A 3D Linear Acoustic Network Representation of Mufflers with Perforated Elements and Sound Absorptive Material

Paper #:
  • 2017-01-1789

  • 2017-06-05
The acoustics of automotive intake and exhaust systems is typically modeled using linear acoustics or gas-dynamics simulation. These approaches are preferred during basic sound design in the early development stages due to their computational efficiency compared to complex 3D CFD and FEM solutions. The components of the intake and exhaust systems are typically modelled as frequency-domain 1D linear acoustic transfer matrices or equivalent 0D/1D elements in time-domain nonlinear gas-dynamics and these methods were previously limited to the plane-wave region. In order to improve the accuracy of the gas-dynamic simulation approach, the geometrical description of a muffler was discretized into a 3D acoustic network of 0D cells in order to capture 3D acoustical effects and extend the frequency range to cover higher order modes. This 3D acoustic network is composed of cells orthogonally connected to the adjacent cells and each cell element defines the characteristic dimension at that particular point of the geometry. This geometrical discretization approach was recently applied to a 3D linear acoustic network formulation where an equivalent acoustic multi-port representation of each cell element was used. The 3D linear acoustic network is then reduced to an equivalent acoustic two-port transfer matrix which describes the acoustic characteristic of the muffler. As the typical automotive muffler includes perforated elements and sound absorptive material, this paper demonstrates the extension of the proposed 3D linear acoustic network description of a muffler including the aforementioned elements. The proposed method was then validated against experimental results from muffler systems with perforated elements and sound absorptive material.
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