Separation of main and tail rotor noise sources from ground-based acoustic measurements using time-domain de-Dopplerization

Eric Greenwood, Fredric H. Schmitz

Research output: Chapter in Book/Report/Conference proceedingConference contribution

10 Citations (Scopus)

Abstract

A new method of separating the contributions of helicopter main and tail rotor noise sources is presented, making use of ground-based acoustic measurements. The method employs time-domain de-Dopplerization to transform the acoustic pressure time-history data collected from an array of ground-based microphones to the equivalent time-history signals observed by an array of virtual inflight microphones traveling with the helicopter. The now-stationary signals observed by the virtual microphones are then periodically averaged with the main and tail rotor once per revolution triggers. The averaging process suppresses noise which is not periodic with the respective rotor, allowing for the separation of main and tail rotor pressure time-histories. The averaged measurements are then interpolated across the range of directivity angles captured by the microphone array in order to generate separate acoustic hemispheres for the main and tail rotor noise sources. The new method is successfully applied to ground-based microphone measurements of a Bell 206B3 helicopter and demonstrates the strong directivity characteristics of harmonic noise radiation from both the main and tail rotors of that helicopter.

Original languageEnglish (US)
Title of host publication35th European Rotorcraft Forum 2009, ERF 2009
Pages101-112
Number of pages12
StatePublished - Dec 1 2009
Event35th European Rotorcraft Forum 2009, ERF 2009 - Hamburg, Germany
Duration: Sep 22 2009Sep 25 2009

Publication series

Name35th European Rotorcraft Forum 2009, ERF 2009
Volume1

Conference

Conference35th European Rotorcraft Forum 2009, ERF 2009
CountryGermany
CityHamburg
Period9/22/099/25/09

Fingerprint

Time measurement
Acoustic noise
Microphones
Rotors
Acoustics
Helicopters
Radiation

All Science Journal Classification (ASJC) codes

  • Aerospace Engineering
  • Automotive Engineering

Cite this

Greenwood, E., & Schmitz, F. H. (2009). Separation of main and tail rotor noise sources from ground-based acoustic measurements using time-domain de-Dopplerization. In 35th European Rotorcraft Forum 2009, ERF 2009 (pp. 101-112). (35th European Rotorcraft Forum 2009, ERF 2009; Vol. 1).
Greenwood, Eric ; Schmitz, Fredric H. / Separation of main and tail rotor noise sources from ground-based acoustic measurements using time-domain de-Dopplerization. 35th European Rotorcraft Forum 2009, ERF 2009. 2009. pp. 101-112 (35th European Rotorcraft Forum 2009, ERF 2009).
@inproceedings{43f41ff244054cc7a78ac82bd5b5a345,
title = "Separation of main and tail rotor noise sources from ground-based acoustic measurements using time-domain de-Dopplerization",
abstract = "A new method of separating the contributions of helicopter main and tail rotor noise sources is presented, making use of ground-based acoustic measurements. The method employs time-domain de-Dopplerization to transform the acoustic pressure time-history data collected from an array of ground-based microphones to the equivalent time-history signals observed by an array of virtual inflight microphones traveling with the helicopter. The now-stationary signals observed by the virtual microphones are then periodically averaged with the main and tail rotor once per revolution triggers. The averaging process suppresses noise which is not periodic with the respective rotor, allowing for the separation of main and tail rotor pressure time-histories. The averaged measurements are then interpolated across the range of directivity angles captured by the microphone array in order to generate separate acoustic hemispheres for the main and tail rotor noise sources. The new method is successfully applied to ground-based microphone measurements of a Bell 206B3 helicopter and demonstrates the strong directivity characteristics of harmonic noise radiation from both the main and tail rotors of that helicopter.",
author = "Eric Greenwood and Schmitz, {Fredric H.}",
year = "2009",
month = "12",
day = "1",
language = "English (US)",
isbn = "9781615678747",
series = "35th European Rotorcraft Forum 2009, ERF 2009",
pages = "101--112",
booktitle = "35th European Rotorcraft Forum 2009, ERF 2009",

}

Greenwood, E & Schmitz, FH 2009, Separation of main and tail rotor noise sources from ground-based acoustic measurements using time-domain de-Dopplerization. in 35th European Rotorcraft Forum 2009, ERF 2009. 35th European Rotorcraft Forum 2009, ERF 2009, vol. 1, pp. 101-112, 35th European Rotorcraft Forum 2009, ERF 2009, Hamburg, Germany, 9/22/09.

Separation of main and tail rotor noise sources from ground-based acoustic measurements using time-domain de-Dopplerization. / Greenwood, Eric; Schmitz, Fredric H.

35th European Rotorcraft Forum 2009, ERF 2009. 2009. p. 101-112 (35th European Rotorcraft Forum 2009, ERF 2009; Vol. 1).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

TY - GEN

T1 - Separation of main and tail rotor noise sources from ground-based acoustic measurements using time-domain de-Dopplerization

AU - Greenwood, Eric

AU - Schmitz, Fredric H.

PY - 2009/12/1

Y1 - 2009/12/1

N2 - A new method of separating the contributions of helicopter main and tail rotor noise sources is presented, making use of ground-based acoustic measurements. The method employs time-domain de-Dopplerization to transform the acoustic pressure time-history data collected from an array of ground-based microphones to the equivalent time-history signals observed by an array of virtual inflight microphones traveling with the helicopter. The now-stationary signals observed by the virtual microphones are then periodically averaged with the main and tail rotor once per revolution triggers. The averaging process suppresses noise which is not periodic with the respective rotor, allowing for the separation of main and tail rotor pressure time-histories. The averaged measurements are then interpolated across the range of directivity angles captured by the microphone array in order to generate separate acoustic hemispheres for the main and tail rotor noise sources. The new method is successfully applied to ground-based microphone measurements of a Bell 206B3 helicopter and demonstrates the strong directivity characteristics of harmonic noise radiation from both the main and tail rotors of that helicopter.

AB - A new method of separating the contributions of helicopter main and tail rotor noise sources is presented, making use of ground-based acoustic measurements. The method employs time-domain de-Dopplerization to transform the acoustic pressure time-history data collected from an array of ground-based microphones to the equivalent time-history signals observed by an array of virtual inflight microphones traveling with the helicopter. The now-stationary signals observed by the virtual microphones are then periodically averaged with the main and tail rotor once per revolution triggers. The averaging process suppresses noise which is not periodic with the respective rotor, allowing for the separation of main and tail rotor pressure time-histories. The averaged measurements are then interpolated across the range of directivity angles captured by the microphone array in order to generate separate acoustic hemispheres for the main and tail rotor noise sources. The new method is successfully applied to ground-based microphone measurements of a Bell 206B3 helicopter and demonstrates the strong directivity characteristics of harmonic noise radiation from both the main and tail rotors of that helicopter.

UR - http://www.scopus.com/inward/record.url?scp=77952325138&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77952325138&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:77952325138

SN - 9781615678747

T3 - 35th European Rotorcraft Forum 2009, ERF 2009

SP - 101

EP - 112

BT - 35th European Rotorcraft Forum 2009, ERF 2009

ER -

Greenwood E, Schmitz FH. Separation of main and tail rotor noise sources from ground-based acoustic measurements using time-domain de-Dopplerization. In 35th European Rotorcraft Forum 2009, ERF 2009. 2009. p. 101-112. (35th European Rotorcraft Forum 2009, ERF 2009).