Sound attenuation of a circular multi-chamber hybrid muffler

Abstract

The sound attenuation of perforated dissipative circular mufflers including a folded resonator and a short expansion chamber is investigated in detail by means of a two-dimensional axisymmetrical analytical approach based on the mode matching technique. The acoustical properties of the bulk reacting porous material and the perforated screen are taken into account to obtain the governing eigenequation for the wave propagation through the absorbent material and central perforated passage. Once the solution of the transverse eigenproblem is computed in all regions, the muffler transmission loss is determined by matching the acoustic pressure and axial velocity across each geometrical discontinuity. In addition, finite element results and experimental measurements are utilized for validation. The acoustic attenuation performance is examined considering the effect of the internal geometry of the muffler, the properties of the sound absorbent material and the porosity of the perforated pipe. Comparison is also provided with hybrid mufflers of earlier studies. It is shown that the acoustic contribution of the folded resonator is reinforced by the presence of the short expansion chamber, providing a good noise attenuation performance in the low and mid frequency range, whereas the dissipative effects associated with the central chamber suppress the high frequency noise, thus leading to a broadband attenuation of sound energy. © 2008 Institute of Noise Control Engineering.

Acoustic attenuation prediction and analysis of perforated hybrid mufflers with non-uniform flow based on frequency domain linearized Navier-Stokes equations

“…1,2 As noise control requirements become increasingly stringent, it is important to design the mufflers with well acoustic attenuation performance. In the past few decades, several analytical and numerical methods [3][4][5][6][7][8] have been employed to predict the transmission losses of perforated hybrid mufflers. The researches only investigated the effect of geometry parameters on acoustic attenuation performance in the absence of flow.…”

Advanced numerical techniques for the acoustic modelling of materials and noise control devices in the exhaust system of internal combustion engines

“…Hybrid silencers can also be included within configurations with dissipation, since they combine the geometric and attenuation characteristics of resonators and dissipative silencers, providing a combination of reactive and dissipative effects. Some works have demonstrated the benefit of combining both types of behaviour in hybrid mufflers, i.e., reactive and dissipative effects for low and high frequencies respectively, which may lead to a broadband attenuation performance including resonant peaks at particular frequencies that can be pre-selected by the designer [59,60,66,116].…”

Modelado analítico-numérico y caracterización experimental de silenciadores de escape híbridos

“…En la referencia [40] se estudia el comportamiento acústico de un silenciador híbrido con resonadores laterales. En las publicaciones [38,39,75] se analiza la atenuación acústica del silenciador híbrido con resonador multianular de entrada y cámara lateral de salida. …”