Reduction of inertial end correction of perforated plates due to secondary high amplitude stimuli.

The decrease in reactance of perforated plates at high sound pressure amplitudes is of interest for the design of Helmholtz resonator liners. It is associated with the loss of end correction due to flow separation at the orifices. In practical applications, complex acoustic signals impinge on perforations.

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

High sound pressure levels cause impedance changes in orifices and perforated plates due to vortex shedding and jet formation at the orifices. The effects of an additional high amplitude stimulus, unrelated in terms of frequency and phase, on the impedance of perforated plates received little attention. This work experimentally studies the impedance changes of perforated plates at various primary frequencies when an additional unrelated high-level single tone actuation is applied.

Optical measurement of acoustic pressure amplitudes-at the sensitivity limits of Rayleigh scattering.

Rayleigh scattering is a measurement technique applicable for the determination of density distributions in various technical or natural flows. The current sensitivity limits of the Rayleigh scattering technique were investigated experimentally. It is shown that it is possible to measure density oscillations caused by acoustic pressure oscillations noninvasively and directly.