EBME Forums Forums Maintenance Technical Assistance Audiometers... A case in question

periodically we are asked to do performance verifiaction on basic audiometers used in the occupational health environment.

With basic I mean the cheapest nastiest and probably oldest (technology wise) pure tone audiometers available on the market today.

Recently we decided to invest in brand new calibration kit and being a responsible company we are investigating the options first.

Auscco seems to have the best system that can almost make coffee doing the bone vibration thing etc etc
Price: $ 17,000.00 for the whole shebang (and probably the package we will go for unless Larson Davis can convince me to buy their package that can only run on XP and older OS systems)

Larson Davis is not far behind either.
Full package @ $12,000

Norsonic only want to play with the big boys...
Can't remember the price but from what the other 2 offer there's no argue that this is low key

This brings me to the case in question. I took my old quest unit and did a measurement on an amplaid unit. Afterwards I mounted the earphone on my Viayo laptop microphone (Yes the one right next to the motion eye on the tft display)and did a measurement with ARTA audio analysis software followed by a measurement using SIGVIEW audio analysis software. (Both available from the web for full functional trial download)

Guess what... The outputs were exactly the same as my Quest system with external SPL meter with pre-amp and artificial ear (All of which was recently calibrated)

Am I going mad or is there something the Audiometer OEM's are not telling us???

Yes ... the OEM's don't like folk knowing that you can sometimes (often, usually in fact) do something for nothing, or next to nothing, that they like to charge you $$$'s for.

It's called gouging, Jandre. But, as you have amply demonstrated, those with a bit of nous (mukh, whatever) can sometimes "beat the system".

Well done, Mate!

I bet if you can find a diaphraghm based speaker (Kind of in-ear) speakers and stack a tone generator sequence on either Sigview or ARTA you should be able to create an artificial mastoid. That will sort that side out as well.

I may be totally unenlightened and ignorant here and perhaps fell off the proverbial horse at high spead but something tells me that this must be possible

If indeed the case, one should be able to do full audiometer calibration for less than $200-00

Maybe someone knows how the mastoid couplers work and enlighten us all

Steady on, Jandre ... you'll be putting the gougers out of business, Mate. Ha, ha.

Do you come across many audiometers that are out of cal, by the way?

Lastly, have you checked out these articles:-

One
Two

Jandre

I found out that to replace the calibration kit I have would easily cost about £20,000 (UK). This kit is from Bruel and Kjaer. It would come fully calibrated to the UKAS standards, which we have to use to show traceability of the calibration for our service users. This is the key issue.

If in South Africa you have a set of nationally set and recognised calibration standards, you MUST comply with them, and however admirable and accurate your experiment is with the computer, there is no way around it. I do like the spirit of enquiry and scientific experiment, though!

The air conduction phones most normally used in audiology are the TDH39Ps in audiograms, and the B71 bone conductor. The International Standards (and British Standards) are based on these cups, and also on the tension in the headband being just right so that the force over the ear eliminates background noise to the same degree.

Using alternatives - while so far you have found no deviation - does leave the potential for inaccuracy. I have before now had to deal with an audiometer from a doctor's surgery where someone had lost the real phones and fitted spares from their personal cassette player... needless to say, they did not do the job!

If you need any kind of benchmark, the calibration costs for our artificial ear and artificial mastoid, sound generator and associated sound level meter touch £4000 a time.

While the British Standards say we need to calibrate the equipment every year, we have used the calibration history (back to 1992) to show that it has never deviated sufficiently to be outside the error margin.

This data analysis allowed us to carry out a Risk Assessment using another British Standard and safely move the scheduled validation to once every two years.

It all sounds a bit bureaucratic, but the audiologists here must ensure that they always use audiometers calibrated to the correct standards in the correct way. They can lose their registration to practice if they knowingly do not do so. So we are not just covering ourselves, but loads of other people too.

Thanks for that contribution, Clare.

If I were Jandre, I think I would make a clear distinction between audiometer "performance verification checks" and calibration per se.

Hence my earlier query about how many audiometers has he actually found to be out of cal!

Meanwhile, here is the Type 4930 Artifical Mastoid.

As an aside, I have found several audiometers out of calibration over the years. Usually there is a really obvious reason (things rattling that shouldn't, suspicious lumps missing from the side of the case, dents, bends, frayed wires, the usual...) but sometimes not, and this is why calibration is so important. How else are you going to find out whether something is working if you never check?

The worst problem at the moment is that companies more and more try to tie customers into sending equipment back to them for calibration instead of using their local independent or NHS calibration service. They fit individual passwords, or try to refuse to sell service manuals, etc

In fact, I actively discourage anyone who asks my advice from buying their equipment if they do this - and I know others do too. So there. If you make cheap end screener audiometers and your business has slackened off up North in the last few years, now you know why!

Bravo! Clare ... but again I make the distinction between checking performance and actual calibration (which should mean adjustments if such are indicated).

PM - yes. EST - yes. Damage checks - yes. Repairs - yes ... and then a re-cal. But otherwise, why not only re-cal when the unit actually needs it? OK, you are probably bound by tightly defined regulations, but somehow I doubt that Jandre is.

The "Highest International Standards" (meaning ... choose the one that suits you best), or any other standard specified by the Client (and, therefore, paid for) - always used to suffice "back in my day"! What (non-UK, non-EU etc.) client will be prepared to pay for all that calibration work ... just to prove that the instrument was OK after all?

Out there in the Real World, if Jandre & Co. can't check-out audiometers for less than $ x a go, you can be sure that someone else will be found who can (or at least say he can)!

It all depends whereabouts Jandre is. Especially in Occupational Health, there is a potential that the results of the audiogram could become the subject of a court case (for industrial hearing damage, etc). In the UK we usually use these hearing tests on factory or mining workers, which would be my best guess as to where the equipment is being used in RSA.

I may be wrong, but if people are taking the hearing health of employees seriously enough to test it, they are also going to have to have some sort of standardisation to work toward. The court will need that to be able to come to a fair decision.

In the Real World, most of us are smart enough to realise that an offer that looks or sounds too good to be true usually is too good to be true.

Jandre really needs to price up the new equipment, but also press to find out what the ongoing costs will be with the validation calibration of his kit to the locally required standards. Then, he needs to assess what the overall demand is for him to provide the service. If the purchase and running costs are easily spread out into a fair charge per audiometer that also accounts for (say) one hour at his standard rate, then he is winning. If not, it is not worth the hassle.

I’ve no argument with any of that.

I’ll let Jandre respond for himself ... but not necessarily from South Africa. Suffice to say that, if you take a look at Jandre’s various posts, you will find many clues to the kind of locations he visits.

I also strongly suspect that he is obliged to check-out the audiometers he finds at those locations, along with all the other medical equipment items on the list. Not much chance to "dip the shoulder" there, I’m afraid.

And (lastly) don’t forget that, whatever test equipment he needs has to be lugged and bumped about all over the place in (again, I suspect) less than ideal conditions. So ... quite apart from the physical demands involved, how in-cal is the test kit, I wonder?