Your audiogram explained

The audiogram plots the level of hearing in each ear separately.  The plots on it show the quietest sounds you can hear at each of the frequencies tested.

In the graph below the red circles represent the right ear and the blue crosses represent the left ear. Across the top, there is a measure of frequency (pitch) from the lower pitched sounds on the left going to higher pitched sounds on the right. Each red circle and blue cross represents the individual frequencies of sound that have been presented in the hearing test. These frequencies are measured in Hertz.

Down the side of the audiogram, there is a measure of loudness. At the top of the graph are the very quiet sounds, going down to moderate, and then very loud sounds. The points (red circles and blue crosses) marked on the graph represent the quietest sound which can be heard at each of the frequencies tested. These plots show the ‘hearing threshold’ for that particular frequency.  The loudness is measured in a scale called decibels (dB).  Plots on the graph at 20dB or quieter are considered to be within the normal range.

 

Audiol1

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The lower down the graph the points are plotted, the worse is the hearing. The different shaded areas indicate the different classifications of hearing loss. For example, if an individual’s thresholds were all between 40 and 60 dB we would say they have a moderate hearing loss.

The most common way of helping someone with a hearing loss is to fit hearing aids. However with more severe hearing loss it is more difficult to provide satisfactory hearing aids as the cochlear hair cells may be few and far between.
When the plots on the graph are in the region of 100dB, the hearing loss is so severe as to make finding a suitable aid difficult. This is because maximum amplification will result in distortion of the sound that is heard.  Hearing aids cannot replace lost nerve cells in the cochlear.  However some technically advanced modern digital aids can reprocess sounds to a lower frequency pitch that can be recognised.

The audiogram in age related hearing loss

Presbyacusis is the scientific name which is given for age related hearing loss. It usually affects the high frequencies more than the low frequencies. The audiogram  below shows the sounds have to be made louder before they are heard in the high frequencies (the right side of the audiogram), leading to a slope on the audiogram as seen below. This audiogram shows normal hearing up to 1KHz (mid frequency) and a mild hearing loss in the mid to high frequencies. Depending on the degree of the hearing loss, the sounds in the higher frequencies have to be made louder.   The general pattern is likely to be similar for all presbyacusis hearing loss.  This is a right hand sloping hearing loss with the both ears usually deteriorating at equal rates.

 

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Speech sounds and the audiogram

This audiogram below shows hearing within normal limits.  It also shows speech sound as they would be heard during a ‘normal’ conversation.   The thresholds of hearing on this audiogram are well above the speech sounds.  We therefore know the patient can hear all these speech sounds as they are louder (lower on the graph audiogram) than the thresholds at these particular frequencies.

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In the audiogram below, the hearing ‘threshold’ of the patient’s audiogram dips below 25dB in the higher frequencies.  This is the level some speech sounds (f,s,th and k) are not heard in normal conversation. The result is that speech sound muffled for that person or they might complain that people mumble.  By aiding (amplifying) these frequencies, we aim to make these speech sounds audible, and therefore make it easier for the patient to hear and understand speech.
Women’s and children’s voices tend to be of a higher frequency compared to men and thus harder to hear with a high frequency hearing loss.

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ConsonantsSevere high frequency hearing loss

  • The aim of the hearing aid is to raise the threshold of hearing at the frequencies lost, without increasing the overall sound, so that the conversation sounds (f,s, th and k) can be heard.
  • At the frequencies where the hair cells of the cochlear are effectively not working (80-90dB) amplification will achieve very little.  The very latest technology is then needed.
  • If your hearing loss is severe or even moderately severe an insight into your own audiogram would help the decision as to the benefit of a listening device. (Link to top of page)

This audiogram also shows the loudness and pitch at which environmental sounds are made.

 

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