ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

3pEA8. Measurement of three-dimensional transient motion of surfaces by optical vibrometry.

Joseph Vignola

Harry Simpson

SFA, Landover, MD 20785

Brian H. Houston

Naval Res. Lab., Washington DC 20375-5000

A three-dimensional laser vibrometer for measuring simultaneously the three components of vibration induced displacement on a surface has been constructed and tested [Vignola and Houston, J. Acoust. Soc. Am. 94, 1853(A) (1993) and ASME Winter Meeting, 93-WA/NCA-10 (11/93)]. The device, which is fully submersible, was developed for structural acoustic studies where measurements of full three-dimensional motion can provide insight into the analysis of the sound radiated by a structure. This presentation is principally concerned with the methodology and design of the signal processing schemes for the detection of transient events. Some preliminary data are shown together with an analysis of the sensitivity, noise sources, and other performance characteristics of the system. The data presented has been collected from both a test structure (a piezoelectric cylinder with three accelerometers for comparison) and in a water tank half-filled with filtered sand (mean diameter of 140 (mu)m). In the sand experiment the motion of the water-saturated sand interface was monitored.

A special session on ``Hot Topics on Acoustics'' is presented at each meeting of the Society. A member is chosen from each of three or four of the Society's technical committees or specialty groups to present a tutorial talk on topics of current special interest. The talks are intended to help acousticians become familiar with issues and achievements that are not within their own primary fields of interest.