2. Ultrasonic Wave Velocity and Attenuation Measurements

This chapter describes the ultrasonic wave velocity and attenuation measurements. The measurement of the velocity and attenuation of ultrasonic waves have been the basis of evaluation of a wide variety of physical properties of gases, liquids, and solids. In some cases, the measurements have been made with great precision and accuracy. In other cases, the ready availability of the result was more important than extreme precision. A number of sources of error need to be considered if one is measuring velocity and attenuation. In the first place, error is associated with the measurement of such quantities as time and distance. The measurement of velocity involves measurement, either of the time required for the ultrasonic wave to travel a known distance or of the wavelength and frequency. An insidious source of error in velocity measurements in solids is the effect of the transducer producing the ultrasonic waves and of the bond coupling the transducer to the sample. The investigations of the effect of diffraction on velocity and attenuation measurements for the case of circular, axially concentric transmitting and receiving transducers of the same radius are also presented.