Archive for March, 2008
March 29, 2008
For past blogs I have always tried to find some sort of quirky, eye catching title. Once again though ear moulds remain unglamorous, unloved, unappreciated and strictly utilitarian. These days though they are quite high tech and vital to successful operation of modern air conduction aids, particularly at the high power end of the range. Individually fitted moulds are a fairly recent innovation, being developed in the mid 1900’s by adopting dental methods and materials, both for impression taking and construction. They are a far cry from the early injection moulded plastic, rubber tipped, cones that came in “small, medium & large” only. These had a poor seal, worked lose continuously, and fell out at the most inconvenient moments.
Modern moulds have to be a good fit into the ear canal and remain in position under difficult circumstances. The ear canal is very close indeed to the jaw’s “hinge” mechanism and is continuously flexed by the jaw and its muscles during speech and eating. The outer ear and canal together form a complex three dimensional shape, and making a nearly exact matching shape that can be inserted and removed relatively easily is challenging. All ears are different and insertion can be difficult, particularly with a new or especially deep mould. The action is a bit like a bayonet light bulb fitting, but with four stages instead of the bulb’s simple two stage – push then turn.
A poorly designed mould (or one that is not quite inserted correctly) can quickly cause extremely painful pressure sores. These form by the same mechanism as bed sores and are caused by continuous pressure at one localised point. They can be initiated inadvertently by many very minor changes, but are easily corrected once the cause is found.
With ‘behind the ear instruments’ amplified sound is channelled through the solid mould by a replaceable plastic tube. This passes through a duct drilled during the later stages of production. ‘In the ear’ aids are more complex, the moulds being produced as a hollow shell into which the entire instrument is assembled.
One very well known drawback of hearing aids is feedback. Also called ‘whistling’ and a host of other descriptive terms. Another very similar effect used to be the ‘howling’ common with poorly set up public address systems and microphones at local ‘hops’ etc. It is caused when amplified sound from a speaker has a relatively direct path back to the microphone. This causes some sensitive frequencies to be amplified even more, and round and round they go!
With hearing aids the microphone and speaker are, of necessity, extremely close together and feedback becomes increasingly difficult to avoid as the level of amplification is raised. Digital aids are much better at controlling this effect than the old analogues but a well fitted mould is still a major requirement for good operation. It must seal off any air path from the sound output to the ear drum, back to the microphone. Even with a good mould, feedback is still possible if anything (or anybody!) is placed very close to the aid. This is due to a different, sound reflection, mechanism. Even when part prepared, you can bet that an aid will always start to scream at the most inconvenient time when working in a very awkward position. Under a car bonnet, or wiring under the floor are obvious examples that come to mind immediately. The reader can perhaps imagine others.
The seal of the mould in the ear is so important, yet so difficult due to movement of the jaw. Moulds made from hybrid materials are now common in an attempt to combine the rigidity, required for good location, with flexibility for a good seal. In this case the bulk of the mould is rigid but with the innermost tip being a more rubbery formulation.
Moulds sealing as well as this can lead to their own problems. They don’t cause infections but they do constitute an unnatural environment in the ear which can incubate any existing problems. Remember many people, such a myself, are wearing aids due to damage caused by chronic infection effects. Condensation can also be a problem with behind the ear units, as the sound tube acts as a very efficient condenser particularly in cold weather. Droplets of condensation blocking the tube can cause sudden loss of hearing and cannot be removed without removing the aid. Also a drop of condensation running back into the ear is harmless but intensely irritating.
For these reasons ‘vented’ moulds are available for people who have a persistent condensation problem. After all I have said above about feedback and a good seal, I have no idea how this can be accommodated. I can only assume that the vent channel follows an indirect path and somehow emerges pointing away from the microphone area.
Pretty clever things really, all being considered.
March 17, 2008
This blog owes its existence to my starting formal lip reading classes, closely followed by a very basic sales training program. I have exaggerated things slightly for emphasis (blogger’s licence ?) but I believe the concepts are as sound as any other aspect of popular psychology. While hearing impaired people are amongst their regular friends and acquaintances, these people make allowances for any possible perceived “rudeness”. The effects discussed only really come seriously into play when meeting strangers, particularly if there are important things at stake. I will try to avoid ‘he’ and ’she’, as in most instances the effects apply independently of the gender of both the ‘reader’ and the ’subject’.
A good way of making someone feel really uncomfortable during a conversation is to spend a lot of time looking at their face, but never making eye contact. The middle of the forehead and the throat area are particularly effective for this. The mouth is obviously very potent as well. It has the added complication that many women will worry about some imagined make-up or facial blemish, and will either start to cover their mouth or not relax until they have checked in a mirror.
As the mouth is very close to the eyes, it is very easy to try to compensate for this by making frequent eye contact. Unfortunately this is a strong sign of at least good friendship, possibly even attraction or affection. This is perhaps not always welcomed by strangers, so the answer is to look away as often as possible to try to maintain only normal levels of eye contact. The problem can be heightened by a tendency to place yourself nearer to the subject than normal, to hear better. This again is only really tolerated by a subject if the person is a close friend (note the significant adjective). In the case of a stranger it constitutes at least over familiarity, perhaps even aggression. We must always read the person, as well as the lips, and try to find some mutually acceptable compromise.
We are told that the best position for lip reading is with reader and subject facing each other. Yet “face to face” is quite rightly synonymous with antagonism. If coupled with invasion of personal space it is aggressive, and pictures of boxers “facing off” at weigh-in are common before a big fight. Very close, face to face and trying to “stare the opponent down”. Sound familiar? Ninety degrees between the bodies is a far more useful working alignment.
The same applies to seating at table. Pub lunches are a popular low key form of entertaining customers, yet can be very difficult to stage. The recommended alignment would be both sitting on the same side of a longish table. Under normal circumstances that puts you both tactically “on the same side” as well as literally. In my case though the tendency would be to sit too close to the subject, spend a lot of the time with my head noticeably turned to gaze at the subject’s face and making too much eye contact. Not good! Again ninety degrees on a smaller square table is far preferable. Lighting continues to be difficult, the preferred situation for reading again being very uncomfortable for the subject, with a good light shining on their face (into their eyes?). There are other informal protocols about seating customers comfortably, which can very often run contrary to reading requirements. On several occasions I have apologised to important contacts if I couldn’t discretely manipulate a suitable seating arrangement. I have never found explaining why I wanted to change the positioning to be a drawback, especially when coupled with “because I want to be as sure as possible of what you are saying”
Acknowledgement of authority can be a major problem, particularly with eastern cultures. I have been shown respect by a person lowering both their head and voice when speaking to me. Unfortunate. I far prefer the approach often shown by ex-military personnel, rarely any need for guesswork there. The reverse problem arises when a reader talks with a superior. Unexplained reading would certainly be considered very disrespectful in some cultures. Even in European ones, high ups can be uncomfortable with it, perhaps interpreting it as over familiarity by a subordinate.
One last point at the end of a long blog. Readers would do well to consider what they themselves look like while they are reading. I find some situations very difficult and tiring, and professional colleagues have warned me that my natural expression under these conditions is somewhere between a frown and a scowl. Again not good social practise.
As a summary then. If I had an appointment with a perfect stranger, and I wanted to ensure my best conversation conditions, as regards accurate exchange of information. The subject would have their face well illuminated and I would be directly facing, looking at the lips only. Our faces would be unusually close together and I would be scowling slightly.
If that didn’t make us instant friends, I suppose I could always try the thumb screws. 
March 9, 2008
This would all be rather mundane apart from the fact that I am doing these things for the first time with a titanium screw in my head, and a recent skin graft.
I went to the barbers on Tuesday (4th) and received a completely normal haircut. He seemed absolutely un-phased by the abutment and graft, working at his usual speed and not seeming to make any allowances for them at all. He certainly didn’t make contact with the abutment. My daughter, on the other hand, has inadvertently tapped the mounting with scissors when trimming the hair around it. The result was unexpectedly loud without an aid, and definitely high specification metal against high specification metal. If that is too much engineer speak, the nearest ordinary thing I can recall would be playing marbles with ball bearings as a boy. To me, a very sharp “click” sound with lots of reverberating high frequencies. Very encouraging.
Before the haircut I had been to the gym for my third BodyPump session, after an absence of 6 weeks. There was no effect on the graft. In fact after the first session, the graft was about the only bit of my anatomy that didn’t hurt. It was a major feat of willpower to force my aching body back for the second session two days later, but it’s no real problem now.
I have also finally removed the Christmas lights from the damson tree. These have been ‘awaiting my attention’ after being abandoned to their fate in the very wet and windy weather early in the New Year. At about 40 years old it is a mature tree, some 15 feet tall with “the canopy being a dense growth of stiff, brittle twigs”. It can remove most normal headgear and glasses with ease, and inflicts multiple minor stabs and scratches on any unprotected skin. A redoubtable opponent when tackled from underneath using of a rather insecure ladder. Definitely another job for the silly hat with ear flaps, this time with the chin strap tightly fastened as well.
On a more serious note. I was approached by a stranger in Tesco who very politely asked if I would mind talking with him about the abutment. He was asking on behalf of a relative who was being recommended to have the procedure as a follow up to much more serious medical treatment. Once again I feel that, all in all, I have had it comparatively easy.
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