Sound Attenuation in Solids

Determination of the attenuation of an ultrasonic wave on its way through a medium

The attenuation of an ultrasonic wave on its way through a medium is determined by amplitude measurements using the transmission method on bodies of different lengths. Determining the sound attenuation coefficient at different ultrasonic frequencies provides information about the frequency dependence of the sound attenuation.

Keywords: Sound attenuation in solids, scattering, absorption, reflection, attenuation coefficient, frequency dependence of sound attenuation, transmission measurement

Sound waves lose energy on their way through a medium through various processes such as absorption, scattering or reflection. This loss of energy causes a change in the sound intensity, which decreases with increasing distance. The extent of this attenuation or damping depends on the material. It can be determined by measuring the amplitudes of transmission pulses or reflection pulses in an amplitude scan for different path lengths and can be described by the material-specific attenuation coefficient. In the experiment, these measurements are carried out on acrylic cylinders of different lengths. In order to be able to make statements about the frequency dependence of sound attenuation in acrylic, these measurements are carried out for different sound frequencies.

The graphic above shows the measured values ​​of an example measurement using sound transmission on 3 acrylic test cylinders of different lengths. In the frequency range examined from 1 MHz to 4 MHz, the attenuation coefficients determined were between 2.7 dB/cm and 5.7 dB/cm. It can be seen that the sound attenuation in acrylic increases significantly with increasing frequency. To expand the database to include additional lengths, the cylinders can also be examined using the reflection method.

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