NCHRP Report 635: Acoustic Beamforming: Mapping Sources of Truck Noise
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NCHRP Report 635:
Acoustic Beamforming: Mapping Sources of Truck Noise
(2009)
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Overview

Authors

Description

TRB's National Cooperative Highway Research Program (NCHRP) Report 635: Acoustic Beamforming: Mapping Sources of Truck Noise explores the acoustic beamforming technique in an attempt to pinpoint and measure noise levels from heavy truck traffic. The beamforming technique uses an elliptical array of more than 70 microphones and data acquisition software to measure noise levels from a variety of noise sources on large trucksâ€"including the engine, tires, mufflers, and exhaust pipes.

Topics

  • Transportation — Highways
  • Transportation — Motor Carriers
  • Transportation — Environment
  • Transportation — Pavements
  • Transportation — Vehicles and Equipment

Publication Info

89 pages | 8.5 x 11
Contents

Table of Contents

skim chapter
Front Matter i-ix
Summary 1-5
1.2 Heavy Truck Noise Sources 6-6
1.3 Source Identification Methods 7-8
1.4 Objective and Scope of Research 9-9
Task 5. Execute Testing Plan 10-10
Task 9. Submit Final Report 11-11
3.2.1 Noise Mapping Technique Development 12-12
3.2.2 Microphone Array Design 13-13
3.2.3 Balance Between Array Aperture and Spherical Spreading Loss 14-16
3.2.4 Design Conclusions 17-18
3.3.3 Preliminary Testing 19-19
3.4.1 Low-Speed Tests 20-21
3.4.2 High-Speed Tests 22-22
3.4.3 Passby and Intensity Measurements 23-30
3.5.1 Beamformer Calibrations with Spherical Source 31-33
3.5.2 Benchmark Measurements of Spherical Source on Moving Truck with Competing Truck Noise 34-34
3.5.3 Benchmark Parallel Array-Based and Acoustic Intensity Measurements for Stationary Trucks 35-40
3.5.4.1 Analysis Technique for Low- and High-Speed Track Passbys 41-43
3.5.4.2 Passby Evaluations of the 5900i Truck: Localization of Engine Compartment and Tire Noise 44-45
3.5.4.3 Passby Evaluations of the 9200i Truck: Localization of Engine Compartment and Exhaust Noise 46-47
3.5.4.4 Evaluations of the Truck Acoustic Source Level During Passby as a Function of Vertical Elevation 48-52
3.6.2 Data Post-Processing Algorithm Modifications 53-53
3.6.4 Roadside Measurement Setup 54-54
3.7.2 Image Results of the Vehicle Passbys 55-67
3.7.3 Example Model of Truck Sources for Simulating Noise Propagation Results of the Vehicle Passbys 68-70
4.2 Recommendations 71-72
References 73-74
Appendix A - Array Microphone Coordinates 75-75
Appendix B - Vertical Distributions of Noise Sources for Heavy Trucks 76-77
Appendix C - Glossary of Special Terms 78-79
Abbreviations used without definitions in TRB publications 80-80

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