Reading the Audiogram
As indicated above, the outcome of the hearing evaluation is a chart of the client’s hearing called an audiogram. The audiogram plots the loudness at which a series of frequencies must be played before they can be heard (audiometric thresholds).
Loudness: Measured in decibels hearing level (dB HL). It is represented on the vertical axis of the audiogram, from approximately 0 dB HL (very soft) to 110 dB HL (very loud).
Frequency: Sometimes called ‘pitch’ is measured in Hertz (Hz.). It is represented on the horizontal axis of the audiogram, from 250Hz (very low pitch) to 8000 Hz (very high pitch).
Degree of hearing loss: The audiometric thresholds indicate the severity of loss from mild, moderate, moderately-severe, severe through to profound.
We usually produce an audiogram for each ear. In these examples the two ears are shown on the one audiogram. The right ear thresholds are recorded on the audiogram as a O and the left ear thresholds are represented by X.
The first audiogram has thresholds for the right and left ears recorded. In this case, all thresholds fall within the normal hearing range (0 - 25 dB HL on the vertical axis).
Notice that hearing thresholds are not always exactly the same in each ear for each frequency, even when hearing is normal. This is also common with hearing loss.
High-frequency hearing loss
The most common type of hearing loss is high-frequency hearing loss. Here there is a milder hearing loss (or even normal hearing) for low-frequency sounds and a greater degree of hearing loss in the higher frequencies.
This second audiogram shows an example of a mild to moderately-severe, high-frequency hearing loss.
Type of Hearing Loss
The type of hearing loss – conductive, sensorineural, or mixed – can be determined by comparing results from testing done with earphones and that done with a special bone oscillator headband.
One ear or two?
In the vast majority of cases the hearing loss in one ear is very similar to that in the other. Indeed a significant variation between the two is one of the conditions warranting medical referral.
Where the loss is similar in both ears it is regarded as best practice, across the world, to recommend an aid for each ear. This is termed ‘binaural’.
It is only after the comprehensive hearing evaluation that recommendations may be made for further testing, referral, and/or treatment. Clients are referred to a physician for evaluation and treatment if an underlying medical condition is suspected, or if hearing aids are recommended, for medical clearance. In most cases of hearing loss, (including nearly 95% of sensorineural hearing losses), hearing aids are the treatment of choice.