Rain parameter estimation using impact generated low-frequency acoustic signals

Abstract

The role of rain generated acoustic signals in the frequency range 500 Hz–100 kHz to estimate the rain parameters is well known [Medwin et al., J. Acoust. Soc. Am. 92, 1613–1623 (1992)]. A study of utilizing the low-frequency component below 500 Hz, present in the rain generated acoustic noise, for estimation of rain parameters is performed in this paper. Raindrops falling from various heights are simulated using a drop generator. Gravity waves are produced in the water surface due to the drop impact and this causes a sinusoidal low-frequency damped pressure wave in water. This low-frequency signal is captured using a sensor assembly and analyzed. It is observed that this component is fairly constant in its frequency while amplitude is found to vary in accordance with the drop size as well as the velocity. Drop-size and its kinetic energy are determined and compared with those obtained from theoretical computations and by direct measurements. The results show that this new technique of analysis of rain generated acoustic signals yields rain parameters with good degree of accuracy. This method has the advantage of savings in computation time and simplicity of design.