The influence of acoustic nonlinearity on absorption properties of Helmholtz resonators. Part II. Experiment

An experimental study of an effect of the acoustic
nonlinearity on absorption properties of Helmholtz resonators is presented in
this work. By use of the classical standing wave method the changes in the
absorption coefficient and the resonators impedance were investigated at
moderate and high amplitudes of incident wave. As a result of nonlinearity a
high absorption at resonance frequencies was observed and then a decrease in
this absorption with increasing amplitude. Measurements of the total loss
resistance of resonators have indicated that a change in the resistance at high
amplitudes depends strongly on resonator orifice area, the smaller area - the
higher increase in the resistance. The experimental results have also shown a
growth in resonators reactance which causes an increase in resonance frequency.
Quite a good agreement between experimental data and the theory presented in
Part I was found.