Deafening our children

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Have you ever wondered just why Thai ladies cannot talk quietly together?  Women’s conversational Thai is a language shouted at full volume, with everyone talking at the same time.  For the western male this is something of a (noisy) mystery.  However, I have unearthed the secret, and it isn’t a pretty tale, I will tell you now.

What prompted this week’s column was my accidentally stumbling into the 2011 Aerobics championship for schools being held in one of our shopping malls.  Whilst it was good to see so many of the schools having an aerobics group present, showing all kinds of physical skills, this was done to music emanating from a bank of huge boom boxes, with MCs shouting into their microphones, to be amplified to the same levels.

When I was practicing as an Occupational Health Physician, we would monitor the noise levels in factories, which by the very nature of the type of work being done, were quite noisy.  The upper limit was 90 dB for eight hours.  The local shopping mall was nowhere near 90 dB, but I would suggest it was at 120 dB at least.

Now groups such as OSHA (Occupational Safety and Health Administration) in the USA have been able to produce world standards for noise exposure.  90 dB for eight hours, 105 dB for one hour and 15 minutes or less for 115 dB.  Anything over that and irreversible changes occur in your ability to hear.  That’s for adults – children are more sensitive to noise.

The children in the shopping mall were there for around two hours.  About 10 minutes on stage and an hour limbering up and probably another hour watching the other schools.  That is far greater than the 15 minutes at 115 dB, and let me assure you, it was much louder than that.  It was at the threshold of pain.

To give you some examples of noise levels:

Normal home or office background is around 40-60 dB.

Normal speaking voice is 65-70 dB.

Orchestral climax at 105 dB.

Live Rock music: 120 dB+.

Pain Threshold: 120-130 dB.

The ear is made up of three different parts, including the outer ear which is the part you can see.  Its shape helps to collect sound waves.  A tube, called the external ear canal, leads inward to the eardrum.

The middle ear is separated from the outer ear by the eardrum.  The middle ear contains three tiny bones called the malleus (hammer bone), the incus (anvil bone) and the stapes (stirrup bone).  These bones amplify the movement of the eardrum produced by sound waves making the drum move in and out.  The Eustachian tube connects the middle ear to the back of the throat and helps to equalize air pressure.

The inner ear is where the sound waves are picked up by a tiny spiral-shaped organ called the cochlear.  Hairs on the cochlear sense the vibrations and pass the message as electrical impulses to the brain via the cochlear nerve.  The whole system is very sensitive.

There is no doubt that the young ears would be damaged by the noise exposure they suffered last week.  If they were very lucky, it would only be a temporary form of deafness (called a temporary threshold shift), but enough repeated exposures will result in permanent degrees of deafness.

Now think of any outdoor party or concert you have been to in this country and cringe at the memory of the loudness of the music.  One hour at 105 dB is the safe limit.  That limit would have been exceeded both in time and in volume (dB’s).

It is improper for me to be too sweeping with statements, but if your Thai wife has been to enough stage shows, concerts and outdoor karaoke, she will have permanent hearing damage by this stage.  So will her friends.  And so they have to shout louder.  And you go to the pub for a bit of piece and quiet!

This also goes a long way towards explaining why the local populace does not hear phones ringing, and why the girl in the next office has her mobile phone ring tone set on maximum.  And I know she has an incoming call before she does!