City Noise Task Force Report

Appendix E

Machines and noise reduction methods

1. Air compressors
   • Available with enclosures, sound insulation and additional soundproofing.
     
   • Note: Many current models (air cooled and water cooled) are available which meet OSHA, NIOSH and WCB regulations on noise levels.
     

2. Rotary blowers: Discharge
   • Use discharge silencers with an internal volume to blower displacement ratio of 18 to 1 or use an absorption type silencer.
     
   • When the blower speed is below the transition speed, use a multichamber type silencer.
     
   • When the blower speed is above the transition speed, use an absorption type silencer.
     

3. Rotary blowers: Intake
   • Use a chamber type silencer with a minimum volume of 15 to 1 or use an absorption type silencer.
     
   • For large, slow-speed blowers, use an absorption type silencer.
     
   • For blowers with operating speeds above the transition speed, use a chamber absorption type silencer.
     
   • Use contra-noise (noise cancellation) to reduce in-duct fan noise.
     

4. Motor vehicle: Operational factors
   • Noise exposure is increased by uphill grades (for heavy trucks and transport vehicles) and by very rough and/or broken pavement surfaces for wheeled vehicles.
     
   • Noise drop-off rate is affected substantially by ground cover.
     
   • Use acoustical construction methods.
     
   • Use contra-noise (noise cancellation) for
     
     • diesel engine and exhaust noise,
       
     • active engine mountings,
       
     • in-car noise reduction through multispeaker systems.
       

5. Fluid power systems (pumps and motors)
   • Use generously-sized pipes on the pump inlet and ensure either good gravity head from the reservoir or a boost pump.
     
   • Use a larger reservoir with baffles to encourage the release of air from the return fluid.
     
   • Fit flexible pipes, where possible, and particularly on the suction side of the pump.
     
   • Consider a pressurized return system.
     
   • Mount pumps and motors on suitable isolators and avoid attaching them to resonant panels.
     
   • Minimize flow restrictions and sudden changes in pipe diameters.
     
   • Fit a pulsation damper or silencer close to the pump.
     
   • Avoid lengths of pipe which are close to the wavelength of the pump pulsations or to its multiples.
     
   • Choose valves, motors and pumps that have been designed to minimize pressure pulsations.
     
   • Consider the design of an enclosure around the noisy pumps and valves.
     
   • Use isolating pipe clamp.
     
   • Use servo valves which give a controlled opening and closing, thus avoiding pressure transients.
     

6. Aircraft
   • Use of contra-noise (noise cancellation) is effective on jet engines.
     

7. Air distribution systems
   • Reduce strength of the primary source (the fan).
     
   • Attenuate fan noise in the main trans mission path (duct system), between the fan and the area affected.
     
   • Ensure all sound generated by second sources is kept down to a level which is insignificant compared with the level of fan noise, silenced or unsilenced, at that part of the system.
     
   • Eliminate the transmission of all flanking and indirectly produced energy.
     

8. Piling equipment: Pneumatic/diesel hammer or steam winch vibrator driver
   • Enclose hammer head and top pile in acoustic screen.
     
   • Acoustically dampen sheet steel piles to reduce vibration and resonance.
     
   • Alternative a: different method of piling.
     
   • Alternative b: Different methods of soil retention and ground improvements, e.g., diaphragm walls, ground anchors, shafts formed of pre-cast concrete segments sunk into the ground under Kentledge, use of pre-treatments prior to excavation, such as dewatering, freezing soil, injection, etc.
     

9. Piling equipment: Impact on pile
   • Use resilient pad (dolly) between pile and hammer head, e.g., two layers of absorbent cloth stuffed with glass fibre or mineral wool and protected by plywood.
     
   • Packing should be kept in good condition.
     

10. Piling equipment: Crane cables, pile guiders and attachments
    • Carefully align the pile and rig.
      

11. Piling equipment: Power units or base machines
    • Fit more efficient silencer or exhaust.
      
    • Acoustically dampen panel and covers.
      
    • When intended by the manufacturer, engine panels should be kept closed.
      
    • Use acoustic screens where possible.
      

12. Bulldozer, compactor, crane, dump truck, excavator, grader loader, scraper shovel: Engine noise
    • Fit more efficient silencers or exhaust.
      
    • Enclosure panels, when fitted, should be kept closed.
      

13. Compressor, generator: Engine noise
    • Fit more efficient exhaust silencer.
      
    • Acoustically dampen metal casings.
      
    • Enclosure panels should be kept shut.
      
    • Screen the unit.
      
    • Alternative a: Use electric motor in preference to diesel or petrol engine for compressors.
      
    • Alternative b: If there is no mains supply, a sound-reduced compressor or generator can be used to supply several pieces of plant.
      
    • Alternative c: Use centralized generator system.
      

14. Pneumatic concrete breaker: Tool
    • Fit a muffler; this will reduce the noise without impairing efficiency.
      
    • Use the breaker insider a portable acoustic enclosure.
      
    • Alternative a: Use rotary drill and burster.
      
    • Alternative b: Hydraulic and electric tools are available.
      
    • Alternative c: A thermic lance can be used to burn through large sections of concrete; any reinforcement helps the burning process.
      
    • Alternative d: For breaking large areas of concrete, equipment which breaks concrete in bending could be used.
      

15. Pneumatic concrete breaker: Bit
    • Use dampen bit to eliminate "ringing". (Little noise once surface is broken.)
      

16. Pneumatic concrete breaker: Air line
    • Leaks in air line should be sealed.
      

17. Pneumatic concrete breaker: Motor
    • Fit muffler to pneumatic saws.
      

18. Power saws: Vibration of blade or material being cut
    • Keep saw sharp.
      
    • Use a damped blade.
      
    • Clamp material while cutting with packing, if necessary.
      

19. Rotary drills, diamond drilling/boring: Drive motor and bit
    • Use machine inside an acoustic cover.
      

20. Riveters
    • Enclose working area within acoustic screen.
      

21. Cartridge gun
    • Use a sound-reduced gun.
      
    • Alternative: Drilled fixings.
      

22. Pump: Engine pulsing
    • Enclose in acoustic screen (but allow for engine cooling and exhaust.)
      

23. Batching plant concrete mixer: Engine
    • Fit more efficient silencer on diesel or gas engine.
      
    • Enclose engine.
      
    • Locate static mixing plant as far as possible from those likely to be inconvenienced by the noise.
      

24. Batching plant concrete mixer: Filling
    • Do not let aggregate fall from an excessive height.
      

25. Batching plant concrete mixer: Cleaning
    • Do not hammer the drum.
      

26. Hammer
    • Use a nailing machine.
      
    • Alternative: Use screws
      

27. Electric impact chisel
    • Rotary hand milling machine.
      

28. Materials handling
    • Do not drop materials from a height.
      
    • Screen dropping zones, especially on conveyor systems.
      

29. Steam cleaning
    • Pass escaping steam through a silencer or screen outlet zone.
      

30. Transformers
    • Use new high-efficiency transformers with low electrical losses.
      
    • Use high-efficiency low-speed cooling fans and mufflers.
      
    • Use barrier walls, partial or full enclosures.
      
    • Relocate transformer.
      

31. Outdoor appliances (heat pumps, air conditioners, pool filters)
    • Select a quieter appliance.
      
    • Move the unit to a better location.
      
    • Use a barrier or enclosure unless the problem is low-frequency noise.
      
    • Do not locate the appliance between closely-spaced buildings or under a carport or large overhang.
      

32. Industrial fans (inlet and outlet)
    • Orient the outlet or inlet so that it points at a 45 degree or greater angle away from critical areas.
      
    • Use ducted and muffled inlets and outlets.
      
    • Use combined thermal and acoustical insulation lagging.
      
    • Use an enclosure.
      
    • Use dissipative, parallel-baffle, open-cavity type mufflers.
      
    • Use flue gas scrubbers, filters, or precipitators between induced-draft fan and its stack.
      
    • Use variable-speed fans to reduce nighttime noise.
      
    • Use well-designed and proper-sized ducts.
      

33. Condensers and cooling towers
    • Reposition or re-orient the equipment in open air.
      
    • Use quieter equipment.
      
    • Use silencers and mufflers.
      
    • Reduce fan speed during night.
      
    • Install wide-chord, high-efficiency fan blades.
      
    • Use centrifugal fans rather than propeller fans.
      
    • Install barriers and partial enclosures, but do not excessively restrict air flow.
      

34. Boilers
    • Install metal plate divider(s) to subdivide the interior of the boiler.
      
    • Use a well-insulated exterior enclosure.
      

35. Gas turbines
    • Use conventional parallel-baffle or tubular muffler with closely spaced thin baffles on compressor inlet.
      
    • Design inlet ducting, plenum walls, expansion joints and access hatches to contain noise and avoid flanking radiation.
      
    • Use parallel or tubular mufflers on outlets.
      
    • Use heat recovery steam generators with spaced out insulation laggings to attenuate exhaust noise.
      
    • Use high-performance low-speed fan blades, mufflers or partial enclosures.
      

36. Large steam generators
    • Use equipment with noise abatement features.
      
    • Reduce building reverberation by using siding with a fibrous insulation sandwiched between a perforated metal inner surface and solid exterior surface.
      

37. Diesel-powered equipment
    • Use mufflers in good working condition.
      
    • Operate equipment at its rated speed and power.
      

38. Trucks and tractors
    • Use parts that are made from naturally dampened material.
      
    • Use crankcase and water jacket panels.
      
    • Redesign injectors and combustion chambers to give smoother burn.
      
    • Encapsulate the engine.
      
    • Use a proper fan shroud to direct air flow through the fan.
      
    • Install engine mounts with vibration isolators.
      
    • Use inlet/outlet attenuators, mufflers, silencers.
      
    • Use turbocharger equipped with attenuators to reduce high-frequency noises.
      
    • Use improved cab design.
      
    • Use quiet valves and blow-off attenuators.
      
    • Use a "Whispertrim" to reduce noise from the pressure drop across the valve.
      

39. Motor vehicles/traffic factors
    • Use barriers and/or berms.
      
    • Use proper site design techniques.
      
    • Use acoustical construction methods.
      
    • Use traffic calming measures.
      

(Noise is increased by uphill grades, especially for heavy transport vehicles and larger transport vehicles, and by very rough pavement surfaces. Noise transmission is decreased by buildings, landforms and other barriers. Noise drop-off rate is affected substantially by type of ground cover.)

Last modified: April 30, 1997
(c) 1996 City of Vancouver