Acoustic property testing of materials, attenuation and speed of sound

Acoustic property testing of materials, attenuation and speed of sound

NPL can measure the attenuation and speed of sound in liquids and solids, typically over the frequency range 1 to 20 MHz. Solid or solid-like samples are normally required in the form of right-circular cylinders of minimum diameter 50 mm and thickness 5 mm or greater.

For liquid samples special liquid reference cells can be used for measurements which are made using a through transmission immersion technique by interposing the sample between a broadband hydrophone and transducer.

For measurements where the temperature variation of the acoustic properties of materials is required, this can be carried out over the temperature range 5 °C to 50 °C.

For the most accurate measurement of speed-of-sound in liquids, an ultrasound pulse-echo facility exists which monitors the change in arrival time of a reflected pulse when the distance between a transducer and polished reflector is accurately altered.

The technique is appropriate for application to relatively small liquid volumes and measurements can achieve an uncertainty as low as ±0.01%. Again, the temperature dependence of the speed of sound in liquids can be measured over the range 5 °C to 50 °C although with slightly degraded uncertainties.