The Rotorcraft Noise Model RNM

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The Rotorcraft Noise Model (RNM)

• Juliet A. Page
• Kenneth J. Plotkin
• Wyle Laboratories
• Wyle Research, Arlington, Virginia
• David A. Conner
• Aeroflightdynamics Directorate (AVRDEC) U.S. Army
  Aviation and Missile Command
• Langley Research Center

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RNM Presentation Roadmap

• Capabilities vehicle acoustic database
• Recent model improvements
• Single track research mode
• Pure tone physics
• Two hemisphere pure tone example
• Single track example
• Multiple track community impact mode
• Future of RNM

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Rotorcraft Noise Model (RNM)

• Atmospheric propagation model which performs an
  acoustic simulation.
• Flight trajectory and vehicle movement is
  defined.
• Acoustic calculations begin with reference noise
  source characteristics defined on a sound source
  hemisphere.

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Measurement or Analytical Database Capabilities

• Sound Source Hemispheres contains broadband data
  for the following vehicles AH-1W, CH-146,
  CH-46E, CH-53E, MV-22B, SH-60B, V-22A, XV-15,
  MD-902, S-76
• (Some data sets are restricted or proprietary)
• Analytically created hemispheres may also be
  used.
• Hemispheres may be defined in terms of broadband
  and pure tone with phase.

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Synchronized Simulation Model

• Substantial code restructuring in 2000.
• Source time based model
• Sound integration calculations streamlined to
  facilitate addition of new metrics.
• Pure tone hemispheric source propagation
  methodology incorporated into RNM

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Single Track Research Mode

• Analytical generation of sound hemispheres for
  research and development purposes
• Vehicle Development
• Operation (Profile / Track) Optimization
• Absolute phase tracking
• Uniform atmosphere
• Straight ray path propagation

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Pure Tone Hemisphere Propagation Capability

• Propagation routines extended to handle pure
  tonal content in addition to one-third octave
  noise.
• Phase propagation components
• Absolute source phase definition (in netCDF file)
• ? phase - start of flight track.
• ? phase source to receiver propagation path
• ? phase ground bounce (Chessels formulation)

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Pure Tone Interference PatternsTwo 100 dB 1000
Hz 100 Ft Hemispheres
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Single Vehicle, Single Track

• CH-53E Super Stallion
• 10 daytime departures
• Flight Track
• Flight Profile

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Data Input

• Location of the flight track.
• Type of aircraft, power and speed settings.
• Number of operations per aircraft per flight
  track.
• Atmospheric properties.
• Yaw, angle of attack, roll And for tiltrotor,
  nacelle angle.
• Terrain (under current development).

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RNM Single Track Operation
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RNM Noise Contour
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TypicalOperations Multiple Vehicles Tracks
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RNMNoiseContours
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Future Enhancements

• Propagation over varying terrain
• Hard vs. Soft
• Non-flat earth
• Improvements to RNM hemisphere interpolation
  procedure
• Flight path angle interpolation
• Longitudinal Accel FPA relationship (x vs. ?)
• Morphing technology
• Urban canyon sound propagation