprises the step of setting noise reduction parameters such that the system is substantially audibly transparent on the sonic signal when a signal level thereof is relatively close to a nominal signal level.

Claim 20

Dependent Claim 45 words

The method for noise reduction using a companding system as defined in claim 10 wherein the method further comprises the step of eliminating a need for component matching in the encoder and the decoder because the control signal is developed from the single feedforward sidechain.

Claim 21

Dependent Claim 44 words

The method for noise reduction using a companding system as defined in claim 10 wherein the method further comprises the step of eliminating errors due to non-linearities associated with a transmission path by utilizing the single feedforward sidechain for the encoder and the decoder.

Claim 22

Dependent Claim 31 words

The method for noise reduction using a companding system as defined in claim 11 wherein the method further comprises the step of utilizing a root mean square (RMS) level detection method.

Claim 23

Dependent Claim 45 words

The method for noise reduction using a companding system as defined in claim 10 wherein the method further comprises the step of minimizing distortion of low frequency signals in the input signal by decreasing audio gain modulation due to a ripple on the control signal.

Claim 24

Dependent Claim 40 words

The method for noise reduction using a companding system as defined in claim 11 wherein the method further comprises the step of providing multiple speeds of operation of the system by utilizing the non-linear low-pass filter as a timing circuit.

Claim 25

Dependent Claim 46 words

The method for noise reduction using a companding system as defined in claim 22 wherein the method further comprises the step of causing the non-linear low-pass filter to react slowly to low frequency signals to thereby avoid distortion associated with level detection of the input signal.

Claim 26

Dependent Claim 53 words

The method for noise reduction using a companding system as defined in claim 23 wherein the method further comprises the step of causing the non-linear low-pass filter to react rapidly to high-level transients to thereby avoid overload distortion associated with attack times that are too slow to reduce the gain of the encoder.

Claim 27

Dependent Claim 42 words

The method for noise reduction using a companding system as defined in claim 24 wherein the method further comprises the step of causing the non-linear low-pass filter to release rapidly when the input signal decays quickly to thereby avoid audible noise modulation.

Claim 28

Dependent Claim 41 words

The method for noise reduction using a companding system as defined in claim 25 wherein the method further comprises the step of reducing dynamic distortion of low frequency input signals without affecting the rapid release time needed to avoid noise modulation.

Claim 29

Dependent Claim 51 words

The method for noise reduction using a companding system as defined in claim 26 wherein the method further comprises the step of setting the low threshold substantially above a noise floor to thereby minimize audibility of the noise modulation because the signal level is sufficiently high to mask the noise modulation.

Claim 30

Dependent Claim 37 words

The method for noise reduction using a companding system as defined in claim 10 wherein the method further comprises the step of eliminating a need for calibration of the system by utilizing the single feedforward sidechain topology.

Claim 31

Dependent Claim 68 words

The method for noise reduction using a companding system as defined in claim 27 wherein the method further comprises the steps of: (1) reducing ripples on a control signal that are generated by the level detector by preventing the non-linear low-pass filter from tracking low frequency input signals; and (2) increasing a cut off frequency of the control signal to thereby react rapidly to a fast input signal.

Claim 32

Dependent Claim 36 words

The method for noise reduction using a companding system as defined in claim 29 wherein the method further comprises the step of preventing distortion of the input signal due to phase shifts in the transmission path.

Claim 33

Dependent Claim 43 words

The method for noise reduction using a companding system as defined in claim 30 wherein the method further comprises the step of utilizing a fast attack, then hold, then rapidly release process in the non-linear low-pass filter to thereby maintain input signal integrity.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2006-04-28	2006-10-28	2007-04-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2010-04-28	2010-10-28	2011-04-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2014-04-28	2014-10-28	2015-04-29	$7700.00	Window Closed / Lapsed

Companding noise reduction system with simultaneous encode and decode

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