Audiometry results

Firstly, how the results are presented, and then below, what the 'categories' of test results mean.

Audiometry results may be presented graphically or as tabular data. Graphically, audiometry results are presented for both ears, in a similar manner to those shown here:

Audiometry results - normal age-related losses

The graph above shows how the audiometry results look, in this case for someone with a perfectly normal reduction in hearing.

Age is a critically important factor when using audiometry to undertake hearing tests. There is a faint red line visible on the audiogram above which simply put is the lower limit of acceptability (this is not the only determining factor but it is a key one) and this changes with the age of the employee.

Analysis of the charts is used as an initial diagnosis, for example:

Audiometry results - damage to one ear

This audiometry chart shows the left ear to be good and above the warning levels while the results for the right ear are heavily reduced. A difference between the two ears such as this is a classic unilateral result for someone who has suffered accidental damage to one ear for example.

Audiometry results - noise induced hearing loss

This chart is a good example of the type of result in which we are interested in workplace audiometry. This chart gives a good indication that the individual is suffering from a degree of noise induced hearing loss, (in this case caused by a feckless studenthood of far too long in noisy nighclubs!). This is classically evidenced by the dip seen at around the 4,000Hz level, followed by a recovery up to 8,000Hz.

In addition to the trends shown by the results, there are other vital components when analysing the audiometry data. Firstly, there is the comparison against the medical history of the person to see if there is a known reason for any observed losses. Secondly the results are compared against any previous audiometry to identify any changes which may have taken place. An example of where this would play a part would be where a subject's result is above the 'warning' levels therefore 'in the clear' but is lower than previous results therefore indicating some loss has taken place in the meantime.

There is a limit to what can be diagnosed with audiometry screening programmes and their main aim is to identify people who may be experiencing a problem. Where the results warrant it these individuals are then referred to their G.P. for further testing to determine the exact cause of the loss. For example, another type of audiometry called 'bone conduction' may show that the loss is due to physical bone damage in the middle ear eliminating noise as a potential cause. This type of testing can only be done under clinical conditions and is not part of a workplace audiometry programme.

It is worth repeating that audiometry is a sensitive test and can and do highlight losses which the individual may be completely unaware of an unable to detect. This means remedial action can be taken before it becomes a problem and often before any loss approaches a level where compensation would be awarded.

Categories of audiometry result

In the workplace, the classification of audiometry results is done according to criteria laid down by Satan's Imp's at the HSE, (Health and Safety Executive). There are four main classifications which you will see on the results, which paraphrased into English are:

Everything is normal for the age of the attendee, i.e. we expect people to lose some hearing with age and Category 1 means their hearing is within the expected range for their years.
There are some losses. It is still with tolerances but is getting low and care is needed to ensure it does not deteriorate further. Think of it as being on the right side of the good/bad dividing line, but peeping through the letterbox looking towards the dark side!
Losses are beyond those which we would expect to see for the individual's age. Unless there is something in their history to explain it or it is a known, managed or previously diagnosed condition, or there is a temporary issue which may have played a part, we would recommended referral for further examination.
This one is only used in Year 2 testing and onwards. When comparing a current result against a previous one (within the last three years), if there has been a sudden reduction in hearing performance a Category 4 would be flagged indicating a rapid change. As with Cat 3, unless there is supporting history a referral would be made.

There is another category which is used alongside this - a 'unilateral' loss. This is where one ear is good and one ear is significantly worse, (see the second graph above). Again, where this is new or there is nothing in the attendee's history to support it a referral is made. From experience, most referrals tend to be as a result of a unilateral loss and the good news for the employer is that unilateral losses are usually not a result of workplace noise. (Most noise affects both ears to the same extent, with some notable exceptions such as shooting, so one ear being worse than the other is probably not a result of loud machinery).

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