Present European noise limits for heavy diesel vehicles are 89 dba for 200 hp, and 91 dba above. Actual engine noise damped by 1. Control of valve timing, injection and combustion, 2. Design alterations to raise the engine's natural frequency, 3. Fitting of external insulation, 4. Complete encapsulation. The first method produces very slight attenuation but the others can produce reductions of about 10 dba. Where the engine or engine space is insulated, problems arise in cooling; on total encapsulation fan and radiator must be outside engine space. Limited damping is possible by enclosing radiator, fan and engine in an insulation tunnel. Fan noise is rpm dependent and damping must be based on continuous thermostatic control to reduce fan speed. Combination of reflection and absorption silencers can reduce silencer noise. A test lorry was fitted with 1. Tunnel insulation for radiator, fan and engine, 2. Absorbent top of tunnel, 3. Fan with continuous thermostatic rpm control, 4. Dual combined silencers. Noise level of standard vehicle was 91 dba, that of test vehicle about 81. Practical minimum is however 86. Full encapsulation is possible on urban buses with rear engine, noise level being 77 dba. Damping efforts should be internationally coordinated to assist exports. /TRRL/

  • Corporate Authors:

    Svenska Vagforeningen

    Fridhemsgatan 15
    11240 Stockholm K,   Sweden 
  • Authors:
    • Roennhult, J
  • Publication Date: 1975


  • Swedish

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00132228
  • Record Type: Publication
  • Source Agency: Swedish National Road and Transport Research Institute (VTI)
  • Files: TRIS
  • Created Date: Jun 23 1976 12:00AM