Experimental Investigation of Surface Wave Phenomena by Sound Pulse Techniques
Mary L. Harbold, Bruce N. Steinberg · The Journal of the Acoustical Society of America · 1967
Experimental pulse techniques have been developed to verify directly the existence of creeping or circumferential waves that arise from theoretical diffraction theory as developed mathematically by the Watson transformation acoustic step pulses and sine-burst pulses of varying duration and frequency, produced by a transducer using modulation of an ion cloud, are scattered from a rigid sphere in air. The detection transducers, positioned near to and imbedded in the surface of the scatterer, yield measurements of both the amplitude attenuation and velocity of the creeping wave recorded by high-speed, multitrace oscilloscope techniques in conjunction with sample/hold digital data storage. Electronic gating circuits switch the transducers on and off individually or in coincidence as the pulse front advance. The transducers are synchronized in tandem with the pretrigger, trigger, and delayed trigger circuitry of six independent oscilloscope traces. [This work was supported by the U. S. Navy, Office of Naval Research.]