Experimental and Analytical Studies of Shielding Concepts for Point Sources and Jet Noise.

Abstract

This analytical and experimental study explores concepts for jet noise shielding. Model experiments centre on solid planar shields, simulating engine-over-wing installations and 'sugar scoop' shields. Tradeoff on effective shielding length is set by interference 'edge noise' as the shield trailing edge approaches the spreading jet. Edge noise is minized by (1) hyperbolic cutouts which trim off the portions of most intense interference between the jet flow and the barrier and (2) hybrid shields - a thermal refractive extension (a flame); for (2) the tradeoff is combustion noise. In general, shielding attenuation increases steadily with frequency following low frequency enhancement by edge noise. Although broadband attenuation is typically only several decibels, the reduction of the subjectively weighted perceived noise levels is higher. In addition, calculated ground contours of peak PN dB (perceived noise level) show a substantial contraction due to shielding: this reaches 66% for one of the 'sugar scoop' shields for the 90 PN dB contour.

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Document Details

Document Type
Technical Report
Publication Date
May 01, 1983
Accession Number
ADA133958

Entities

People

  • Raymond Lee Man Wong

Organizations

  • University of Toronto

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Acoustic Propagation
  • Acoustic Properties
  • Acoustic Waves
  • Acoustics
  • Air Force
  • Aircraft Noise
  • Aircrafts
  • Computational Science
  • Fluid Flow
  • Frequency Bands
  • Geometry
  • Integral Equations
  • Jet Engines
  • Measurement
  • Noise Reduction
  • Pressure Measurement
  • Sound Waves

Fields of Study

  • Physics

Readers

  • Acoustics.
  • Fluid Dynamics.