Influence of gas bubbles on sound transmission of sonar dome

An estimation of air bubbles influence on sonar dome insertion loss is an important problem of acoustic measurements in hydroacoustic tank. Air bubbles cover sonar dome surface and result to unpredictable strong effect on accuracy of measurement results. It takes some time before measurements after immersion of sonar dome and acoustical antenna in water to reduce number of bubbles. Long idle time leads to increasing of measurements cost. Influence of gas bubbles on sound transmission via sonar dome is considered in the paper. Bubbles affect sound transmission in two ways: by changing of surface impedance and by shielding of the active area of the dome. The problem is solved by means of parameters definition of equivalent circuit of dome-bubbles system. Calculations of the sound transmission are carried out for different statistical laws of bubbles radiuses distribution and different concentration of bubbles. It is shown that shielding effect of bubbles is dominating for sound transmission. Obtained results are also useful for the solution of an inverse task: for evaluation of concentration and bubbles radiuses distribution on the base of measured sound transmission coefficient through the sonar dome with and without bubbles.