Monday, 14 April 2014

Audiograms? Hearing Tests? What's that all about?

As part of the application process for a Hearing Dog I had to send an up-to-date Audiogram to the Hearing Dogs person who is my Application Advisor, we'll stick with calling her Freda for the time being. 

This is a copy of my Audiogram from 3 years ago, my hearing hasn't changed a great deal over the years but I fully expect it to deteriorate at some point due to age related hearing loss (more on that another time). 

For those who have not had a hearing test the Audiogram is the results of the test, that the patient (in this case me) has undergone, in graph form.

The Hearing Test (we'll call it that for simplicity!) is undertaken in a soundproofed room free from outside noise. Often the rooms are windowless and the walls are lined with soundproofing materials in older rooms. More modern rooms are more conventionally decorated with wallpaper etc.but may be soundproofed underneath.

The room will either be in two parts with a soundproofed partition with a double/triple glazed window separating the audiologist and the patient or will be a single room in which both the patient and audiologist sit together.

The test is conducted without Hearing Aids and the patient wears a set of headphones connected to a console in front of the audiologist that is used to generate sounds at different frequencies (tones e.g. Bass through to Treble, and beyond, if you like) and volumes (dB or decibels in technical parlance).

The test is carried out annually for younger patients or patients who have recently been diagnosed as having a hearing loss. In my case I visited the Royal Throat Nose and Ear Hospital in London on an annual basis from the age of three (more about the time prior to this in a future post) until around the age of 20 (mostly in Spring) after which I went bi-annually and now less frequently.

In the old days (blimey, makes me sound old!) when the audiologist generated a sound via the console the patient (me) would be required to tap the edge of the desk/table with a drumstick (this I found very childish and slightly embarassing when I got old enough to feel above all that kind of thing)! When technology moved on a bit, or more likely it needed replacing and could be afforded, the drumstick was replaced with a hand-held button to press when you heard the noise generated.

The test goes on for what seems like an eternity, but is usually around half an hour I think. and for various reasons requires a considerable amount of concentration as will become apparent later. The Audiologist will play a series of tones (noise frequencies, Bass > Treble etc remember) that are randomly louder or quieter (it seems random to me but there is apparently a protocol or structure behind all this). Each time the patient hears a noise that is distinct they press the button. The problems for me arise at this point.

Since the brain is a smart thing, it gets easily bored. Due to this boredom it sometimes makes up noises of its own; this is what is called Tinnitus. Tinnitus isn't necessarily a 'ringing of the ears' as it's often described; the noises can take many forms and can happen at varying times. In my case, within the hearing test environment, I often get, what I think are, echoes of the sounds that are being made by the Audiologist which adds an extra level of complexity and doubt into the equation. This also means that I really have to concentrate, especially on the quieter sounds that I can detect to be sure that I am responding to a genuine sound rather than a self-generated sound (if that makes sense). There are further aspects to Tinnitus that affect me outside of the Hearing Test and I'll cover these another time.
Anyway, back to the test. Each set of tones is played out at varying volumes (db/Decibel levels) and the Audiologist notes the positive responses the patient makes before moving onto the next set of tones. Louder noises are easier to respond to and quieter noises require a lot more concentration and consideration. The best responses, i.e. the quietest sound the patient can hear (lowest number of Decibels for each tone range) are marked on the Audiogram with a blue X for the left ear and a Red O for the right ear.

The range these values fall into enable different levels of Hearing Loss to be categorised, from this we can see which broad category the patient falls into (I am on the boundary between two).

If you'd like some idea of what the sounds 'played' are like take a visit to this site and select the 1KHz sound (make sure your speakers aren't too loud and that you choose the 5 second file rather than the 30 second file otherwise you'll never forgive me!) which is the sound in the mid-point of the X-Axis on the Audiogram. Feel free to try the other sounds as well although, apart from the 250Hz sound, these do not appear on the graph.

I hope this helps give some understanding of what the hearing test is like and how the results are generated and interpreted.

(Below is an extract from the Action On Hearing Loss website explaining the different hearing loss levels)
There are four different levels of hearing loss, defined by the quietest sound that people are able to hear, measured in decibels (dB).
Mild hearing loss:
Quietest sound: 25 - 39 dB.
Can sometimes make following speech difficult, particularly in noisy situations.
Moderate hearing loss:
Quietest sound: 40 - 69 dB.
May have difficulty following speech without hearing aids.
Severe hearing loss:
Quietest sound: 70 - 94 dB.
Usually need to lipread or use sign language, even with hearing aids.
Profound deafness:
Quietest sound: 95 dB+
Usually need to lipread or use sign language

1 comment:

  1. I followed your link to the audio test Mike and was listening to the different sounds. Millie was intrigued by the 440Hz!

    Love the blog. I only had time to dip into it today but shall have a good read when I can. More on the lovely Alvin please!! See you over the Common :) X