noise

							           Noise Reduction Research

                  Bill Willshire

                  Home & Home
             Langley Research Center
               November 16, 1999       AT
H&Hnr-vk
           Noise Reduction
               Program Drivers



                   Environmental
                      Concern
                   • Quality of Life
                   • Public Good

  Increased                              Improved
   Capacity                            Competitiveness
• Enables Growth                        • Balance of Trade
• Public Good                           • Public Good
                          Noise Reduction
                    Progress in Noise Reduction

            120




   Sideline 110
    Noise
    Level,
    EPNdB
(1500’ Sideline)
            100
                                                                     A321
                                                                     A330
                                                                     777-200
                                                                     MD90-30

             90
                   1950   1960        1970         1980     1990   1995
                                 Year of Initial Service
• Without new noise reduction technology, increasing demand coupled with
increasing population will result in increased community noise impact.
                    Noise Reduction
             Current Program Objective and Scope
Objective:
• 10 dB Community Noise Impact Reduction Relative to 1992
  Production Technology
Scope:
• A broad, $200M joint program with the FAA
• Initiated in FY1994, ends in FY2001
• Technical program is result of an extensive NASA inter-center,
  FAA, and industry partnership.
 Note: With the termination of the Advanced Subsonic
 Technology Program in FY00, the Noise Reduction Element was
 transferred to the Aerospace Vehicle Systems Technology
 Program
                              Noise Reduction
               Current Program Management Structure

                               Aerospace Vehicle Systems
                                  Technology Program                    Industry/Government
                               NASA Langley Research Center             Steering Committee
                                  Darrel Tenney, Director

                                                                               FAA
                                Noise Reduction Program
                                NASA Langley Research Center             Industry/Government
                                     Bill Willshire, Manager           Technical Working Group
                             Loretta Shaw, GRC; Brian Smith, ARC


  Ames Research Center             Langley Research Center           Glenn Research Center
• Engine Noise Reduction          • Engine Noise Reduction         • Engine Noise Reduction
• Nacelle Aeroacoustics           • Nacelle Aeroacoustics            Dennis Huff
• Airframe Noise Reduction          Joe Posey                      • Nacelle Aeroacoustics
  Clif Horne                      • Airframe Noise Reduction
                                  • Interior Noise Reduction
                                    Rich Silcox                                 Primary
                                  • Community Noise Impact
                                     Kevin Shepherd                              Support
            Noise Reduction
           Engine Noise Reduction

                         • NASA/Allison Low-Noise Fan
                           in Glenn Research Center
                           9’x15’ Wind Tunnel
                         • Demonstrated 3 EPNdB Fan
                           Noise Reduction


Baseline        Swept Stators    Swept/Leaned Stators
                   Noise Reduction
            Flap-edge Airframe Noise Reduction

                                 Airframe noise:
                                     – Today major source on approach
                                     – Tomorrow major source on takeoff
                                     – Components: flap, slat, and gear



CFD/CAA        Model in LTPT*

                                   Flap-edge Airframe Noise Reduction
                                   – Physics-based mechanism
                                     identification
                                   – Source localization
                 Reduction         – Non-intrusive reduction concepts
Mic Array                            discovered and optimized
                                   – 4 dB flap-edge noise reduction

                                          *Langley Research Center Low
                 Frequency, Hz             Turbulence Pressure Tunnel
                     Noise Reduction
         Propulsion Airframe Interaction Experiment
Low Speed Aeroacoustic Facility       Microphone Array Results
           Boeing                                20 kHz
                                                          Jet with Wing


                                  Isolated Jet




                                  • Presence of wing/fuselage
                                   dramatically impacts apparent
                                   noise source
                                  • Jet with wing up to 8 dB nosier
                                  • Interactions not understood and
                                   therefore not exploited
                                Noise Reduction
                  Validation of Noise Prediction Model in Community
                                 Noise Impact Models

                120                                                  • 5001 Departures from DIA
                                                                     • 6 Aircraft Types
Predicted, dB




                100                                                  • ≥ 60 Degrees Above Horizon


                80
                                                                              Contour Plot
                                            Perfect
                                           Agreement
                60



                                                         Predicted, dB
                     60   80         100           120
                           Measured, dB




                                                                                                  10 dB
                                                                             Measured, dB
 National Need for Noise Reduction                                             AT
            Vision
 Objectionable aircraft noise                  Enterprise Noise Goal
  contained within airport
  boundary.                             Reduce the perceived noise levels of future
                                         aircraft by one half (10 dB) from today’s
                                         subsonic aircraft within 10 years, and by
                                         three quarters (20 dB) within 25 years
                  Benefit
 10-year Goal: 65 LDN at airport boundary
 25-year Goal: 55 LDN at airport boundary

                                                 Justification

                          Air transport system is constrained by noise
                          Current planned program will achieve 50% of 10-year goal
                          Broad-based customer support
                          Technology for 2020 and beyond needed soon
                          FAA relies on NASA for long-term noise solutions
                          No national noise program after 2001
                Noise Reduction
                             Benefit
                                                                                      AT
     O’Hare Yearly Average Day Night Level (DNL) Noise Contours
20
                    1997 Baseline
                • Not acceptable
10
                                   20

5                                                     Current Program*
                                                          5 dB Reduction
                                   10
                                                 • Improvement - significant reduction
                                    5            • Does not meet public expectations
                                                 • Constrained growth
20

                                                                             Key
                                                                                    55 dB
10
                                                                                    65 dB
                      10-Year Enterprise Goal
5                                                                               Airport
                          10 dB Reduction
               • 65 dB contour contained within airport                      Scale
               • Enable projected air travel growth                      0   Miles     10
               • Reduce community noise impact
                                                          *TRL 6 relative to 1997
                          Noise Reduction
                           Concluding Remarks
•   Aircraft noise is a critical international environmental issue
     – Very visible public concern in the US
•   Noise will continue to constrain air travel growth until objectionable noise
    contained within airport boundary
•   Current noise reduction program will achieve half of 10-year goal (-5 dB)
•   Slow fleet turnover dictates near-term solution of far-term problems
•   No national noise reduction program exists or is planned for the future
•   Noise reduction research is about public good and enhances quality of life
•   Technical solutions should lead /guide national policy
•   NASA alone of the federal labs has the expertise/capability/track record to
    make the required contributions