Reduction of peak jet noise using jet refraction

Philip John Morris, W. Richarz, H. S. Ribner

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The directivity pattern of sound generated by a subsonic jet exhibits a peak at angles between 15 and 45 degrees to the jet axis, decreasing to a minimum on the jet axis. Theoretical and experimental investigations have previously demonstrated that this minimum is due to refraction of sound by the jet flow. The present experimental study considers the effect of the introduction of a second jet of smaller exit area near to the main jet. It is shown that the small jet imposes its own heart-shaped directivity pattern on that of the first jet. Alteration of the angle between the two jets leads to a reduction in the peak sound level. Directivity patterns for unfiltered and filtered measurements are presented for changes in the jet velocities and temperature ratios. Calculations of the perceived noise level radiated by one and two jets of larger scale are made. The change in ground area effected by various noise levels are given for an aircraft taking-off using a number of alignments of auxiliary engines to alter the pattern of radiated sound.

Original languageEnglish (US)
Pages (from-to)443-455
Number of pages13
JournalJournal of Sound and Vibration
Volume29
Issue number4
DOIs
StatePublished - Aug 22 1973

Fingerprint

jet aircraft noise
Refraction
Acoustic noise
refraction
directivity
Acoustic waves
acoustics
temperature ratio
jet flow
aircraft
engines
alignment
Aircraft

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Acoustics and Ultrasonics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Morris, Philip John ; Richarz, W. ; Ribner, H. S. / Reduction of peak jet noise using jet refraction. In: Journal of Sound and Vibration. 1973 ; Vol. 29, No. 4. pp. 443-455.
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Reduction of peak jet noise using jet refraction. / Morris, Philip John; Richarz, W.; Ribner, H. S.

In: Journal of Sound and Vibration, Vol. 29, No. 4, 22.08.1973, p. 443-455.

Research output: Contribution to journalArticle

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AB - The directivity pattern of sound generated by a subsonic jet exhibits a peak at angles between 15 and 45 degrees to the jet axis, decreasing to a minimum on the jet axis. Theoretical and experimental investigations have previously demonstrated that this minimum is due to refraction of sound by the jet flow. The present experimental study considers the effect of the introduction of a second jet of smaller exit area near to the main jet. It is shown that the small jet imposes its own heart-shaped directivity pattern on that of the first jet. Alteration of the angle between the two jets leads to a reduction in the peak sound level. Directivity patterns for unfiltered and filtered measurements are presented for changes in the jet velocities and temperature ratios. Calculations of the perceived noise level radiated by one and two jets of larger scale are made. The change in ground area effected by various noise levels are given for an aircraft taking-off using a number of alignments of auxiliary engines to alter the pattern of radiated sound.

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