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Pure tone hearing tests and the Audiogram

The pure tone test is fundamental to audiology and it gives us the first indication of what you can and what you cannot hear.

Pure Tone Hearing Tests

The first test of hearing ability is pure tone audiometry.The audiologist will place headphones on your ears through which you are presented with a range of different pitched beeps (called pure tones) and asked to indicate by pressing a button when you can hear them. The presentations will be made separately to each ear.

The loudness of each tone is reduced until you can just hear the tone. The softest sounds you can hear are known as your hearing thresholds, and these are marked on a graph called an audiogram. Your audiogram tells us a lot about your specific hearing loss.

Pure tone tests and the Audiogram

The Audiogram

The audiogram is the graph which plots your hearing threshold resulting in a line which marks the softest sounds you can just hear at various frequencies or pitches.

The vertical axis shows loudness measured in decibels, and the horizontal frequency in herz (cycles per second). The further down the chart the plot appears the greater is the hearing loss, the further to the right, the higher the pitch.

The example chart shown here shows this clearly as well as an area known as the speech banana, showing where normal speech sounds are made. Note that consonant sound is high in pitch. Also shown are some common environmental sounds.Click here for a full screen version of this form.

Pure tone tests and the Audiogram

The Audiogram

This could be your audiogram if you had normal hearing. Your hearing threshold level is at zero decibels across all frequencies. You can hear any sound below this threshold (or louder than threshold) and as almost everything is below this line you can by definition hear all normal sounds.

This includes all of the sounds of speech, which are shown on the so called "speech banana" on this audiogram and all environmental sounds such as bird song at the pleasant end of the spectrum and a motorbike at the other end.

You will also hear music clearly and with all bass, treble and the harmonic timbre which make listening to it such a pleasure.

Pure tone tests and the Audiogram

Audiogram - normal hearing

If you suffered from a moderately severe high frequency hearing loss in your right ear, the audiogram would look like this. The further down the chart you are the greater your loss of hearing. Here the loss is greater in the high frequencies. Now the area above the line, the sounds you cannot hear become more significant.

Note how you would be better able to hear vowel than consonant sound. Vowels give speech a lot of its qualities of loudness and consonants its clarity , or understandability. You may often find that you know that people are speaking but you don't know what they are saying.

Notice how well you can still hear environmental noise and think about how much more difficult it would be for you to follow speech when in a noisy environment.

Music may be lacking a lot of softer treble sounds , it may have lost a lot of its brightness.

Pure tone tests and the Audiogram

Audiogram - moderate sensori neural hearing loss

We plot a threshold in two ways.

  • Through headphones via the ear canal and middle ear
  • Using a bone conductor straight into the inner ear or cochlea.

In this audiogram the direct to cochlea route (the braces at the top of the chart) produces a better result than the headphone route (the circles). This means that something is preventing the sound from conducting through the ear canal (could be wax) or middle ear cavity (could be fluid in the middle ear , or a more permanent malfunction of the tiny middle ear bones)

This is a conductive hearing loss and should, if it has not been previously cleared by a medical professional, be referred to one.

You would probably be feeling blocked up and your hearing would have lost qualities of both loudness and clarity.

Pure tone tests and the Audiogram

Audiogram conductive hearing loss