Method and system of background noise suppression in an audio circuit particularly for car radios

US4868881A · kind A · utility

Assignee

• Blaupunkt-Werke GmbH · DE

Inventors

• Eberhard Zwicker · Icking, DE
• Klaus Deuter · Freising, DE

Key dates

• Filing date: Sep 1, 1988
• Grant date: Sep 19, 1989
• Expiry date: Sep 1, 2008

Classification

• Technology area (CPC H): Electricity
• CPC primary: H03G3/32
• WIPO field: Basic communication processes
• WIPO sector: Electrical engineering

Abstract

To improve the fidelity of reproduction of automobile radios during conditions of extraneous in the passenger compartment, noise signals are derived, for example from a microphone installed in the engine compartment of the vehicle. The audio program signals are conducted through a multichannel equalizer; the program audio signals and the noise signals are separated into a plurality of frequency bands, for example three bands, the envelope of which are demodulated and the derived demodulation signals are instantaneously compared to then control the transfer characteristics of the respective bands of the equalizer in accordance with the derived comparison between the respective bands of the noise and program signals. Preferably, amplitude, change of transfer amplitude and rate of change is controlled by weighting the comparison signals and the rate of change thereof in relation to the frequency bands and the extent of change of the signals.