Ultrasonic Attenuation Measurement and its Applications

The work has been carried out at CSIR-National Physical Laboratory (NPL) on development of method for measurement of absolute attenuation. The paper reports techniques of measurement and the work carried out at NPL referring to the work carried out by earlier workers on attenuation measurement. The beam diffraction correction has either been ignored or taken from a reference graph by earlier workers. Present method developed involves beam diffraction correction and requires no reference values. The method is useful to evaluate attenuation values at different frequencies within 6dB band width of transducer. No need to use different transducers of different frequencies. In the present method a broad band ultrasonic transducer is used in the immersion testing set up. Ultrasonic spectrum analysis technique, using fast Fourier Transform, is used to evaluate various echo amplitudes of the received signals with respect to corresponding frequencies. Measurements were taken on aluminum and steel alloy sample blocks. Technique uses single longitudinal wave normal beam transducer to measure both longitudinal and transverse wave attenuation in materials employing isotropic rod sample at different frequencies.