29 March 2021
Our hearing is a complex sense that most of us take for granted until we lose it. Many things can cause hearing loss, and we will most likely experience some degree of decreased hearing with age. A diagnostic hearing test is usually the first step on your way to better hearing health. But how do you read the audiogram charts that display the result of your test? In today’s post, we’ll help you to interpret your audiogram results!
An audiogram measures your hearing ability and the degree of your hearing loss. It is, simply put, a graph that shows the softest sounds you can hear at different frequencies and pitches. Below you can see a blank audiogram. The numbers on the top ranking from 125 to 8000, are indicators for sounds frequencies. The higher that number, the higher is the pitch of the sound. On the left side, you can see the units for loudness, which is measured in decibels. Just as an example: A face-to-face conversation is about 65 decibels.
Source: Aussie Deaf Kids
An audiogram can be read from left to right for frequency and from up to down for the intensity in decibels. By testing your hearing at different frequencies, your audiologist can ascertain which sounds are heard and which sounds are not. This is critical, as a hearing aid is tuned to make the sounds that cannot be heard louder, rather than just making all sounds louder.
The hearing assessment uses a battery of tests to ascertain your hearing abilities. The first and perhaps most fundamental test is pure tone audiometry. This test requires you to wear specially calibrated headphones and subsequently a specially calibrated bone conductor (which vibrates sounds through the skull). You’ll listen for tones which are presented via specially constructed electronic equipment, known as audiometer, an electric instrument created specifically for hearing tests.
The audiometer allows the audiologist to vary the frequency (the pitch) and intensity (the loudness) of tones. You’ll be instructed to indicate when you can first detect the tone at a specific frequency, usually by pressing a response button. In doing so, the audiologist can record these levels on a graph – the audiogram.
Threshold establishment determines what tones and what intensity can be heard. This is also used for calculating how much amplification will be applied by the hearing aid when the loss is present.
Pure tones, that is sounds at single frequencies, are used to test air and bone conduction and identify deficits. Once right and left ear air and bone conduction thresholds are established, they are recorded on the audiogram.
A summary of specific symbols used on audiograms and their meaning:
The results of the hearing test are an indication for the degrees of hearing loss:
But what does it mean to be diagnosed with hearing loss? And can a hearing aid help?
The phonemes of speech have been plotted on the audiogram below for their pitch and loudness. Low pitched phonemes are louder than high pitched phonemes. Unfortunately, hearing loss generally occurs with age at high frequency.
As soon as hearing sensitivity drops at high frequency, we begin to have difficulty hearing the sounds – f, s and th – which are commonly found at the beginning and the end of words. For example, an utterance such as “the car goes fast” may be heard as “the car goes past”, or “the car goes last” when a high-frequency loss is present. Should loss exist at low or mid-frequency, more difficulty hearing and understanding will occur, and a hearing aid will be required.
Here we see a moderate to severe mixed loss in both ears. Both the inner ear and the outer and/or middle ear are dysfunctional. A hearing aid is required and will result in significantly improved hearing.
In both examples above, the ears have similar thresholds (or symmetrical hearing loss). However, in many cases, hearing loss can be in one ear only – known as a unilateral hearing loss or there can be loss in each ear with one ear significantly more impaired than the other – this is known as asymmetrical hearing loss.
Below is an example of an audiogram with asymmetrical thresholds.
Hearing aids for each ear will be needed but there may be a difference in gained benefits due to the asymmetry. The benefit of a hearing aid is likely to be greater in the less impaired ear. A hearing aid for each ear can and is applied generally as this is generally better than a hearing aid to just one ear.
Pure-tone audiometry establishes your sensitivity to sounds which represent speech. But your ability to understand speech needs to be determined, too. Speech audiometry is the presentation of recorded lists of words presented at various levels of loudness. The words are scored at each presentation level for phonemes correct and recorded as a percentage.
Speech audiometry scores are indicative of how well you will hear with a hearing aid. Sensorineural loss often results in poorer speech understanding than mixed or conductive loss. Additionally, the greater the degree of loss, the poorer the speech scores are likely to be.
Sometimes with extremely poor speech understanding a hearing aid may be of limited or no assistance. Most people with hearing loss can be fitted with a hearing aid which will offer significant assistance in hearing speech and sounds well.
Below are examples of speech audiometry results for the various hearing loss categories. The score is recorded in the vertical axis against the level or loudness presented in the horizontal axis.
The higher the percentage understanding of speech, the more beneficial a hearing aid will be. Combining both pure-tone thresholds are speech audiometry results enables an understanding of what it means to have a hearing loss and the likely resultant effectiveness of a hearing aid.
The aim of hearing aid amplification is to restore your ability to hear speech sounds. Whilst it is possible to make sounds audible with a hearing aid, it is not always possible to make sounds understood.
‘Like sounding’ sounds can still be confused and the presence of noise, accented speech and/or poor articulation can result in difficulties hearing clearly. Modern hearing aids use advanced technology to reduce noise and accentuate speech sounds, whilst focussing the hearing aid’s microphones towards the speaker.
The resulting amplified sound is clearer and maximises the wearer’s ability to understand speech and differentiate between speech sounds. The hearing aid has extremely rapid processing of incoming sounds and almost instantaneous reproduction and amplification, minus the noise.
So, is a hearing aid worth it? In most cases, a resounding “yes” is the answer as you can expect improved localisation of sounds, awareness of sounds and improved understanding of speech from the hearing aid.
For more information about diagnostic hearing tests, pure tone testing and hearing aids, or to make an appointment with a local Attune Hearing clinic, book online or give us a call!
