Vibroacoustic Simulation

10 Application of Random systems

The random description of vibroacoustic systems is well suited for large and complex systems with high Helmhotz number. Thus, large technical systems are excellent applications for SEA. These are buildings providing large cavities and walls, ships, trains, and aircraft. Even the acoustics of cars can be calculated by SEA when we keep in mind that the statistical conditions are not perfectly met, and one can accept a certain uncertainty.

However, this chapter explains the principle procedures to perform a SEA simulation, the way of subsystem description, and the determination of the coupling loss factor on realistic examples. We try to find a compromise between presenting realistic examples and being not too sophisticated.

10.1 Frequency Bands for SEA Simulation

In Chapter 9 we used narrow band spectra, because we dealt with deterministic excitations and responses. In general the nature of the excitation signal determines the result, and this can be an amplitude, an rms-value, or a spectral density. This is also true for SEA systems. Here, the input is power, and the output is energy.

Due to the statistic nature of the reverberant fields, SEA simulation uses third-octave bands, because frequency averaging can further improve the statistics. The perception of human hearing is linked to octaves. A doubling of the frequency is called an increase of one octave. According to this and in order to facilitate the comparison of test and simulation results, ...