A Two-Hydrophone Technique for Measuring the Complex Reflectivity of Materials in Water-Filled Tubes
Abstract
A two-microphone technique has been developed by Blaser, Chung, Seybert, and others for measuring the complex reflection factor, and through it the complex acoustic impedance, of a material surface in tubes containing air. The procedure consists of simultaneously sampling the stationary acoustic field at two locations in front of an ensonified sample. This thesis describes an extension of this technique to measure the same characteristics in water-filled tubes. However, because of the close acoustic coupling between the water and the tube walls, a number of modifications were needed in order to implement the technique. These included the development, after several attempts, of a two- hydrophone system that did not perturb the acoustic field and yet was isolated form any structure-borne noise, and the development of more elaborate signal processing procedures in which pulses of sound rather than a continuous sound field were projected to ensonify the tube. Subsequent measurements indicated that the technique could be performed in water using both pulsed and continuous sound fields. A comparison of measured values of the complex reflection factor of three different simple terminations (air, steel, rubber), using the two- hydrophone technique and the more conventional standing wave ratio procedure, indicates good agreement over the frequency range of interest, with the added advantage of a considerable savings in time and experimental effort.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 27, 1982
- Accession Number
- ADA130613
Entities
People
- Scott Sutherland Corbett Iii
Organizations
- Pennsylvania State University