On solid noise solutions in waveguides

Restrictions on unwanted sound, noise are more and more stringent. In many applications, airborne noise travels from the source to the receiver via transmission path consisting of waveguides. Typical applications include ventilation ducts and internal combustion engine intake and exhaust systems, for example. Usually in these applications, resistive silencers are designed for noise attenuation in selected frequency range. Wool and fiber based resistive materials cause back-pressure and have limited lifetime. Major problem with these materials is development of brittleness which leads to decrease in attenuation performance and when broke down in pieces, might cause major failures in connected devices. In addition, microfibers contaminate air. In this paper, wool and fiber less noise control techniques are discussed. In addition, acoustic properties of panel resonators and micro perforated panel silencers are simulated with different geometries.