Research on two methods of acoustic isolation

Abstract

In sound fields, the incident wave and the reflected wave are superimposed together; but sometimes we need to isolate the sound waves. In this paper, we present two methods of isolating the incident wave and the reflected wave in the sound fields, the two methods are: the double-pressure sensor method; and, the pressure-velocity sensor method. The double-pressure sensor method involves obtaining the sound pressure from two different locations, and solving the sound pressure and particle velocity at the midpoint of the double-pressure sensor by the accumulative method. The pressure-velocity sensor method involves accessing the sound pressure and velocity at a certain position. And we give the reason for errors of the double-pressure sensor method. For the double-pressure sensor method, many factors could affect the separation results of the incident wave and the reflected wave because of the approximate deduction in the accumulative separation process. Factors that may have affected the result include: the primary sound source frequency; the sampling rate; the distance between the double sensors; the distance between the midpoint of the two sensors and the reflection surface; and, the reflection coefficient. If we can obtain the sound pressure and particle velocity at the same point in the sound field, and bypassing the approximate deduction, the change in these parameters would not have any impact on the separation results. Therefore, we use the pressure-velocity sensor method in order to isolate the incident wave and the reflected wave. We carried out the experiment in a standing wave tube by the pressure-velocity sensor method, and processed the experimental data obtained in the standing wave tube. And we analyze the effect of isolating the incident sound wave and the reflected sound wave. We find that the pressure-velocity sensor method is a good method.