Acoustic reflection from elastic spheres. I. Steady-state signals

Abstract

Measurements are made of the acoustic reflected pressure from aluminum and tungsten-carbide spheres for ka values between 5 and 20. Only the farfield monostatic case is considered. Experimental values are compared to a harmonic-wave solution. Excellent agreement is observed when the wave speeds in the sphere material are adjusted by an amount smaller than the known uncertainty in the wave-speed values in the solids. The position of rapid changes in the reflection solution with ka is found to be very sensitive to shear-wave speed and insensitive to longitudinal-wave speed. The sensitivity to ambient temperature of the position of a selected minimum in the reflection solution is examined computationally for an aluminum sphere. A shift in the value of ka at which a minimum is calculated is also observed experimentally. Long pulses are used to approximate steady-state conditions and agreement with the steady-state theory shows that this approximation is adequate.