Rank: Forum user 
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We have been checking noise levels of some new machinery , to find one particular machine reads regularly over 90db , this is only used to cut cloth material and is actually a very quite machine , however due to the Sonic cutter on it , the noise level meter reads over 90db , yet no one can actually hear the noise from it due to the pitch of the noise ( similar to a dog whistle I suppose , being out of the normal hearing range)
So my question is , although we can not physically hear the noise , but it is registered on a noise reader , would we have to enforce hearing defenders due to the high reading.
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Rank: Super forum user
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I am sure the actual regulations refers to audible sound.
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Rank: Forum user
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Hi,
If you have set your meter to normal hearing range i.e. 1000 - 1500hz the reading will be within the hearing range - if you have completed octave band analysis, then all ranges up to 21000hz will be covered, either way mandatory hearing protection will be required because all levels of over exposure can have detrimental affect on the cilia within the ear canal.
Pete,
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Rank: Forum user
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Alfasev wrote:I am sure the actual regulations refers to audible sound. yes I agree it does state Noise is an audible sound , hence why I considered us not at risk , but still needed to consider any damage caused to the ears even though we may not be able to actually hear the noise.
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Rank: Forum user
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To clarify 20 - 21000hz is the typical hearing range of a young person, but this deteriorates with age, as stated 1000hz to around top end of 5000hz are frequencies we normally respond to / hear efficiently.
Pete,
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Rank: Forum user
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Thanks Pete , and sorry for sounding a bit dim, are you saying with this issue , even though we may not be able to hear the noise from the Sonic cutter we should make hearing defence mandatory due to the fact the noise meter is picking up the noise to be around the 90db level , as the operators are exposed for a number of hours per day.
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Rank: Forum user
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Hi,
If the noise emitted is within the ranges identified in my previous mail then yes you will need to manage or reduce the exposure,
Pete,
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Rank: Super forum user 
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Hi Have you considered using noise dose badges? As you have measured the noise levels as part of a risk assessment and have identified a potential risk to hearing, you should then measure the exposure. You can hire dose badges that will measure the noise exposure in the human hearing range (dBA) and the peak pressure exposure (dBC). They will also time weight it for you. If you do have a problem then you need to look at engineering controls before looking at hearing protection. Check out the HSE site on noise risk assessment. http://www.hse.gov.uk/noise/risks.htmIan
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Rank: Forum user
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Rank: Super forum user
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Hi pato,
What are you using to measure the machinery noise? The measurement needs a filter applied to it which makes it sensitive at different frequencies in approximately the same way as adult human hearing. The filter normally used is called A-weighting and the measurement you end up with should be displayed on the device as dB(A), dBA, LAeq=xx or something similar - basically there should be a capital A in it.
It sounds like that's not happening with your own measurement.
If you tell us how you got the measurement we can help you make sure it's usable. Good luck.
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Rank: Forum user
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And remember the noise level has to be over the lower threshold spread over an eight hour period (TWA) for controls to be necessary, short term exposure may not trigger the need to impose control measures.
Pete,
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Rank: Forum user
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thanks everyone for your help & comments , we have managed to add soundproofing around the casing of the cutter , which has resolved the issue.
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Rank: Super forum user
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Out of interest pato1969 did you manage to record the frequency (Hz) of the sound and what if any information did the manufacture or importers give you.
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