In the past, Eberspaecher has installed active exhaust mufflers on several vehicles. In all cases, a substantial reduction of the exhaust noise was achieved. Moreover, not only silencing but also the shaping of different types of sound in these vehicles was implemented. Hence, a variety of sounds are available from one and the same engine. Unlike with conventional passive exhaust systems, the active silencer can be specifically adapted (customized) to the vehicle; to the driving situation; and/or from a request of the driver.
To guarantee that an “anti-noise” system can actually work in practice, various fundamental problems had to be solved. In particular, the ambient conditions prevailling in exhaust systems (enormous heat, moisture and high sound pressure levels) have previously reduced the life span of the loudspeaker that generates the “anti-noise”. Likewise, the rapidly changing engine speeds and load conditions have prevented this technology being applied to the exhaust system in the past. With the development of the ActiveSilence™-System, considerable progress in this domain has recently been made by Eberspaecher.
All these issues will be discussed in the paper with a focus on acoustic results from a chassis dynamometer and road tests achieved on several vehicles. Furthermore, current design trends and possible fields of application will be discussed.