초록 ▼

A circuit for suppressing background noise of a continuous nature while enhancing speech signals, or signals having the transient temporal qualities of speech, includes a signal multiplier which, in the preferred embodiment, receives the composite audio signal along with a control signal present onl

A circuit for suppressing background noise of a continuous nature while enhancing speech signals, or signals having the transient temporal qualities of speech, includes a signal multiplier which, in the preferred embodiment, receives the composite audio signal along with a control signal present only when the speech component of the audio signal is present. The control signal may be derived from an AGC circuit having a slow attack, fast decay characteristic to establish a quiescent output level from the AGC amplifier in the absence of speech. An envelope detector is biased to provide a zero output amplitude in response to the quiescent amplifier output level. Speech components appearing in the amplifier output signal are then envelope-detected and filtered to provide the control signal. Alternatively, the control signal can be derived by envelope-detecting the audio signal, filtering the detected signal to remove its d.c. component representing the continuous noise, and then detecting and filtering again. In still another embodiment, the control signal acts upon a constant amplitude instead of the audio input signal in order to provide a speech-responsive tactile vibration for the deaf.

대표청구항 ▼

An automatic signal enhancement system for processing an audio input signal containing unwanted sustained components and desired transient components and providing a system output signal which is present only when said desired transient components are present in said input signal, said system compri

An automatic signal enhancement system for processing an audio input signal containing unwanted sustained components and desired transient components and providing a system output signal which is present only when said desired transient components are present in said input signal, said system comprising: first means responsive to application of first and second signals thereto for providing said system output signal only when both said first and second signals are present and said first signal exceeds a predetermined amplitude level; second means connected to receive said input signal for providing a control signal at an amplitude above said predetermined amplitude level only when said desired transient components are present in said input signal; means for connecting said control signal to said first means as said first signal; and means for connecting said second signal to said first means; wherein said second signal is said audio input signal; wherein said second means comprises: automatic gain control means responsive to said input signal for providing a further signal at a pre-selected amplitude when only said unwanted sustained component and not said desired transient components are present in said input signal, and for providing said further signal at an amplitude which exceeds said pre-selected amplitude and as a function of the amplitude of said desired transient components when both said unwanted sustained components and desired transient components are present in said input signal; envelope detector means connected to receive said further signal for providing an envelope-detected version of said further signal only when said further signal amplitude exceeds said pre-established amplitude; and filter means connected to receive said detected signal and to provide said control signal; wherein said automatic gain control means comprises: variable gain amplifier means connected to receive said input signal and for providing said further signal; and slow-attack, fast-release gain control means responsive to the further signal for adjusting the gain of said variable gain amplifier means in response to said unwanted sustained components such that said further signal amplitude is maintained at said pre-selected amplitude.