Audio signal processor

Claim 2

An electrical signal processor comprising: a. a system input means for receiving variable value electrical signals; b. detector means for detecting the absence of an electrical signal having a predetermined value at said system input; c. attenuator means having an attenuator input means connected to said system input and being operable by said detector means for variably attenuating the electrical signal appearing at said system input and forming said attenuated signal on an attenuator output means when said detector means detects the absence of an electrical signal having said predetermined value and for transmitting said signal appearing at said system input to said attenuator output means without attenuation when said detector means detects the presence of an electrical signal in excess of said predetermined value; and d. automatic signal value control means including an automatic volume control circuit connected to said attenuator output means for automatically forming a fixed value output signal irrespective of value variations within a predetermined range in said signal appearing on said attenuator output means, said attenuator means being operable to attenuate at a rate equal to the gain rate of said automatic volume control circuit for preventing noise surges in the intervals when said system input signal value is below said predetermined value, said detector means including an electrical switch means operable in response to the presence of voice sounds for delaying the attenuation function of said variable attenuator means for a predetermined period of time following detection of the absence of said predetermined value signal at said system input and said switch means being operable for preventing the suspension of attenuation at said system input for a predetermined period of time to prevent sounds triggering from impulse noise; and detector adjustment means for adjusting the signal threshold level required for operation of said switch means to increase its noise immunity.

Claim 3

The signal processor as defined in claim 1 wherein: a. said detector means includes means for detecting the presence at said system input of electrical audio signals above a predetermined amplitude corresponding to speech input and the absence of signals above such predetermined amplitude corresponding to no-speech input; b. said switch means includes means for forming a first control output signal when speech level amplitude signals appear at said system input and for forming a second control output signal when speech level amplitude signals are absent from said system input; c. said first and second control output signals being conveyed by conductor means to said variable attenuator means; d. means operable by said first and second control output signals included in said attenuator means to suspend the attenuation function of said variable attenuator means when said first control output signal is formed and means for activating said variable attenuator function when said second control output signal is formed; e. said automatic volume control means maintains a substantially constant amplitude output signal over a fixed range of input amplitudes; f. said attenuator means includes a maximum attenuation value which is equal to the maximum gain value of said automatic volume control means; g. said attenuator means reduces attenuation at the same rate as said automatic volume control means increases gain following a period of no-speech input to said system input to cancel initial system gain following suspension of said variable attenuation function; h. said switch means being operable for preventing the formation of said second control output signal for a predetermined period of time following the loss of speech level amplitude signals at said system input to prevent signal attenuation by said variable attenuator during short duration pauses in speech level system input; and i. said switch means being operable for preventing formation of said first control output signal for a predetermined time following speech level amplitude signal detection for preventing suspension of signal attenuation by said attenuator means following short duration, impulse noise input to said system input.

Claim 4

The signal processor as defined in claim 1 wherein said attenuator means includes: means for adjusting the attenuation rate of said attenuator means; and means for adjusting the maximum value of attenuation introduced by said attenuator means.

Claim 5

The signal processor as defined in claim 1 further including: a. a microphone for transducing sound energy to an electrical signal output; and b. a preamplifier connected to said microphone for amplifying the electrical signal output of said microphone and supplying said amplified signal to said system input.