Check out the link below– it’s
the same discussion on the IOSH chatroom which I found very interesting
http://www.iosh.co.uk/index.cfm?go=discussion.view&forum=1&thread=29560
Karen
Karen Coomer, MSc, BSc
(Hons), OHND, RGN, CMIOSH, MISMA
Occupational Health
Specialist
KC Business Health Ltd
Tel: 01904 440323
E-mail: [log in to unmask]
Web: www.kcbusinesshealth.co.uk
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From:
[log in to unmask] [mailto:[log in to unmask]] On Behalf Of Eric Greig
Sent: 09 January 2008 15:34
To: [log in to unmask]
Subject: Re: [OCC-HEALTH] Ambient
noise levels during audiometry
There seems to be some confusion here.
The H&SE publication "Contolling
noise at work" published in 2005, refers to EN 26189:1991 for guidance on
how quiet the environment should be before test results are affected.
What matters of course is what the ear
hears, and the ear is protected from environmental noise by the earphone
cushion plus perhaps an audiocup, plus perhaps a booth.
Table 2, provided in EN 26189 (see
below), gives guidance on the maximum level (of octive band sound
pressure) allowed in the test environment near to the head, assuming:-
1) the Beyer DT48 or TDH39 earphone
fitted with the MX 41/AR cushions are used and
2) you don't want to measure accurately
thresholds below 0dB
If you add audiocups or a booth then you
can allow higher levels of background noise, but if you are dealing with new
starts and want to accurately measure baseline audiograms, you will want to
test and look for thresholds well below 0 dB, and will therefore need a much
better test environment.
An accurate assessment of what
constitutes a valid test environment therefore needs to take into account:-
1) the background noise measured in 1/3
octave band frequencies
2) the background noise supression
provided by earphone cushion, audiocup and booth
3) the lowest level you need to measure
to
The background noise at each of the
relevant frequencies, can be determined with a good sound level meter.
The supplier of your
equipment should be able to give you a table of attenuation values
provided by the setup you have (earphone cushion, audiocup and booth etc).
You should probably assume that you want
to measure to at least -15 dB to cover every situation which might arise.
Please remember that the table below is
only relevant under the very restricted conditions detailed above.
Regards
Eric Greig
Freq |
|
Lmax |
|
|
|
500 |
|
18 |
1000 |
|
20 |
2000 |
|
27 |
4000 |
|
38 |
8000 |
|
36 |
From:-
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