the noise exposure. Most international regulations for noise exposure at work state that the loudest noise someone should be exposed to for an 8-hour working day is 85dB - roughly equivalent to a blender, or a milling machine. Now, as we saw before, a 88dB sound is twice as intense as a 85dB sound, so it follows that the maximum exposure duration should be half as much, so 4 hours. This rule of halving the maximum exposure duration for every 3dB increase (so doubling) in sound intensity is true for noises up to around 110-120dB. Above this, even a very short exposure time can be damaging. A WDEOHRIPD[LPXPH[SRVXUHWLPHIRUDUDQJHRIQRLVHLQWHQVLWLHV EHIRUHGDPDJHPD\RFFXU
Noise intensity (dB)
Maximum unprotected exposure*
Typical example
85 88 91 94 97
8 hours 4 hours 2 hours 1 hour
blender, milling machine
forklift truck Tube train lawnmower
30 minutes 15 minutes 7½ minutes 3¾ minutes 112 seconds 66 seconds 33 seconds
LQGXVWULDOÀUHDODUP
100 103 106 109 112 115
bulldozer, handheld drill mp3 player at full volume
motorbike
crying baby, jackhammer
live rock band
emergency vehicle siren
* before damage may occur
Whilst the BTA makes every attempt to ensure the accuracy and reliability of this information, it is not a substitute for medical advice. You should always see your GP/medical professional. Measuring the duration of exposure is quite easy. However, it is hard to measure noise intensity without specialist equipment, so how do you recognise whether noise is loud enough to be damaging?
Made with FlippingBook Ebook Creator