Car Cabin Acoustics — Frequency-Domain Analysis

Application ID: 15013

This tutorial shows the analysis of a car cabin in order to study the performance of a sound system in the low to mid frequency range. The cabin is of a typical sedan interior, that is, the inside of a hard-top family car. The model studies the frequency response at the location of a microphone array as well as the modal behavior at low frequencies.

The model is driven by loudspeakers placed in the typical locations of a car interior. A lumped Thiele-Small representation (of the electrical and mechanical domains) is implemented with the Electrical Circuit interface for a generic midwoofer and a generic tweeter. They are coupled to the acoustic domain using the Lumped Speaker Boundary condition. Protective grid covers are also modeled in front of the speakers using the Interior Perforated Plate condition.

Boundary conditions are defined with generic data. The windows, dashboard, and doors are modeled using constant absorption coefficients, while the leather seats are represented with complex-valued surface impedance. The roof trim and the carpet floor are defined using the Porous Layer option in the Impedance boundary condition. The porous materials are modeled with the semi empirical Delany-Bazley-Miki model, using Qunli’s and Miki’s constants to describe respectively foam and fiber materials.

The model relatively easily solves in the frequency domain on a standard desktop computer. The model is solved up to 1 kHz using a direct solver. At higher frequencies the model is solved with an iterative approach that uses the complex shifted Laplacian method (CSL).

This model example illustrates applications of this type that would nominally be built using the following products: