05204971 is referenced by 39 patents and cites 4 patents.

A sound system for a vehicle detects the amount of noise, such as road noise, and automatically controls the audio volume in accordance with the noise amount. There are provided a plurality of tables, in which the relationships among the present volume, the noise amount and the volume increase amount of the audio signal are stored. Once one of the plurality of tables is selected by using a table selection key according to the type of the vehicle or the sound system, the volume is automatically controlled based on the characteristic of the selected table.

Title
Vehicle sound system
Application Number
7/766615
Publication Number
5204971
Application Date
September 26, 1991
Publication Date
April 20, 1993
Inventor
Yoshikatsu Watanabe
Iwaki
JP
Masahiro Takahashi
Iwaki
JP
Agent
Norman R Klivans
Guy W Shoup
Assignee
Alpine Electronics
JP
IPC
H04B 1/00
H04B 1/18
View Original Source