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2 Hydroacoustics

2 1997

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Ultrasonic transmission experiments on porous materials

Kelders L., Lauriks W., Thoen J.

Hydroacoustics

1997

Vol. 1

307--310

The experiments are based on the detection of air-borne slow compressional waves after transmission through absorbent porous materials. The measurement of the attenuation and the velocity of the slow wave at ultrasonic frequencies enables us to determine some important material parameters which are needed for the prediction of the acoustic performance (in the audible range) of the samples. In addition, an XY positioning system is useful for probing the samples at different positions. The difference in velocity and attenuation as a function of the measuring point on the sample gives information on the homogeneity of the material. This leads to non-destructive testing and to a study of the difference in material properties within one sample.

Laser generation and detection of interface waves for the acoustic spectroscopy of liquids

Desmet C., Gusev V., Lauriks W., Thoen J.

Hydroacoustics

1997

Vol. 1

295--298

The pulsed heating of the interface between a solid and a liquid leads to the excitation of acoustic interface waves. These interface waves are detected at a variable distance from the generation region by means of a beam deflection setup. By evaluating the amplitude and phase spectra (using a Fast Fourier transform) of two wave pulses at two different source-receiver distances, the velocity of propagation and the attenuation of the interface waves are measured as a function of frequency (bandwidth of 50 MHz). By fitting these experimentally determined results to theory it is possible to determine the acoustic properties of the liquid as a function of frequency.