US 4,641,361 A · Multi-band automatic gain control apparatus

Abstract

A multiple band automatic gain control circuit having a band splitter which is responsive to an input audio signal for separating the audio signal into plural components of different frequencies. Plural gain adjustment circuits each control the gain of an associated one of the components, wherein each of the gain adjustment circuits includes a voltage controlled amplifier, and feed forward control elements for controlling the voltage controlled amplifier as a function of the amplitude of the associated component. A signal combiner combines the gain adjusted components to thereby form a gain adjusted audio signal. A limiter circuit prevents the combined signal from exceeding predetermined amplitude constraints by simultaneously reducing the gain of all of the variable gain circuits whenever the combined signals exceed the predetermined constraints.

Claims20

Dependent claims

Audio signal processing apparatus comprising:

band splitter means responsive to an input audio signal for separating the audio signal into plural frequency components;
plural gain adjustment means for each controlling the gain of an associated one of said components, each said gain adjustment means including variable gain means for gain adjusting the corresponding component, and feed forward control means for controlling the gain of said variable gain means as a function of the magnitude of the associated said component;
signal combining means for combining the gain adjusted components provided by said plural gain adjustment means to thereby form a gain adjusted audio signal;
and
limiter means for preventing the combined signal from exceeding predetermined amplitude constraints, said limiter means including means for simultaneously reducing the gains of all said variable gain means whenever said gain adjusted audio signal exceeds said constraints.

2 more elements

Audio signal processing apparatus comprising:

band splitter means responsive to an input audio signal for separating it into plural frequency components;
plural gain adjustment means for each controlling the gain of an associated one of said components, each said gain adjustment means including variable gain means for gain adjusting the corresponding component, and feed forward control means for controlling the gain of said variable gain means as a function of the magnitude of the associated said component;
and
signal combining means for combining the gain adjusted components provided by said plural gain adjustment means to thereby form a gain adjusted audio signal,
wherein each said feed forward control means includes attack/release means for generating a first signal which varies dynamically as a short term function of the corresponding said component, gain gate circuit means for generating a second signal which varies as a long term function of said component, and means for controlling the corresponding said variable gain means as a function of both said first and second signals.

2 more elements

Dependencies are inferred from the claim text.

Multi-band automatic gain control apparatus

Life of this patent

Multi-band automatic gain control apparatus

Life of this patent

Abstract

Claims20