Deformation of sound pressure pulse and that of particle velocity pulse with diffraction.

Abstract

When ultrasonic pulse travels in homogeneous material, it shows deformation by diffraction. An important approach to analyze this effect is to compute retarded potential of ultrasonic field together with Fourier's analysis. Deformation of sound pressure pulse with diffraction and that of axial component of particle velocity pulse with it are dealt with a numerical method by Fourier's analysis. They are compared each other in the case that a pulse is transmitted from a circular flat transmitter into isotropic and non-absorptive medium. Analyzed transmitting pulses are assumed to have several envelopes of ramp followed by exponential decrease with sinusoidal carrier wave. Waveforms of receiving pulses through a few transmission systems with a circular flat transducer and a point one and those with a pair of coaxial circular flat ones are derived. Ratio of peak value of receiving pulse to that of transmitting one is obtained with a computing precision of 0.1%. It corresponds to apparent attenuation of pulsed ultrasonic wave by beam divergence when a pair of circular flat transducers are considered.