Automatic Volume Control

Automatic Volume Control

General Information and Components

• AWD vehicles also have rear ABS wheel speed sensors (G44, G46).

• On the Basic and Standard amplifiers the digital sound system control module (J525) is integrated with the radio (R).

The ABS control module (J104), the left front ABS wheel speed sensor (G47), the right front ABS wheel speed sensor (G45), the digital sound system control module (J525) and an audio source are part of the speed compensated volume (SCV) function. An interior microphone (R74) is also necessary for the dynamic noise compensation.

Speed Compensated Volume

Depending on the vehicle speed, the volume is increased or decreased. On a FWD vehicle, the ABS control module receives the speed signal from the front ABS wheel speed sensors, evaluates it, and then sends it to the instrument cluster/chassis CAN. On an AWD vehicle, it also receives the signal from the rear ABS wheel speed sensor. The data bus on board diagnostic interface (J533) reads the signal and sends it to the optical MOST-bus.

The signal reaches the digital sound system control module (J525) via the optical bus, which then adapts the volumes based on the value. The volume increases as the vehicle speed increases, or decreases as the vehicle speed decreases. This adaptation is based on how the customer has set the volume, meaning the volume is never lower than the customer's preferred setting.

Dynamic Noise Compensation

Dynamic noise compensation uses the following values in order to control the volume:

• Driving speed

• Blower speed

• Noise from a microphone inside the roof module

• Volume compensation in the MMI

On a FWD vehicle, the ABS control module receives the speed signal from the front ABS wheel speed sensors, evaluates it, and then sends it to the instrument cluster/chassis CAN. On an AWD vehicle, it also receives the signal from the rear ABS wheel speed sensors. The Climatronic control module (J255) sends the information for controlling the fresh air blower (V2) to the comfort CAN. The data bus on board diagnostic interface reads the signal and sends it to the digital sound system control module. Noises are heard by the interior microphone, which is installed inside the roof module and is connected directly to the digital sound system control module. The multimedia control head can then be used to adjust the noise compensation. The front information display control head control module (J523) evaluates the input and then sends it to the digital sound system control module via the optical bus. Using these values, the digital sound system control module then adjusts the volume inside the vehicle. Soft music is made louder as the vehicle speed increases, or loud music will be made softer.











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