The sound propagation parameters for the frequency range 20 to 150 kHz and in terms of wavelength, particle size, acoustic impedance, scattering, diffraction, near field and far field effect, beam spreading have been discussed, for these kinds of media. The design considerations and limitation faced due to the diameter and thickness ratio of a piezoelectric disc, vibrating in thickness mode have been discussed. The considerations for the backing to be provided and front facing of these transducers have been spelled out.

The problem of coupling of transducer of hard front surface with the job under inspection have been discussed for porous and rough surfaces such as of concrete or refractory bricks. Use of grease or a paste as couplants may not be acceptable in many situations as it would soke up in the structure and might be too messy to remove afterwards. Use of dry pressure coupling and transducer design with soft front surface has been described.

The paper also reports on the measurement of acoustic pulse velocity and attenuation through different specially made samples of concrete at spot frequencies of 37, 54 and 150 kHz. A concrete tester (PUNDIT make) along with an oscilloscope has been used for the purpose. Various samples of concrete have been specially made using different mix ratios of cement, sand and aggregate and also different water-cement ratios. Compressive strength of these samples have also been measured. The measured acoustic velocity and attenuation at different frequencies have been analyzed and discussed.