Investigation of the Vortex Noise Produced by a Helicopter Rotor

Abstract

Karman-street-type vortex shedding from a lifting surface was analyzed as a source of noise from a helicopter rotor in hover and forward flight. Experimental pressure-time histories were analyzed, and high resolution spectra were developed over a frequency range of 0 to 5000 Hz using a 0.7-Hz filter. The results of the investigation indicated that 'vortex noise' is the major source of acoustic radiation from a helicopter rotor in hover or low-speed flight and that it is concentrated in the frequency range of 200 to 500 Hz.

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Document Details

Document Type
Technical Report
Publication Date
Feb 01, 1972
Accession Number
AD0741778

Entities

People

  • H. K. Johnson
  • Walter M. Katz

Tags

Communities of Interest

  • Air Platforms

DTIC Thesaurus Topics

  • Acoustic Propagation
  • Acoustic Signals
  • Acoustics
  • Aircrafts
  • Airframes
  • Boundary Layer
  • Contracts
  • Data Analysis
  • Doppler Effect
  • Experimental Data
  • Helicopter Rotors
  • Helicopters
  • High Resolution
  • Mach Number
  • Measurement
  • Recording Systems
  • Tail Rotors

Fields of Study

  • Physics

Readers

  • Aerodynamics.
  • Phased Array Antenna Design.
  • Speech Processing/Speech Recognition.