VEHICLE NOISE SOURCES AND NOISE-SUPPRESSION POTENTIAL

A study was made of the noise sources of a heavy-duty diesel tractor trailer. By making measurements at 50 ft (15 m) to the side of the vehicle, it was found that: (1) truck engine noise produced by the rapid pressure rise in the combustion chambers of such engines is radiated by the vibrations of the engine block and attached fixtures, with a sound level of 78 dBA being attributed to the engine and mechanical combustion noise sources; (2) exhaust noise is engine noise is engine noise radiated from the exhaust pipe outlet and vibration noise of the pipes and mufflers, and a level of 85 dBA represents typical exhaust noise; (3) engine air intake or induction noise at a relatively low level of 75 dBA is created by the pulsating column of air moving into the engine and, in many cases, includes noise of mechanically driven or exhaust turbine-driven supercharges; (4) the engine cooling fan moves large quantities of air through the radiator with a very restricted downstream flow condition and generates high noise levels (82 dBA); and (5) truck tires generate a noise level of 75 dBA at a speed of 35 mph (56 km/h) or less and 95 dBA at highway speeds. Adding all sources gives a total truck noise level of 88 dBA at speeds less than 35 mph (56 km/h) and 96 dBA at highway speeds. These data would apply to a relatively modern truck design that is in compliance with voluntary industry standards and noise regulations of various states and localities. Measurements were also made on passenger car noise and motorcycle noise; these results are presented and discussed. In addition, discussions are made of noise certification levels, sound propagation, atmospheric attenuation, traffic noise, and highway noise barriers. Tables are presented on the following: Percentage of people annoyed by the sources of residential noise; population and use of mobile noise sources in the U.S.; miles traveled by motor trucks; California motor vehicle noise certification levels at 50 ft (15 m); effect of noise-abatement measures on highway noise; and relation of quieting truck and using roadside barriers to reduce truck noise.

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  • Supplemental Notes:
    • Presented at a Workshop on motor Vehicle Noise Control, Washington, D.C., 10-11 December 1974. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
  • Corporate Authors:

    Transportation Research Board (TRB)

    Washington, DC   
  • Authors:
    • Close, W H
    • Wesler, J E
  • Conference:
  • Publication Date: 1975

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 14-33
  • Monograph Title: Motor vehicle noise control
  • Serial:

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Filing Info

  • Accession Number: 00098522
  • Record Type: Publication
  • Files: TRIS, TRB, ATRI
  • Created Date: Aug 27 1975 12:00AM