Acoustic Nonlinearity of an Orifice

Abstract

The acoustic nonlinearity of an orifice in a plate has been investigated by measuring simultaneously the oscillatory flow velocity in the orifice and the acoustic-pressure fluctuations producing the flow. The relation between the pressure and velocity amplitudes, which is linear at sufficiently low pressures, is found to approach a square-law relation at large velocity amplitudes. By evaluating the phase relationship between the fundamental harmonic components of pressure and velocity, the acoustic-orifice impedance is determined. In the square-law region of the pressure/velocity relation, the resistive component of the orifice impedance dominates and is proportional to the velocity amplitude. This method of measurement, which is particularly useful at high amplitudes, is supplemented by measurements of sound transmission and frequency response of the orifice plate so that an impedance curve can be constructed over an extended range of amplitudes. An analogous program of measurements has been carried out to study the influence of a superimposed steady flow on the acoustic-orifice impedance. Finally, as an application of the results obtained, the absorption characteristics of resonator absorbers for high-intensity sound are discussed.

Nonlinear asymptotic impedance model for a Helmholtz resonator liner

“…The next order term y 2 is obtained from (22) when it is expanded to Oðε 2 Þ and terms of Oðε 2 Þ are collected …”

“…Ingard and Ising [22] measured simultaneously fluctuating velocity and pressure, using hot wire measurements, followed by the exploitation of their phase relation to obtain the impedance at relatively high amplitudes. The chosen amplitudes were relatively high and in the domain of the Innes and Crighton theoretical model [11].…”

Nonlinear damping and quasi-linear modelling

“…The acoustic flow through a number of different orifices, when excited by sound at different amplitudes, was measured by Ingard & Ising [10]. The flow showed a complicated pattern at very high amplitudes, when the flow becomes supersonic.…”

Non-linear Impedance of a New Sound Absorptive Fibreless Material Title

“…This term is here utilized to describe the non-linear relationship between the acoustic pressure amplitude and the particle velocity taking place when the sound excitation exceeds a certain level. The non-linearities have been object of several studies since the 60s' due to the strong effect on the behavior of the perforated elements [12], [13], [14].…”