Abstract :
An audio system in an automobile suffers from its ambient noise. If a driver, in a car on express way or gravel road, is listening to a car radio or a car stereo, the sound of them will probably be masked by the vehicle-noise. Therefore, it is frequently required to adjust the loudness of sound. It is, however, dangerous for the driver to adjust the loudness during the car in motion. Moreover, when ambient noise level is decreased, it is annoying to hear too loud sound which was previously adjusted. The automatic loudness adjusting circuits for automotive audio system have been developed for the purpose of improvement of aforementioned inconvenience.
