Ear We Go

January 25, 2008

Well, I now have the mounting in place but won’t actually be allowed to see it for 10 days or so. It is swathed in three layers of dressings which are discarded or replaced over this time, until the final denouement. I opted for a local anaesthetic for the procedure. I have nothing against generals but don’t see any point in taking any extra risk at my age, however slight. During the operation I alternated sharply between the engineering instinct of trying to deduce exactly what the surgeon was doing – and the human instinct of worrying that, whatever he was doing, he was doing it to my head !! Definitely not for the faint hearted.

This is intended to be the last blog with a predominantly technical slant, explaining why this particular system should be very beneficial to myself. Hopefully visitors will have realised from previous postings that it is not going to be appropriate for everyone. If you are interested, by all means ask your audiologist’s opinion of the system. I really wouldn’t recommend specifically ‘demanding’ any given procedure or device from the service.

The charts below show my initial assessment in October 2007 which lead to this system being recommended. Measurement is now a computerised process, using modern equipment. Please bear in mind, if you want to look back to the 94 chart ;-

1. Audiometry is not an exact science.
2. At this level, hearing can change on an almost daily basis depending on infection, blockages, tinnitus levels etc.

The audiologists would probably say that the two ears are about the same for all practical purposes. I personally regard my left ear as the ‘good’ one, and the one I would least like to do without. You will see that (by my standards) it is quite good around 500-1k Hz, general speech frequencies. I do think of it as a ‘flat’ sound though. I consider my right to give a generally ‘brighter’ sound, possibly due to it being slightly better at the higher frequencies. Discounting the basic stereo advantage of wearing two aids, I am uncomfortable without either one of them. Let’s face it, I need all the clues I can get to work out what is being said.

The interesting thing about these charts is the upper line shown for the right ear, though it essentially applies to both ears. It is measured making the test not via the source / air / eardrum path, but from a source pressed against the bone behind the ear. This is called bone conduction and effectively bypasses the eardrum and middle ear to transmit the sound directly to the inner ear. Readers will appreciate from this line just how much advantage the bone anchor system offers someone in my position. (About 50 times louder) The normal practice is to fit to one side only as bone conduction is particularly good, with only a 5dB loss across the scull giving hearing in both ears. This level of transmission loss is detectable though and bilateral fittings for full stereo effect are not unknown.

In my case here are two further advantages of the system. Because most of the interference noted under 2. above occurs in the middle ear, it is minimised by using bone conduction. So a less variable level of hearing should result. The other quite important thing is that my ears will no longer be sealed off from the air for 16+ hours per day. Perforated eardrums are particularly prone to infection at the best of times. Keeping them moist, warm and unventilated is a very good way to promote continuous infection and inflict further damage. ( a tight seal in the ear canal is essential for high powered aids)

On the whole, as I said before – ‘a no brainer’ decision, for me at least.

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Apart from dressing changes and stitch removal, nothing much happens now for about 3 months as regards the bone anchored aid project. I will continue to post though about every 10/14 days or so, on more general experiences and aspects of hearing impairment.

Posted by kevin

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Just a Tiny Bit of Physics

January 19, 2008

At my last hearing assessment it was patiently explained to me by the youthful, but extremely pleasant and knowledgeable, technician that audiology is not an exact science. It involves the physics of sound, of course, but also a lot of physiology, brain function and to some extent psychology.

Even so, they use graphs to record and typify hearing loss and these use technical terms. We must have some understanding of these terms to go any further. The concept of decibels (dB) however is very complex and the properties are interpreted or emphasised in different ways by different technologies. They have some very surprising characteristics, and we will perhaps approach these later but only if absolutely necessary.

This is an audiogram from my records dated July 1994. The figures across the top are sound frequencies (Hz) ranging from 125, a deep hum, to 8000 (8k) a high pitched whistle. The healthy human ear is capable of an even greater range but the important usage range, particularly for speech is 500 to 2k. As an example of these, the lower frequencies cover the tones (not loudness) of ‘bass’ musical instruments. Also the ‘oo’ sound in “who” and several consonants said ‘with voice’ (a bit difficult that, but see next paragraph)

The higher frequencies are squeaks, hisses and whistles. Typically birdsong but, extremely important in speech, s, f and t etc. which are produced mainly by blowing air in various ways between the tongue and teeth. A pure ’s’ for instance is just a hiss of air. If you try to say it loudly by using some voice behind it, it becomes a ‘z’ similarly a loud ‘t’ becomes a ‘d’, and ‘f’ a ‘v’. (Try it. Just shouting often confuses things. ) Other obvious sibilants are ‘h’ and ‘th’.

The figures down the left side are the hearing loss in dB, the zero line almost at the top representing the hearing capability of a normal 20 year old male (It’s probably defined in a more scientific manner than that now, but not much different in concept).

The audiogram shows the patient’s hearing loss for each frequency and for each ear. The left plotted as ‘X’ and the right as ‘O’. The graph shows for instance that at a frequency of 250Hz, my left has a loss of 75 dB, and the right 80dB. At 2k Hz the loss is 80dB in the left and 65dB in the right.

In general you would say that I had a fairly even loss of 75dB across the board but with both ears weakening above 2k, particularly the left.

Because of the general uncertainty of the base standard and procedures etc. the following loose classifications could be said to apply:-


The figures in the last column may look a little strange. That’s the wonder of decibels. You would be advised just to accept the figures as fact for the current exercise. If you want more advanced stuff, a web search for ‘decibel’ will provide enough material to keep anyone confused for days.

What I hope this all demonstrates is that hearing loss is very personal and the effect depends very much on where, as well as how much, the loss is. Things could also be interpreted differently depending on the patient’s individual circumstances.

I knew my ears were badly and permanently damaged after a measles-mastoid infection at the age of about three. I saw a specialist in Oldham about 1960. His verdict was that I did have a hearing loss and that my hearing would deteriorate a lot faster than normal with age. I didn’t need an aid currently but would probably need one at about the age of 30. Two years later I was told I would benefit from an aid NOW and probably would have in the previous few years as well.

My hearing hadn’t changed much in the time, and I don’t think either opinion was basically wrong. It was merely the difference in my own aspirations. In the first instance I was a grammar school kid in his home town with a mild loss but some lip reading skills. In the second, the same person but struggling with a demanding degree at a top London engineering faculty.

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Like a Hole in the Head ?

January 12, 2008

Later this month, if all goes well, I shall spend a couple of hours as an outpatient at the local hospital. They will peel back a circle of skin, about the size of a 2p piece, behind one of my ears. A small hole will then be drilled part way into my scull and a titanium stud screwed in. The skin will then be replaced after being permanently epilated. When the stud has had time to bed in firmly, I will be able to attach a small grey box (2.5 x 1.75 x 1.0 cm) by a sort of press-stud arrangement.

The reason for all this is that, at the end of it all, I should be able to hear better. I get on OK’sh with my current hearing aids, so you might assume that I would think twice about what could be considered a small but significant disfigurement. Actually the decision was, what the Americans used to call, “a no brainer”. The offer was accepted as soon as it was made, without the proposed time for consideration or meetings with existing users.

I have worn a hearing aid since 1962/3 and the idea of having a small box screwed to my head at the age of 64 is nowhere near as embarrassing as it was for a 19 year old student using a body worn aid in central London. Mod gear and Carnaby Street just didn’t cater for such fashion accessories. If I was going to lead anything like a normal life, though, with a professional career, I had to be able to understand with considerable accuracy what others were saying.

In a way it was very lucky things happened when they did. I was quite determined at the time not to try to hide my deafness. I knew that it was not realistically possible in my situation. I had known several ’shy’ aid users at that point and one particular ‘up front’ user. I was determined to be one of the latter. To be honest, considering my friends at the time, trying to deny the situation was just not a valid option. There was a fair amount of semi-professional interest amongst the group, as well as personal support and understanding. In a ladish sort of way that is! If you are going to go bionic (a word not invented at the time) a group of engineers, medics, one physiologist and a psychologist is as good a place as any.

I have started this blog in the continuing spirit of the ‘up front’ hearing aid user. I intend to post every so often about this new type of hearing aid, why it has been recommended for my situation and my experiences with hearing impairment in general.

Deafness is at last starting to be widely recognised as being no different to eyesight problems. With the age of the general readership of this site being what it is, you can be assured that hearing difficulties are coming soon to a person near you. It’s not the end of the world and if people can benefit in any way from sharing my views and experience, I’m quite willing to write about it..

Posted by kevin

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