Expectations of audiometry

With workplace audiometry, the best way to think of it is as an initial sorting process, looking to identify who is OK, who has a bit of a loss and who has a problem, which may or may not potentially be noise related. Those with a problem can then be focused on, usually by referring them to their G.P., and that's pretty much the aim of it.

To be clear on this - no workplace audiometry testing can turn around and say to you "this person has noise induced hearing loss" or "this is where noise has damaged your hearing". No matter what any provider may tell you, all screening can do is say that a person has a problem or not, and based on the attendee's personal history there is then a chance it may be noise related or it may not, and that is why further investigation is needed by a G.P. and often an ENT specialist.

The wording in that sentence above was very careful as well - in the next to last line it says "may be noise related", not that the loss may be "work related". That's an important semantic difference as all noise has the same impact on hearing, irrespective of source. So whether it is a bass drum or an angle grinder, or a nightclub or an air gun, it impacts on the same part of a person's hearing, therefore a loss at say the 6kHz frequency in both ears may indicate that noise has caused a loss, but it is impossible to say which noise it was. The impact on hearing from someone playing a flute in an orchestra is the same as someone standing next to an chop saw.

This is important as the losses from noise are permanent and a few years as a disreputable youth may have given someone a decent loss in hearing in their 20s, which is still present as a quiet employee in their 40s who considers a wild weekend to be watching Midsomer Murders over a glass of wine. The nightclub 20 years ago gives the same pattern of loss as the bottling plant they are now working on. This is why the history is so important.

There is also a complication that in a recent study, 37% of people in the group who had no history of noise exposure at all still had that same drop at the 6kHz level, meaning that it is a perfectly normal pattern of hearing and not definitive of noise losses. To be clear - this contradicts some of the statements made by the HSE who do say a loss at 6kHz is definitive for noise induced hearing loss, sadly it isn't. (It's not the HSE's fault, sadly things aren't often black an white in this subject area and also the research referenced here is newer than the information published in L108).

The skill comes in from the technician conducting the audiometry - the result obtained from the test itself is only one of the criteria the technician should take into account, with an equal weight being given to the reported health history from the patient, how the ear looks when the technician looked down it with the otoscope, any comments they made in the conversation and also how confident and precisely they responded to the audiometry test tones. If any technician says 'someone who scores a Category 3 result should always be referred to their G.P.' then they should be told to go away in no uncertain terms - automatic referral is frankly a sign the technician doesn't understand the subject. This also goes back to the question of chucking someone in-house on a one or two day audiometry course and then letting them loose to do the testing, this often is not good enough and tends to give the 'I refer all Category 3 cases' approach, which is of extremely limited use to the employer and employee alike.

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