Noise management data sheets: Rotary lawn mower
Rotary Mowers range in noise levels from 84 to 94 dB(A) depending on engine type (4-stroke or 2-stroke) and condition and operating speed. Because the noise levels of a Rotary Mower can exceed 85 dB(A), personal hearing protection is normally used.
- Ensure all covers are securely fastened.
- Ensure the muffler is in good condition (no holes) and is bolted firmly to the side of the engine.
- Ensure throttle control is in good working order and regulates the revs of the machine in a smooth manner. Some mowers (mostly 2-stroke) have a plastic carburettor body and if not serviced regularly, can suffer from the cam and lifter assembly within the carburettor sticking.
- Ensure that blades are free running (not hitting against guards) and not worn down.
- Maintain lawnmower to ensure efficient running and easy starting.
- Machines that do not operate efficiently require higher revs and make more noise.
- The noise level of a four stroke lawnmower can be reduced by fitting a "Low Tone" muffler to the engine. These mufflers reduce noise levels by approximately 3dB(A) more than the standard mufflers and are available from most mowing equipment suppliers.
- Do not "over rev" machine. Use only enough power to perform the work.
- Mark normal operating revs on throttle control.
- With 2-stroke powered mowers, ensure that the correct petrol/oil mixture is used. Lack of oil in the mixture will cause the engine to "rattle" more due to insufficient lubrication of the main and big end bearings.
- Ensure staff are adequately trained in correct use of the lawnmower.
- On replacement, specify and purchase a four-stroke mower (these tend to be quieter) fitted with a low tone muffler. Test run several different types of mower and take the noise levels into consideration when making your final choice.
- There are two types of blade holders found on rotary mowers, the straight bar type and the disc blade holder. Most Australian manufacturers use the blade disc, which is the quieter of the two. Some imported mowers are fitted with the cheaper and noisier straight bar type.
Adapted from the Noise Control Manual for Schools with the permission of the Education Department of Western Australia.