Overview
This document contains the following information:
Engine sound generation
Engine noise reduction
General
The engine sound function fulfills one of the following two functions, depending on the equipment installed:
Simulating engine and exhaust sounds in the vehicle interior
Reducing engine noises in the vehicle interior
Function requirement
Engine running.
Engine sound generation
The following signals define the current driving condition:
Drive program/engaged drive range
Vehicle speed
Engine torque
Engine speed
The sound system amplifier control unit or the multimedia system control generates a simulated engine sound on the basis of the driving condition.
The speaker system outputs the simulated engine sound even when no audio source is active. If audio output is active, the simulated engine sound is expanded by the current audio source.
Engine noise reduction
For the engine noise reduction function, additional microphones are integrated in the vehicle to measure the engine noises in the vehicle interior. Two microphones are located in the housings of the hands-free system microphones. Two further microphones are located in the area of the grab handles in the rear passenger compartment.
Engine noise reduction analyzes the signals of the microphones. Engine noise reduction calculates counter-signals (inverted signals) based on these signals in order to reduce audible, low-frequency engine noise in the vehicle interior at cylinder shutoff. Depending on the model, engine noise reduction is controlled by the sound system amplifier control unit.
The speaker system outputs the counter-signals even when no audio source is active. If audio output is active, the counter-signals expand the current audio source. The counter-signals overlay the engine noises in the vehicle interior and eliminate them almost entirely.