Solving Noise Issues through Maintenance

Good maintenance reducing the physical hazard of noise. | Legal Obligations | Maintenance - a High Risk Activity| Provision of Appropriate Equipment

Check with the operator of equipment or machinery that the noise level has not increased over time. If it has it this is an indication that the machine requires attention. Have a reporting system in place so the operator can inform of problems.

Check that the noise-control features fitted to the machine have not deteriorated or been removed.   

In many cases, a noise hazard will be created or made worse by lack of maintenance. Parts may become loose, creating more noise because of improper operation or scraping against other parts. Grinding noises may also occur as the result of inadequate lubrication. It is especially important to provide proper maintenance of noise control devices which are added or built into machinery. Loose or worn parts should be fixed as soon as possible.

Always check and see if there are any problems starting to appear with a machine or equipment. Check for signs of wear or if the machine’s performance is down. Some problems will appear as looseness or increased vibration. Listen for new noises, especially tonal “whining” sounds, repeated impacts, or high frequency “screech” sounds. Also, slipping belts will cause a screech at start up, while a damaged bearing may appear as a “clunk” during run down.

Ideally, the workplace should have a system in place for checking and servicing the various machines and power tools.

Why Machines Get Noisier With Use

  • Machines get nosier with use because:
  • worn or chipped gear teeth - will not mesh properly, the shiny wear marks are often visible on the teeth
  • worn bearings - bearing wear creates vibration and noise, as flat spots or cracks appear in the balls
  • slackness between worn or loose parts - causes rattling noises, squealing from slack drive belts, “piston slap” in motors, air leaks, etc.
  • poor lubrication - causes squeaking noises due to friction or impact noise in dry and worn gears or bearings
  • imbalance in rotating parts - imbalances with fan impellers or motor shaft will show up as excess vibration and noise
  • obstruction in airways - a build-up of dirt or a bent/damaged piece of metal in an airway or near a moving part, e.g. a bent fan guard, can cause whistling or other “air” type noise
  • blunt blades or cutting faces - blunt or chipped saw teeth, drill bits, router bits etc, usually make the job noisier as well as slower
  • damaged silencers - silencers for air-driven machines or mufflers for engines may become clogged with dirt, rusted or damaged, so losing their ability to absorb noise and
  • removal of a noise-reducing attachment - mufflers, silencers, covers, guards, vibration isolators etc. which reduce noise should never be removed except during maintenance and then must be replaced.

Examples of Noise Reduction By Maintenance

1. A common type of reciprocating air compressor produced 94 dB(A) at 1 metre.

  • Regrinding the valve to improve the seal resulted in a significant noise reduction of approximately 7 dB(A).        
  • Introducing an oil additive gave an extra 1 dB(A) reduction.

The overall noise reduction due to the re-seating of the valve and the introduction of the oil additive is therefore estimated to be approximately 8 dB(A). This is significant, in that the reduction was achieved at minimal cost, using methods which could be adopted by a skilled maintenance trades person.

(reference; WorkSafe Western Australia, “Noise Control Case Study: - Reduction of Noise from a Reciprocating Compressor through Maintenance, 1999”.)

2. A band saw with a typical noise level of 90-105 dB(A).

Maintenance of machine (e.g. pulley scrapers, lubricating felt pads or sawdust extraction system) and blade, combined with blade adjustment, are extremely important for noise levels.

3. A multi-spindle planning and moulding machine with a typical noise level of up to 105 dB(A).

Properly designed and maintained chip extraction systems (where not part of integral enclosure) will reduce idling noise levels. A noise enclosure could be provided and if properly maintained will further reduce the noise level.