Conference_programme: 19.1 - Duct Acoustics
Lecture: Determination of nonlinear acoustic properties of perforates using band-limited random excitation
Author(s): Sayyad Khodashenas Niloofar, Bodén Hans, Boij Susann
Summary:
Perforates are used for noise control in automotive mufflers and aircraft engines as well as for other vehicles and machines. Their properties and noise reduction are known to depend on the mean flow field and other parameters such as temperature and acoustic excitation level. It is therefore of interest to understand how the properties of perforates varies with the level of acoustic excitation. Methods for studying nonlinear harmonic interaction effects, for perforates, using single tone excitation and Poly-harmonic distortion models or nonlinear scattering matrices has been studied. These techniques typically require measurements with a number of different acoustic loads. It would be more attractive to directly be able to extract the nonlinear acoustic properties from a more limited set of experiments using either random or periodic excitation. Multi input – single output techniques for nonlinear system identification using broadband random excitation has been tried with limited success. One reason is the mixing of the sound pressure signal incident from the acoustic source with the sound pressure transferred to higher frequencies by nonlinear effects at the perforate sample. The present paper is an attempt to combine band-limited broadband excitation with nonlinear scattering matrices describing the nonlinear transfer of energy to higher frequencies. By analyzing acoustic energy transfer at frequencies at least two to three times higher than the high frequency cut-off for the bandlimited broadband random signal it may be possible to extract information to estimate the parameters of the non-linear scattering matrix.
Corresponding author
Name: Prof Hans Bodén
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Country: Sweden
