Gated photon correlation spectroscopy for acoustical particle velocity measurements in free-field conditions.

The measurement of acoustic pressure at a point in space using optical methods has been the subject of extensive research in airborne acoustics over the last four decades. The main driver is to reliably establish the acoustic pascal, thus allowing the calibration of microphones with standard and non-standard dimensions to be realized in an absolute and direct manner. However, the research work so far has mostly been limited to standing wave tubes.

Characterization of solid complex multiphase systems based on oscillatory photon correlation spectroscopy.

The particle loading and dispersion profiles are two significant properties directly affecting the engineering properties and performance characteristics of polymer nanocomposites. Current measurement techniques are often destructive, require special sample preparation, are limited to small, unrepresentative sample size, and/or cannot discriminate between the two aforementioned parameters. This Letter demonstrates the application of photon correlation spectroscopy on mechanically oscillated solids; experimental results show that this technique can discriminate between different grades of such materials.

Absolute calibration of hydrophones immersed in sandy sediment.

An absolute calibration method has been developed based on the method of three-transducer spherical-wave reciprocity for the calibration of hydrophones when immersed in sandy sediment. The method enables the determination of the magnitude of the free-field voltage receive sensitivity of the hydrophone. Adoption of a co-linear configuration allows the acoustic attenuation within the sediment to be eliminated from the sensitivity calculation.