Is life too loud?

I think I may be turning into a Grumpy Old Woman.  As a daily user of public transport, particularly buses, I  not infrequently find myself having to move seats to escape from someone who has their iPod (or equivalent) playing so loudly that I find it unpleasant.  I am too frightened to ask the person to turn it down.  I tried this once, very politely, and the young woman yelled at me (she still had the earplugs in) that I should “get into the 21^st century”. Hmmm. 

Mind you, the other day I gently 'toot-tooted' a car in front of me to let him know that he had failed to notice the  light had turned green, and instead of the apologetic wave, I got a finger out the window and a torrent of abuse. 

I do possess an iPod , as they have not yet imposed an age-restriction on their use, and I tried to' join the club' for a while.  I listened to all sorts of interesting things that I had downloaded as podcasts (I have the jargon) from the ABC/BBC.  After a week or two though, I decided that I don't want to travel about in  so much of a microcosm that I can't readily say hello to the bus driver, or eavesdrop on strangers' conversations.  What does concern me though, it the impact that all this exposure to loud sounds will have on people's hearing.

I read recently that today's thirty year old has the hearing of the average 50 year old.  My generation had rock concerts and big speakers (remember them?), but we pretty much  pre-dated the 'personal stereo', aka, the Walkman.  I have never actually enjoyed loud noise, so I used to sneak my earplugs into my ears at the concerts I used to go to, where everyone else was too stoned to notice.  I have never used power tools, a rifle or frequented clubs (formerly called 'discos').  I would have thought that I was entitled to have almost perfect hearing, but I am aware that it is gradually deteriorating.  For me, genes play a big part, but even my low-level chronic noise exposure must have had an impact.

The thing is, spectacles are quite attractive and sometimes even flattering.  The same cannot be said for hearing aids.  The very term conjures up an ugly image of a large piece of flesh coloured plastic attached to a hairy ear (and a grumpy old....) It's hard to imagine a hearing aid ever becoming a fashion accessory.  Granted, my father has a modern German number that is barely visible, and the race is on to produce smaller and even attractive versions of this prosthesis.  I recently saw an American ad featuring a leopard skin printed one.  However, glamorous or otherwise, they are nowhere near as good as the real thing, are a nuisance, run out of batteries and instantly brand you 'old'.  I think I will need bilateral ones in ten years, so I hope those designers are working around the clock.

Hearing is so spectacularly miraculous, yet frighteningly vulnerable. Naturally, we take it completely for granted and assume it will last forever.  Alas it won't. 'Presbycusis', or  'hearing loss of old age' (Gk), tends to occur earliest in the higher frequencies- between 4,000 and 6,000 Herz.  This is like having the treble on the radio turned down .This hearing loss begins to be noticed as people get into their fifties.  Research shows noise  related loss in about 50% of people over 60 and about 65% of people over 70.  Additional environmental exposure adds to this.  I recently did health assessments on several dozen middle aged farmers in country NSW, and their audiograms all showed significant hearing loss in the upper frequencies, much higher than predicted for their age, and they all attributed it to having used power equipment without ear protection in their youth.

Back to those iPods. According to an Australian study, a quarter of iPod wearers on trains are exposing their ears to noise above the recommenced daily levels.  The researchers stopped people on their way to and from work at the main stations in Melbourne and Sydney, measured the volume of their personal listening devices and asked how long they spent listening to them.  They picked these locations as they also have a high level of background noise, so people often listen with the volume turned up to counteract this. They found that about 25% of users had daily noise exposures higher than the recommended level.

But just how much noise is damaging?  That depends on how loud the noise is, and how long it lasts.  The maximum noise allowable in the Australian workplace is 85 decibels, over an eight hour period, five days per week.  Eighty-five dBA is the the level of noise of someone yelling at you from two metres. The music in some Sydney youth- oriented shops has been clocked at 90dBA and above. Leaf blowers and lawnmowers are about 90 dBA, cheering crowds at the footy can peak at 120 dBA.  Movies are generally about 85dBA,  but action scenes can peak at 120 dBA.  Live music concerts, construction sites, aeroplanes taking off: these are all in the 120-130 zone.

It is worth remembering that we have evolved over millions of years against a background of relative silence.  Imagine: There would have been the sound of the wind in the trees, a crackling fire, occasional thunder and lightning, the odd roar of a wild animal, a fight, children laughing.  Even forty years ago, life was much quieter than today.  People had radios, but tended to sit around and listen to them in the evening; no TVs, no washing machines, dishwashers, telephones, clothes driers, less cars, buses and heavy road transport; movies were silent...the list goes on. Sounds pleasant though, does it not?

Because the damage noise does is subtle and cumulative we don't notice it until it has advanced to a critical threshold.  Then, you might start to notice that you are missing parts of the conversation at your table in a restaurant.  If more than one person speaks at once you lose track of the conversation. As the night wears on, you may just tune out. Certain sounds, like 'th', 'fff' and 'shhh', become harder to pick up.  You are aware that you have to ask people to repeat themselves, once, sometimes twice, then it's too embarrassing to ask again. It is very to have a conversation with someone who is hard of hearing; either you or that person tends to give up, and the world becomes very isolating for the deafer person.  A patient told me a sad story last week of her father who had been slowly dementing for years.  In his last two years he really stopped making a lot of sense, which they attributed to the dementing process.  It was only a few months before he died that they discovered he had actually been going deaf, magnifying his isolation.

Sounds arrive at the ear as waves, which the eardrum, or tympanic membrane, converts into energy that rattles the three delicate little bones of the middle ear.  This results in a pressure change in the cochlea, which is the coiled, fluid filled tube at the heart of the ear. It has the volume of a small marble. This in turn translates the energy into chemical and nerve signals  that are  then sent to the brain.   The cochlear, which has about the volume  of a small marble, is lined with tiny 'hair cells' arranged in a zig-zag pattern.  There are relatively few of these cells, only about 16,000 per ear, which is less than the number of cells on a flake of dead skin.   Interestingly, the cochlear is adult sized at birth, which means cochlear implants are possible in newborns, as long as they have a cochlea and a cochlear nerve.  These are now being done in Sydney in 3 month old babies. Different sound frequencies affect different types of hair cells.  They are so highly evolved that they enable us to detect the direction a sound is coming from and the difference in time between two sounds separated my a few degrees in space and milliseconds in time.

Hair cells  that are damaged by infection, drugs, aging or excessive AC/DC exposure are lost for good. Thus, the ear  system is vulnerable.  The only animal that we know about that has cochlear cells which regenerate are some species of lizards, so these are being studied intensively to see if we can somehow turn on this self- repair mechanism  in humans. Hair cells are quite unique.   In a quiet environment the hair cells in normal humans are turned up to amplify the softer sounds , in fact turned up so high that they themselves generate a faint but constant tone of sound. If you were to place a small microphone to the ear of a sleeping person you may even be able to hear them at work. In a loud environment, they turn themselves down. Our brain filters out the noise of our hair cells, in the same way that it filters out the noise from our own singing or speaking.  The brain halts the auditory neurons so that we don't get swamped by all this, and also to allow us to suppress the background of auditory stimuli.  Think of all the buzzing, banging, humming, thumping, whistling noises that are part of our morning routine.  Thankfully we are able to only 'hear' what interests, so long as we still can hear. 

It's unlikely we will find a way of repairing cochlear hair cells in our lifetime, or even in those of our children.  So the best advice can only be to protect our hearing tenaciously, carry a pair of foam earplugs in our pocket or bag, and to go softly....