High frequency noise suppression of the automobile exhaust system

The paper presents the decision for the question of the excessive catalytic collector high frequency noise in the automobile engine exhaust system. The high level noise has been observed under the idle state engine condition. In order to understand the causes of the high catalytic collector noise emission the research of its vibroacoustic internals has been performed. An experimental stand for the acoustic and vibration response on broadband dynamic excitation tests has been created. The power of the acoustic noise, emitted by the catalytic collector and vibration distribution of its surface have been defined. It was found that the catalytic collector surface has the low acoustic impedance in the high frequency range. The surface vibration damper design has been developed. A special material, so called metal rubber, has been used to damp the vibration. The main advantage of this material is the temperature tolerance, quite useful for the engine exhaust system unit. The use of the damper has allowed to reduce the structure-born noise of the catalytic collector.

Key words: catalytic collector; structure-born noise; automobile; acoustic power; acoustic impedance; metal rubber