The MedRx A2D audiometer I use to test hearing is calibrated on an annual basis and is recognised as one of the most robust and accurate portable audiometers on the market.
One of many reasons for using this particular audiometer is that it allows for insert earphone testing rather than what is technically known as ‘supra-aural’ headphones (the over the head style that you’ll be familiar with if you have ever used hi-fi style headphones.)
Why is this important?
Well, if you think about where the sound outlet for a hearing aid will sit (regardless of the style of the aid) the sound is delivered into the ear canal itself, not the bowl part of the outer ear (the medical term is the ‘concha’). So, if that bowl part is where traditional headphones send the ‘testing’ sound to, it will likely affect your results. This might not seem like much of a distance, but a centimetre or two can make up to a 10-decibel difference in test results, leading to the very high possibility of any hearing aid that has been programmed based on those test results sounding too loud.
Have you ever heard someone say ‘My hearing aids just make everything sound louder’?
Over-amplification is often the cause (though not the only cause – as you will see in my forthcoming blog on directional microphones.) Wouldn’t it simply be better to conduct the hearing test itself in exactly the same anatomical position as the hearing aid will sit?
Could this lead to a more precise ‘prescription’?
It’s a resounding YES to both of those questions, which is why I only ever conduct hearing tests using disposable insert earphones. They may cost me a little more, but your hearing is worth that investment.