What do the hearing test result categories mean?

Part of a noise assessment is to determine which people need to be included in a health surveillance programme which is an ongoing series of hearing tests for people exposed to high noise levels.

A common abbreviation you will see is ‘NIHL’, this means ‘noise induced hearing loss’, more on that in a sec.

The hearing tests are categories according to criteria set out by the HSE in L108, and are:

Hearing test categories as defined in the HSE's L108.

What that means in English…

NIHL

Having an identification of NIHL, noise induced hearing loss, doesn’t mean it has been caused by work, it means some hearing damage caused by possible high noise exposures. That could be work, but as noise damage is permanent it could have been regular time in nightclubs 20 years ago, or a lot a headphone use, etc.

In the old days it was called Industrial Deafness but the ‘industrial’ was dropped as it implies a cause, but as all noise has the same impact on hearing, whether it is a loud machine or music, then identifying possible noise damage cannot confirm a cause.

NIHL is common, very common. In a sample I did of over 5,000 hearing test results, around 67% had some level of NIHL. If you are told you have some noise damage that doesn’t mean you are deaf or that your hearing is weak, or even that it is weaker than it should be for your age, it is just a statement that there is some damage, probably caused by noise exposure, and the majority of people show that pattern.

Category 1

Someone with normal hearing for their age. It doesn’t mean the hearing is perfect as hearing is supposed to get worse with age. Someone who is 25 should indeed have nigh-on perfect hearing to be Category 1, while someone who is 55 could have some fairly chunky reductions but it is still normal for their age.

That means a slightly older person may start to notice some occasions when they struggle to hear clearly but they could also still be Category 1 as their hearing is not supposed to be as good as it was.

To be Category 1 there must be no signs of possible noise induced hearing loss (NIHL).

Category 2

This is where it starts to get a little trickier as Category 2 can be either:

• If it is their first hearing test, they could be someone who has some reductions in their hearing which are getting towards the lower end of what is acceptable for their age, but it is still a pass. No NIHL can be present.

• Or if their second or subsequent test, it can be someone who has good or even excellent hearing overall, but there are also some signs of noise damage present, but the testing is showing it to be stable and not deteriorating.

From experience, for people who have had multiple hearing tests, the majority now fall into Category 2 because they have perfectly fine hearing overall but there are some signs of noise damage, usually from being a more exuberant youth. In effect it is normal for a lot of people who have lived a little.

Category 3

There are three ways to end up as Category 3:

• Someone who has hearing which is weaker overall than it should be for their age.

• Someone who has otherwise good or even very good hearing, but they have signs of noise damage present which have not been identified before as this is their first hearing test with their employer.

  If it is a first identification of the possible noise damage the HSE say they have to be Category 3 no matter how good their hearing overall.

  (Frankly this is mad - I have seen many many people who have hearing which is superb but they have a bit of NIHL from some clubbing decades ago, but as it is their first test they have to be Category 3).

• They have signs of noise damage which is getting worse compared to previous years.

Category 4

The HSE were really not helpful with their naming here as Category 4 is different to the others. The others are all a level of hearing against expectation for their age or where noise damage is present, but Category 4 means they have a significant deterioration compared to previous years. Category 4 is therefore a rate of change, not a level of hearing.

Someone can be Category 4 but still have excellent hearing, just that it was even better last time.

Unilateral hearing loss

If you have had a hearing test you may also see a result of ‘unilateral’, usually something like ‘Category 2u’. Unilateral means the hearing in one ear is weaker than the other.

Hearing should be similar in both ears so having one lower than the other is a possible sign of a problem. The most common causes are simply a blocked ear canal or an infection in one ear.

From a noise perspective, there are some noises which can hit one ear more than another and the common ones are shooting and being a DJ. In the old pre-aircon days it was also common for van and HGV drivers to have one ear showing more losses than the other from spending hours every day driving with the window open, giving a significant noise exposure to one ear, but that’s less common now.

It is pretty uncommon for occupational noise to cause NIHL in one ear only and therefore cause a unilateral classification, purely as most industrial noise hits both ears pretty much equally.