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Leanne Claxson  
#1 Posted : 16 May 2025 09:15:54(UTC)
Rank: New forum user
Leanne Claxson

Hello,

I'm hoping someone can explain to me (in very simple terms) how to understand the results from noise meter results, in the sense of when to act accordingly.

A bit of background:

I'm new to a site and noticed that the workshop often has large burst of loud noises, with several employees working in there on the avg.8hr work day period - each usually manning specific machines.

I queried regarding the noise and was informed they do periodic noise meter tests (in-house) and the results average the 70's.

The workshop area houses several large cutting/precision machines and drilling machines for manufacturing components to do with underwater/ship cameras etc.

As the noise levels vary, I thought it was best to carry out noise test monitoring over a week. We've not finished the week yet and if I sample the results with the datalogger - they could vary.

For example, if I sampled 8hrs yesterday - it would tell me:

Max = 95.6

Min = 65.9

Average = 74.4

The avg. over 8hrs meets the regs lower exposure of 80dBa but my question here is: if we have experienced a max of 95.6 in frequent spouradic parts of the day - should we be reacting to that result instead, regardless of the average?

This is where I get confused because they are not exposed to a continuous level of 95.6dBa for 8hrs straight and from previous teachings, I thought you had to be exposed to a certain level continuously for 8hrs (anything exceeding 87 would then be reduced durations if equipment was to remain (obv. having other controls in place also).

The staff currently have ear PPE they can wear too.

Would you agree that this is enough (PPE to wear when needed) if we are just going by the average (though I'd like to make sure that have noise awareness training, depending on the types of machinery they could be handling).

I appreciate any support you can give!

peter gotch  
#2 Posted : 16 May 2025 10:31:52(UTC)
Rank: Super forum user
peter gotch

Hi Leanne

I doubt that you can read much into the data you have collected other than that you appear to have at least one process that is very noisy and producing about 95dB.

For all I know you are using a very cheap meter which might be accurate to say + or - 10dB.

So your 95.6dB could be absolutely horrendous or might be only about 85dB.

But, you haven't explained where the meter or meters were placed when the readings were taken, so I don't know whether a figure of 95.6 is alongside the machine, one metre away at floor level, 5 metres away at ceiling level or whatever. What you need to assess is what is liable to get into a worker's ear!

Nothing wrong with using a simple meter if you know what its limitations are and particularly as an initial diagnositc tool.

It might tell you that there are impact noises which could be easily and cheaply mitigated without recourse to expensive monitoring - at least initially.

At the other end of the scale it should tell you about the processes that you probably shouldn't be too concerned about - well under 80dB(A) even allowing for the tolerance of the measuring equipment.

Might be that you put a datalogger on one person for 8 hours but that their exposure does not give you a picture of what others are exposed to.

If for a minute we assume that the meter is accurate (perhaps tolerance of plus or minus 1dB) and round up your maximum to 96dB(A) - assuming that your meter is actually recording A weighted readings and not (C) or other weighting or some other measurement, then what you need to know is how long someone's ears are exposed to 96dB(A) - even that assumes that the measurement has been taken in an appropriate location!

Rule of thumb (almost exactly correct) - every 3dB(A) increase means a need to halve time and vice versa.

So 96dB(A) for 8 hours means 95 as an eight hour time weighted average (TWA) or Lep,d or Leq(8).

But if only there for 4 hours then their fractional exposure from that job ONLY is still 93dB(A) Lep,d

2 hours, then 90, 1 hour 87,  30 minutes 84dB(A) fractional exposure for the whole 8 hours and so on.

So, let's say this worker is only doing this job for half an hour a day, you have a problem - but it's a problem that is likely greater UNLESS they spend the rest of their day in the office!

So starting point, I suggest, find out about the "meter" and what it can and cannot do (and when it was last calibrated), then check what the reports say about sampling methodology. 

Good luck, Peter

Edited by user 16 May 2025 10:33:52(UTC)  | Reason: Typos

Roundtuit  
#3 Posted : 16 May 2025 10:37:31(UTC)
Rank: Super forum user
Roundtuit

Beware getting caught in averages - the regulations also talk to peak values (with different testing)

https://www.legislation.gov.uk/uksi/2005/1643/regulation/4/made

4.—(1) The lower exposure action values are—

(a)a daily or weekly personal noise exposure of 80 dB (A-weighted); and

(b)a peak sound pressure of 135 dB (C-weighted).

(2) The upper exposure action values are—

(a)a daily or weekly personal noise exposure of 85 dB (A-weighted); and

(b)a peak sound pressure of 137 dB (C-weighted).

(3) The exposure limit values are—

(a)a daily or weekly personal noise exposure of 87 dB (A-weighted); and

(b)a peak sound pressure of 140 dB (C-weighted).

Roundtuit  
#4 Posted : 16 May 2025 10:37:31(UTC)
Rank: Super forum user
Roundtuit

Beware getting caught in averages - the regulations also talk to peak values (with different testing)

https://www.legislation.gov.uk/uksi/2005/1643/regulation/4/made

4.—(1) The lower exposure action values are—

(a)a daily or weekly personal noise exposure of 80 dB (A-weighted); and

(b)a peak sound pressure of 135 dB (C-weighted).

(2) The upper exposure action values are—

(a)a daily or weekly personal noise exposure of 85 dB (A-weighted); and

(b)a peak sound pressure of 137 dB (C-weighted).

(3) The exposure limit values are—

(a)a daily or weekly personal noise exposure of 87 dB (A-weighted); and

(b)a peak sound pressure of 140 dB (C-weighted).

Connor35037  
#5 Posted : 16 May 2025 15:11:44(UTC)
Rank: Forum user
Connor35037

HSE document L108 "Controlling Noise at Work" (free download from their site) will prove useful.

Noise level measured (LAeq) plus duration of noise can be used to give a noise exposure (LEpd).

(See the table on page 41)

Edited by user 16 May 2025 15:12:57(UTC)  | Reason: spelling

Leanne Claxson  
#6 Posted : 21 May 2025 14:25:00(UTC)
Rank: New forum user
Leanne Claxson

Hi all, Sorry it's taken so long to respond - the website doesn't appear to always work for me. Here's a little bit more info to help - more focusing on Peters feedback: "But you haven't explained where the meter or meters were placed when thw readings were taken, so I don't know whether a figure of 95.6 is alongside a machine, one metre away at floor level, 5 metres away at ceiling level or what ever. What you need to assess is what is liable to get into a workers ear!" We placed 1 meter (calibrated) by different machines at table level throughout the workshop and logged it's location, times, durations '"Nothong wrong with using a simple meter if you know what it's limitations are and particularly as an initial diagnostic tool." Yes, this was an in-house reading (indicative) to know if we need a more official reading conducted externally. Were using A-rated readings. The issue with the ear part is the graphs are very sporadic because staff are exposed to high levels of noise in short bursts (so not an 8hr shift at 96dB(A)) - so for example, 1 report may say that the noise went higher than 90 over 13 times in between approx. 3 hrs for short bursts. We are using RS PRO RS-8852 Data Logger Sound Level Meter. Should I base the short bursts to a specific timescale then? So for example, Joe Bloggs can only use X machine for 30 mins at a time.... (if we identify X machine is producing X noise). I apologise for sounding completely dumb on this, I'm not an expert in noise and whilst I've already reached out externally for noise surveys, we need to identify if there's a need for an external survey first. Originally, from what I'm told, an external noise survey was never considered prior to me starting because noises were avg. The 70's but it's like what Rountuit said, to be aware of getting caught up in averages... Once this post is working for me again, I'll look at upload a graph to demonstrate. Thanks for everything so far though - keep it coming because I need all the help! 😅
Kate  
#7 Posted : 21 May 2025 19:54:39(UTC)
Rank: Super forum user
Kate

To determine whether the noise exposure reaches the action levels, you can use the noise calculator on the HSE website.  It's a complicated calculation, which is why they provide the calculator.

What this does is ask you for noise levels and their duration throughout someone's working day.

For example you might input that someone was exposed to 75 dB(A) for 4 hours, to 88 dB(A) for 2 hours and to 98 dB(A) for 1 hour, or whatever it happens to be.

These noise levels should be measured at ear height in the working position. 

The calculator then assigns scores to each interval of exposure and combines them, and tells you how this compares with the action levels.

Even if you find the total exposure is under the action level, there may still be things to do.  It seems as if you have one or more machines that are very noisy.  It is always worth trying to do something to reduce the noise exposure from such processes, ideally for the operator but if not then at least for everyone else, even if the duration of the exposure is short.

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