Atmospheric Turbulence Decorrelation Through Porous Material Interactions

Abstract

It is commonly assumed that microphone windscreens reduce wind noise by averaging pressure distributed homogeneously over the windscreen surface. If this theory were valid, the surface pressures would average out in such a manner that the noise spectrum at low frequencies would approach that of an unscreened microphone. Experimental observations contradict this, and wind noise reduction (WNR) is observed even at infrasonic frequencies. We hypothesize that distortion of turbulence by a solid porous object alters the statistics of turbulent pressure received inside the object, in a manner directly related to the porous material properties. We will extend fundamental equations for turbulent distortion around nonporous objects to formulate a new approximation for flow impinging on a porous object, which will be tested against experimental work in a wind tunnel, and further verified in atmospheric turbulence.

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Document Details

Document Type
Technical Report
Publication Date
Oct 26, 2020
Accession Number
AD1187000

Entities

People

  • Gordon M. Ochi

Organizations

  • Engineer Research and Development Center

Tags

DTIC Thesaurus Topics

  • Acquisition
  • Atmospheric Motion
  • Computer Programming
  • Copyrights
  • Data Acquisition
  • Data Management
  • Data Sets
  • Economic Security
  • Intellectual Property
  • Internal Pressure
  • Law
  • Materials
  • Measurement
  • Microphones
  • Noise Reduction
  • Operating Systems
  • Porous Materials
  • Programming Languages
  • Security
  • Standards
  • Wind
  • Wind Direction
  • Wind Tunnels

Fields of Study

  • Physics

Readers

  • Acoustics.
  • Atmospheric Science / Meteorology, specifically Wind Wave Turbulence.
  • Surface Engineering/Surface Coating Technology.