Nonlinear three-port measurements for the determination of high-level excitation effects on the acoustic properties of perforates

The effect of high-level excitation on the acoustic properties of perforates, and formulation of the non-linear part of the impedance is under scientific discussion. Analytical models including the non-linear properties, as well as various experimental studies give varying results for the acoustic impedance. This paper aims to provide detailed results obtained under high-level excitation with different acoustic wave incidence and flow configurations. Contrary to the well-established two-port configuration, here, a three-port measurement technique is used to observe the acoustic impedance of the perforated plate using excitation from the three different directions. Plane wave propagation is considered and physical quantities such as in-hole particle velocity, which is calculated at the perforate sample, are used as the controlling parameters. This paper is an attempt to study the effect of high-level excitation on the acoustic behavior of the perforates with grazing and normal acoustic incidence. Moreover, the non-linear behavior of the perforate determined in presence of an external grazing flow is also discussed.