Acoustic properties of perforates under high level multi-tone excitation

Abstract

This paper discusses the effect of high level multi-tone acoustic excitation on the acoustic properties of perforates. It is based on a large experimental study of the nonlinear properties of these types of samples without mean grazing or bias flow. Compared to previously published results the present investigation concentrates on the effect of multiple harmonics. It is known from previous studies that high level acoustic excitation at one frequency will change the acoustic impedance of perforates at other frequencies, thereby changing the boundary condition seen by the acoustic waves. This effect could be used to change the impedance boundary conditions and for instance increase the absorption. It could obviously also pose a problem for the correct modelling of sound transmission through ducts lined with such impedance surfaces. Experimental results are compared to a quasi-stationary model. The effect of the combination of frequency components and phase in the excitation signal is studied.

Scattering to Higher Harmonics for Quarter Wave and Helmholtz Resonators

“…The corresponding nonlinear resistance scales with the amplitude of the velocity in the neck, which itself increases with rising SPL. This can also be seen in experimental 41 and numerical 15 studies.…”

Measurement of acoustic velocity components in a turbulent flow using LDV and high-repetition rate PIV

“…Multi-sine acoustic excitation is of practical interest for acoustic liner investigations since it allows to study the response of a liner to various frequencies through only one measurement campaign, which is thus considerably time-saving. Furthermore, some liners have different impedance responses depending on the spectral content of the excitation (Bodén 2013), which can contain a large number of tones in a context of fan applications. It is thus desirable to provide adequate experimental tools for such studies.…”

Effects of a secondary high amplitude stimulus on the impedance of perforated plates

“…IV A 3. Second, as Bod en 7 showed, the effect of the secondary sound field is to reduce j u p j by increasing the resistance of the perforates. Notably, the reduction of j u p j is dependent on f p .…”

“…4-6. Bod en 7 studied the acoustic properties of perforated plates and orifices under high level multi tone excitation. While mostly focusing on harmonically related stimuli, he found a change of impedance at one frequency when varying the strength of excitation at another frequency.…”