Why Audiometer Calibration Is Key To Accurate Hearing Testing

We are all acutely aware of the fact that in order to stay healthy we need to exercise. We are especially aware after a long cold winter or summer vacation. While the list of benefits we gain from physical activity including longer life, improved vitality and weight-loss, many of us still don’t do it.

But what on earth does exercise have to do with audiometers?

Actually, it’s not just audiometers. Most “measurement” equipment needs it and medical devices, especially so.

Imagining an ECG doing lunges or a stethoscope in a yoga pose may bring a smile to your face but it is obvious that equipment can’t exactly “get physical”.

“Exercise” falls within the domain of maintenance, and whether you are putting on your running shoes or having your equipment serviced, both are equally important to ensuring quality and longevity.

Exercise has a direct benefit to ourselves, our bodies and by extension, our lives. Similarly, not exercising also affects only ourselves. A sedentary lifestyle may set a bad example but won’t directly affect our neighbours, friends or family.

Servicing and calibrating medical equipment has vastly different repercussions.

Failure to do so will affect others (i.e. patients).

Regulations require that medical equipment is maintained regularly. Some standards are more stringent than others but in any country, it is a must. Failure to comply to these regulations or standards can have severe legal and financial consequences.

In the occupational health screening setting where high volume testing is the norm, having to retest patients for free can cost you dearly. Penalties may also be applied and licenses may hang in the balance.

Incorrect diagnosis, in all settings, can lead to legal liability on the part of the practitioner, severely affect patients and, in industrial settings, the customer can also face heavy damages.

In short, exercise is good for you, audiometer calibration and maintenance is good for everyone. basis.

So, What Is Calibration?

Calibration is the process of configuring an instrument to provide an accurate result for a sample within the acceptable range provided by the applicable standard. In our case, audiometers.

For audiometers, calibration verifies that the tones being presented across the frequency spectrum are within the required parameters. It ensures that when an audiometer is instructed to present a 500 Hz tone at 10 dB the correct values are received by the patient. It is a guarantee that the tones are accurate and so are the test results.

Types Of Calibration

There are two main methods of calibration that must be completed at a regular basis. Commonly referred to as electro-acoustic calibration and biological/subjective testing.

Electro-acoustic Calibration(EAC)

EAC is performed by a qualified technician in laboratory or within laboratory conditions. Generally conducted on an annual basis, EAC verifies that the decibels and hertz are correctly presented according to the number of wavelengths per second and the volume respectively. EAC determines the current output of the device. Once determined, adjustments can be made to ensure correct output.

Once calibrated, you will be issued with a calibration certificate proving that the device is suitable for use. This will include the date of calibration which determines the period of validity.

Note: It is common for audiometer manufacturers to stipulate a calibration interval of at least once per year. Some standards require different calibration intervals and supersede the manufacturers recommendations. E.g. In South Africa, all portable audiometers used in occupational health should be calibrated at least every 3 months.

Biological/Subjective Testing

This calibration is the clinician/user’s way of verifying that the audiometer being used is still within calibration norms and is working as expected. This biological/subjective test should be performed on a daily basis prior to testing and does not replace EAC.

Generally, this test is performed on a human subject of known hearing values. To do this a person with normal hearing levels is tested on both ears, the transducers are then swapped around and the test repeated. Note that you are using the same ear to test both transducers, so the results should be similar. The results should be within 0 – 10 dB of each other. If not, the audiometer should be re-calibrated (electro-acoustic) prior to using the audiometer again.

There is an easier and quicker way of doing this with a tool that now comes standard with all KUDUwave Devices. X-check (cross-check) is a digital calibration verification tool built into the device. It enables accurate (within 5dB) calibration verification to objectively ensure the precision of your results. This turns a traditionally “subjective” test which can be affected by the subject’s health into an objective and highly accurate test.

Using X-check is really easy and will save you a ton of time and grey hair.

It’s clear that, like exercise, calibration, calibration checks and servicing are vital in ensuring the quality of medical devices and the results they produce. While there is cost and effort involved, these don’t outweigh the benefits in terms of quality of test results, patient care and risk management.

Unlike exercise, maintenance is as vital to you as the professional as it is to the patient, company and healthcare system as a whole.