Sound Actuator

A sound actuator (also known as soundaktor, or in English-speaking regions as sound actuator) is a component of the Active Sound System developed and produced by Eberspächer. Its function is to simulate engine sounds in a vehicle.

A sound actuator is essentially a special speaker that receives sound data from a dedicated sound module.

Soundaktor Soundaktuator

The sound actuator is mounted at the end of the exhaust pipe and connected to the exhaust system via a pipe.

Sound actuator with exhaust system

Sound Actuator and Sound Module – How the Active Sound System Works

The sound module calculates which sound frequencies need to be enhanced using algorithms and engine control unit data, such as RPM, to improve the vehicle's sound.

The generated signal is amplified and sent to the sound actuator. The built-in speaker then emits the artificial vehicle sound.

Structure of Sound Actuators

The images below show the internal structure of a sound actuator:

Sound actuator side view

Sound actuator internal side view

Sound actuator interior

Sound actuator bottom view

Sound actuator exhaust integration

(Images copyright Eberspächer, taken from patent documents)

Origin of the Sound Actuator

The original purpose of the sound actuator was to reduce or cancel unwanted sounds. Eberspächer developed and patented it as an active muffler.

Unlike today's use, it was designed to counteract the vehicle's sound rather than add new sound.

The principle is anti-noise. Using a built-in speaker, the actuator generates a sound wave that cancels out engine noise via phase shifting. This is meant to reduce sound emissions in the exhaust system.

This technology is known as Active Noise Cancellation (ANC). However, today’s sound actuator is primarily used to *add* sound.

This change came when VW began equipping new models, such as the Audi lineup and the Golf 7, with a built-in sound actuator starting in 2011.

The goal was to give modern, quiet cars a more exciting sound—something lost due to improved insulation and smaller, more efficient engines.

Active Sound technology became a success, and other manufacturers followed suit. Besides VW and Audi, brands like Porsche, BMW, and Skoda also use sound actuators in various models.