Accession Number : AD0706844

Title :   INVESTIGATION OF ANOMALOUS BEHAVIOR OF SOUND ABSORPTION BY MOLECULAR RELAXATION.

Descriptive Note : Technical memo.,

Corporate Author : WYLE LABS INC HUNTSVILLE ALA RESEARCH STAFF

Personal Author(s) : Evans,L. B. ; Sutherland,L. C.

Report Date : MAY 1970

Pagination or Media Count : 34

Abstract : Experimental measurements of the absorption of sound in still air exhibit a distinct deviation from the theoretical predictions based on known classical and molecular relaxation absorption losses. Investigation of published laboratory data has verified that Kneser's theory for molecular relaxation accurately describes the absorption loss near and above the relaxation frequency. At frequencies less than about 0.1 of the relaxation frequency, a different mechanisms becomes predominant and results in an absorption loss component which varies directly with the frequency and is essentially independent of humidity. The objective of the effort in this contract is to carry out a detailed experimental and analytical investigation of this anomaly to allow numerical calculations to be made of air absorption for a variety of atmospheric conditions in still air. (Author)

Descriptors :   (*AIR, *ACOUSTIC PROPERTIES), ABSORPTION, HUMIDITY, RELAXATION TIME, ANOMALIES, WATER VAPOR, NITROGEN, MOLECULAR ENERGY LEVELS

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE