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In many applications, broad-band ultrasonic transducers capable of producing short video pulses are required. Previously, plane-wave analysis with equivalent circuits has proven successful in predicting pulse shape in the time and frequency domains. The present approach is to recognize that piston sources radiate nonplanar waves, and that the frequency spectrum of a broad-band piston source can be measured experimentally. With the spectrum as a weighing function for the field profiles of a monofrequency piston source, a superposition is performed to find the pressure and phase profiles in the radiation field of a broad-band transducer. Experimental measurements are presented that take advantage of the broad-band pulse technique combined with spectrum analysis. These include thickness gauging of thin materials and interface layers, and relative viscosity measurements.

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Ultrasonic velocity and attenuation measurements have been made by traveling-wave methods on several refractory metals and their alloys. Broad-band pulses centered around 120 kHz were used for extensional waves (and some torsional waves) in wire specimens. Elastic moduli calculated from the velocities decrease with increasing temperature; the slope increases in magnitude at about half the absolute melting point. At the same point, the attenuation begins to increase rapidly and peaks 300--600·C above the breakpoint. These effects are ascribed to absorption in grain boundaries. The transit time versus temperature in rhenium wire has been calibrated for the use of rhenium as an ultrasonic thermometer sensor. Ultrasonic thermometry above 2000·C is an application of the present measurements.

Ultrasonic transducers for low-intensity i n d u s t r i a l and medical a p p l i c a t i o n s can be analyzed and evaluated i n f i v e interconnected "domains", namely time, space, frequency, s u r f a c e m t i o n , and theory. f o r t h e frequency domain. a s p e c t s of t h e a c t i v i t y o f i t s s u r f a c e can be measured by a C-scan t a r g e t e d on a r i g i d sphere i n water. methods can be portrayed by holography or with an SEM. by transmission l i n e theory where each l a y e r of t h e transducer s t r u c t u r e is t r e a t e d as a s e c t i o n o f transmission l i n e .