I am looking into calibrating Audiometers in a workshop environment and/or even out in the field (if possible). Does anyone calibrate their own Audiometers out there and what test equipment would I need.

F-storm
If you have the budget, I will suggest you get in contact with Larson Davis & Quest to get your calibration kit together.
Bear in mind it is quite expensive to get this going.

You will also have to contact numerous OEM's of actual audiometers (tremetrics, ovation, etc...) for the cal codes of the respective devices and on top of that you will have to contact the multitude of patient management software companies (AMS, Symphony etc...) in the market to get their access details so you can update their systems with new calibration dates.

believe me....
you are entering a minefield

but if you believe in Occ Health and you persevere you will triumph....

Is Williams & Co. branching out into calibration of audiometers as well, then?

Adrian Whatmore at Taunton has always been "the man" when it comes to audiometers. Unfortunately, we don't see Adrian on here (although I have a suspicion that he may be a lurker). However, another of the fine men of Somerset does get on here a fair bit, so perhaps he could pass on any messages you might have.

Meanwhile, yes you obviously need the test equipment, but you will also need a proper place to work in as well (something along the lines of a audiometric cabin - as often found in hospitals - is what I would think in terms of). Audiometers can be checked in the field, but true calibration has always been a "base workshop" undertaking.

Geoff......

I hope one day I might convince you to pack a bag and work for bioclinworld.com as a freelancer....

man... The body corporate need guys like you

... only if I get to roam the world fixing kit and carrying out good deeds.

hmmmm

believe me,

you get tired of doing 5 countries in 30 days especially the good deeds bit.. (beaurocracy, customs corruption, underhand dealings to clear your tools, test kit and spare parts etc etc etc...)

However, there are some endeeming features that might enduce a smile on your face when hanging around former soviet & Asian countries sometimes
(especially summer times on the caspian & Indonesian beaches....)

For Firestorm, all the best in infiltrating the Occ Health market in the UK. I'll try and support as best I can (When I can)

just pop a pm when you need any help dude!

Either way, once I've finished the latest round of revisions on my software project (which, it must be said, has turned into something of a marathon exercise), I might just set off anyway. I can't see that I'm doing a whole lot of good here in the UK.

Regarding audiometers ... First of all, my guess is that the query relates to audiometric screening in PHC's. If I was landed that task, I think I would settle for calibration checks (only). Modern kit will usually pass muster anyway (just as long as the bar isn't set too - and unnecessarily - high).

And if calibration per se was actually needed, I would track down an NHS biomed shed already set up with the right kit, and sub it out to them! OK, next question ...

Geoff... (See my PM)

Firestorm, send me a pm and I'll forward you some brilliant material on affordble cal kit for audiometers that you can use in the field. You won't need a soundproof booth to do what you have to...

believe me, I've used these items on a copper mine in the DRC and I'll wager a few dimes on anyone to get better results on audiometer cals in the field

Hi Firestorm

I calibrate quite a few audiometers, in the workshop and in the field. While a soundproof booth is not exactly essential, a copper mine is not ideal...! But top marks to Jandre for achieving it.

The advice I can give you is that the test kit - and the subsequent validated calibration of same per year - is pretty darn expensive! I reckon my kit replaced piece for piece as it stands would be about £20,000 new and it is approximately £4000 a time (which should be every year) to calibrate to UKAS standards.

Calibrating anything out of standards in the UK would invalidate any audiograms taken with the equipment, so you really could do with getting acquainted with the latest British and International standards. They are not cheap to purchase!

After that, if you are doing Kamplex or GN Resound (ex Madsen) items, I can probably help out somewhat with advice.

I was trying to create some training notes for one of my colleagues. If I can get them into a reasonable state, they might give you something to base your further decisions on.

Out of the UK, you would probably have to be out of the USA/EU/Canada/Australia to get away with not sticking to the standards!

If you still want to give it a go and have the kit, I would be happy to advise, and I know a local biomed who now does only audio calibration who is a great source of advice and reassurance in the Manchester area. Just send a PM.

Does this local biomed get here on the forum?

I would be interested to learn how often the kit is out of spec (and by how much) during annual re-cal.

Also, surely the requirements (+/- percentage error at frequencies across the range of interest) are (or should be) different depending upon whether an audiometer is for screening or diagnostic use?

As you may imagine, I have always thought that annual calibration of audiometers was not really necessary, and would have thought that modern units were as "accurate" as the test equipment anyway.

Clinically, why do they actually need to be any more accurate than my old signal generator?

Surely modern audiometers don't "drift"? Aren't they digital ... software driven, even (and therefore only needing to be calibrated once - during manufacture ... and then only following repair, should this ever be needed)? And how would you adjust them (to bring them back into spec) anyway? Do they still have pots to twiddle?

Linking to the post I've just made under the Latest News thread ... another project that I've yet to get around to is an MP3 player - Bluetooth - whatever - earpiece device that would block my tinnitus and enhance the higher frequencies where my old ears (the left one especially) fall off (as it were). A high-tech (programmable) hearing aid. Does anyone have any news about things like this?

Or, better yet, does anyone have any information about the brain's data bus ... and where I can get at it? Would RS-232 do the trick, I wonder?

I don't think my contact comes on here. He spends most of his time travelling between audiology departments, when he isn't actually in them!

As to the amount of slippage on the audiometers:

1. An annual check does at least highlight if there is a problem with the cables to the headphones, which can be subtle to the ear but blindingly obvious on test gear.

2. The tolerances are twofold. The frequency tolerances are different between the different grades of machine, from screener at 3% to clinical at 1%. However, the intensity (volume) tolerances are essentially the same, at 3dB for all frequencies up to 4kHZ, and 5dB at 6 - 8kHz, regardless of the grade of machine.

3. Most modern machines (except the most basic screeners) now use ADC digital calibration techniques, with the most usual change step being 0.5 or 1.0dB. There are still some where the only adjustment is through twiddling pots. I quite like to see how close I can get them, but some machines are just a nightmare.

4. As to year-on-year accuracy, most decent equipment is fairly stable. Unfortunately, there are quite a few companies who sell really shoddy audiometers very cheaply, and the results speak for themselves...

5. As I said earlier, the calibration is tied up with the standards that the audiologists work to. They are a highly regulated profession, and an audiogram may be presented in court as evidence. It is (AFAIK) a legal part of being an audiologist, to ensure that your equipment has a valid calibration certificate when you perform audiological testing.

6. The accuracy might not be a completely clinical need - though with modern digital hearing aids, you can do such amazing stuff that it is worth tuning them as best you can. The real issue is that there needs to be a consistency of results. It is silly to have a hearing test at one centre, but find that the same results would be different down the road. Especially when the hearing aids might not be programmed using the same equipment or in the same department as that where the tests were recorded.

Building your own tinnitus/hearing aid device sounds really interesting! However, if you go to your local audiology centre, they should be able to provide you with all sorts of wonderful support that would do the same job. The latest tympanograph equipment we have already uses Bluetooth to download results, so it is only a matter of a few nanoseconds before they start using it to programme hearing aids.

So you reckon that £ 4,000 a year to have your test kit calibrated is money well spent, then?

What kit are we talking about there, by the way, a sound level meter reading dB's ... and a frequency counter?

Screening -> you either need a hearing aid, or you don't! Nothing much more than a "Go/No Go" test. Not much need for "precision" there, then.

Clinical -> an accurate audiogram, often used to support some sort of claim against someone for loss of hearing acuity. How much is a person's hearing worth? How come us ex-Forces people were told that it was "just" an "occupational hazard"!

Personally, I don't trust any of the quacks (on the grounds that none of them have done anything for me, or my immediate family, that I hadn't already made a great fuss about before they decided to "act"). So yes, if I do anything about my tinnitus, it will be on a "self-help" basis, as usual.

By the way, you may be interested to hear (oh yes, a pun) that the ringing in my left ear has become more pronounced (that is, I've become more aware of it ... it's always there) over the course of these couple of posts ... suggesting, perhaps, that the brain normally tends to "block it out" (filter it out), if left to its own devices.

For those interested in this sad case, I've suffered with it for 39 years now (yes, I can remember the actual cause ... climbing up onto the back decks of a tank, just as the gun was fired), it hasn't got worse, but neither has it improved. Someone once told me that (if I'm lucky) it might suddenly sort itself out (as it has been known that damaged nerves can regenerate, or whatever it is they have to do). But let's just say that "hi-fi" is a bit wasted on me!

We have all our audiometric equipment calibrated on site annually by a major leader in audiometric calibration. A certificate is provided for each item and an EST is completed.
The cost includes any minor repairs and adjustments to meet calibration requirements.
Its certainly much lower cost than the cost of having test equipment calibrated to UKAS standards and it also means that we do not tamper with equipment that we know very little about.

Sounds like the wise and sensible route to me.

But I rather suspect that the originator of this thread (from whom, I notice, we haven't heard since) has aspirations about becoming a "major leader" himself (themselves)!

I have actually been in the Audiology department when a student came to speak to the senior audiologist about the audiogram she had just taken.

The subject was a fit and healthy young man, but for some reason his fairly normal hearing test showed a sudden glitch at about 3kHz on the left side. The right was fine.

The senior audiologist asked his profession - he is an infantryman. The strange reading was a result of his occupation - he had forgotten to put his ear defenders on while firing his army rifle just once...

As to £4000 a year being worth it - no, Geoff I think not! But we're stuck with it. Frotunately, the number of calibrations and an arrangement whereby we look after the local doctors' surgeries equipment, means that the burden is lessened. We also used our Quality System to assess the need for the frequency of testing. This showed taht our kit does not drift much at all, so we decided that the risk was sufficiently small to accomodate testing only once every two years.

Yes ... a Risk Assessment (not always easy to apply ideas like that, though, in the heat of battle)!

Well if the originator was serious about starting up a service, he has quite a bit of stuff to look into. If he was casually thinking "nice little earner" he might have been put off!

Either way, like many other things when you start to look into them, calibration can be a real can of worms.

There are so many companies making and calibrating the kit that in order to make a serious go of it, it really would be best to join another such service and get some experience first.

I would go as far as to say that calibration itself (and I'm thinking of medical test equipment here) is the real "nice little earner"!

But (once again) I'm wondering why the mighty NHS doesn't have a central cal lab of its own!