Accession Number : AD0647356

Title :   SYSTEMATIC ERRORS IN ULTRASONIC PROPAGATION PARAMETER MEASUREMENTS. PART III. SOUND SPEED BY ITERATIVE REFLECT ON-INTERFEROMETRY.

Descriptive Note : Interim rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON D C

Personal Author(s) : Del Grosso,V. A.

Report Date : 09 AUG 1966

Pagination or Media Count : 252

Abstract : This report shows that, although the free-field diffraction and guided mode dispersion errors detailed in Parts 1 and 2 of this series do carry over to the case of iterative reflection (accomplished by adding a termination to the liquid cylinder), the errors for a given geometrical configuration are smaller for interferometry than for nonterminated or pulsing situations. Indeed, the approach with improved parameters is toward plane wave results for interferometry rather than toward free-field results as is the case for pulsing. Other advantages accruing to interferometry are (a) the use of differential instead of total, acoustic paths, (b) the simplified determination of these paths by the use of parallel source and reflector, (c) the simple measurement of frequency rather than small time intervals, and (d) the suitability of the method for determinations of chemical concentration (salinity) and pressure coefficients, as well as the temperature coefficient. This report includes many impedance circle plots as well as the more usual reaction plots for ultrasonic interferometers with walls that are either infinitely flexible, absolutely rigid, liquid, or elastic. Various parameters including tube size, source-to-reflector separation, frequency, and attenuation coefficients are included along with several imposed characteristics. The plot readings, and apparent sound speeds calculated from them, are tabulated. Errors may be as large as a few percent or as small as 6 parts per million (0.01 m/s). (Author)

Descriptors :   (*SOUND, *PROPAGATION), VELOCITY, ACOUSTIC SIGNALS, ATTENUATION, ACOUSTICS, INTERFEROMETERS, REFLECTION, BOUNDARY LAYER, INTERFACES

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE