 Audiometry home
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Audiometry routine & reports
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Types of hearing loss
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Audiometry Q & A
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Noise surveys / assessment
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Noise training
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About hsmc
testing unit waiting area,
acoustic linings visible
Audiometry booth in
a mobile unit
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Types of hearing loss
Audiometry in the workplace is undertaken to try and
identify any hearing losses which are taking place due to noise exposure,
but why is it such a big deal?
There are two effects of high noise exposure - the hearing loss itself
and Tinnitus.
Tinnitus
This is experienced by many people, most often as a temporary ringing,
whistling or buzzing in the ear, (note: if the noise in the ear is more
akin to a voice saying "The Pope is an alien who has come to steal all our
pizza" this is probably not tinnitus, but does make you quite scary...). At low levels it is often
ignored but it can become permanent and have a huge impact on the life
of the sufferer.
Temporary tinnitus arising from colds, recent flying, etc. is perfectly normal and fades away again but tinnitus arising by noise is a more serious matter. During
the day this is often swamped by other noises but at night it can keep
sufferers awake which, as you may imagine, going on for month after month
and year after year has enormous impacts on their physical and mental
health. This is not helped that tiredness is also known to cause tinnitus, and so a vicious cycle can begin.
Hearing Loss
The second potential effect is a reduction in the individual's ability
to hear, with the greatest losses unfortunately being suffered at the key frequencies used to give meaning and clarity by the human voice. The loss is caused by the
cells in the ear which detect noise being damaged and ceasing to work.
The loss is permanent and cannot be reversed - the cells will not grow
back or recover.
Other causes of hearing loss
In addition to the losses of hearing through noise exposure there are many other factors which may cause a loss in hearing ability which is evident during the audiometry, including:
- Physical impact to the head from falls, accidents, etc. (We have met one chap on our audiometry travels who had good hearing but then suffered a heavy blow to the head leaving him unable to hear noises at 100dB in both ears and profoundly deaf).
- Common childhood diseases such as mumps in some cases can impact on hearing.
- Other diseases such as Meningitis may harm hearing as a side effect.
- Diseases of the ear specifically such as glue ear.
- Some drugs affect hearing including medical prescriptions such as some blood pressure treatments but also more common chemical compounds such as nicotine, caffeine and ibuprofen which all carry a very low but present risk. A smoker with a headache, a 10-a-day coffee habit and high blood pressure is like a red flag to us!
- Physical damage to the ear such as a burst ear drum or one which has been subject to surgery.
- And last but not least - the most common - as people start knocking on a bit their hearing naturally gets worse. The following are rough and ready charts of hearing loss in ten year increments. These show the lower limits of what would be acceptable hearing with increasing age - ideally hearing would be better than this. (These are the levels beyond which we would refer an idividual if too many results were dropping below the lines).
As a very rough guide at the age of 65 a man may show a loss of up to 70dB at the 4KHz frequency, while a woman may have lost up 58dB at the same point.
This loss in itself is significant and if a younger person was to suddenly go from their normal hearing to the ability of a 65 year old the losses would sound profound.
The basic principle of workplace audiometry is that we use the hearing tests to identify losses before they become a problem and avoid adding further reductions in hearing due to noise to the ageing process.
How this relates to the audiometry reports you will receive
The individual 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:
The graph above shows how the audiometry results look, in this case
for someone with a perfectly normal reduction in hearing.
The age-factor is taken into account by the 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.
The following audiometry chart shows the left ear to be good and above
the age-related warning levels however the results for the right ear are heavily reduced. A difference between the two ears such as this is a classic result
for someone who has suffered accidental damage to one ear for example.
The final one below is the one we are interested in, particularly in workplace audiometry. This chart gives a good
indication that the individual is suffering from a degree of noise induced
hearing loss. This is classically evidenced by the dip seen at around
the 4,000Hz level, followed by a recovery up to 8,000Hz.
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