The results of an experimental investigation into the narrow band frequency content of the surface vibration of a particular four cylinder, water-cooled, indirect injection diesel engine are described. The long term objective, of which the work reported here is a part, is the reduction of noise emission at source. Noise is radiated from the engine as a result of surface vibration. The characteristics of surface vibration are described and an explanation is given of why the discrete frequency response of the engine has hitherto appeared to be broad band in nature. The relationship of the pure tone response to the combustion pressure spectrum is also described. The vibration of the engine side wall has the greatest amplitude in the frequency band 2.9 - 3.8 khz, irrespective of engine speed and load, which could be a result of piston slap. The vibration of the crankcase skirt, in contrast, is more or less uniform throughout the frequency range 0 - 5 khz, relecting the great difficulty in achieving a significant reduction in the overall level at this location. The low frequency pressure spectrum is shown to have roughly a 47 db/decade decline in amplitude with frequency below 800 hz, in comparison with an oft-quoted figure of 30 db/decade. Significant differences between no load and half load pressure spectra are shown to exist. /Author/TRRL/

  • Availability:
  • Corporate Authors:

    Academic Press Incorporated

    Berkeley Square House, Berkeley Square
    London W1,   England 
  • Authors:
    • Marples, V
  • Publication Date: 1977-6-8


  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00163965
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: Analytic
  • Files: ITRD, TRIS
  • Created Date: Dec 8 1977 12:00AM