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Accession Number:
AD0623867
Title:
REFRACTION OF SOUND BY JET FLOW OR JET TEMPERATURE,
Corporate Author:
TORONTO UNIV (ONTARIO) INST FOR AEROSPACE STUDIES
Report Date:
1965-05-01
Abstract:
The heart-shaped pattern of subsonic jet noise normally peaks somewhere between 15 degrees and 45 degrees from the axis, depending on conditions, falling off sharply as the axis is approached. Conflicting explanations of this directivity pattern appear in the literature. The present investigation suggests that the deep cleft in the pattern can be attributed mainly to refraction of the sound out of the jet by the velocity and temperature fields. The evidence lies in measurements made of the sound field of a harmonic point source placed within a 34 in. dia. air jet. The source is the orifice of a tube about 116 in. i.d. driven through a conical coupling by a horn-type loudspeaker driver this radiates sound essentially omnidirectionally up to about 15,000 cps. The experiment established the formation of an axial intensity minimum, which appears to be mainly due to refraction. The depth of the refraction valley increases with jet velocity, jet temperature, and sound frequency a depth corresponding to an intensity reduction of the order of 35 dB is attained at M 0.9 for 3000 cps. Author
Pages:
0032
Contract Number:
AF-AFOSR-223-64
Contract Number 2:
AF-AFOSR-672-64
File Size:
0.00MB
