When someone suffers from hearing loss, it does not mean that he cannot hear anything at all. The human auditory system can detect sounds of various pitches or frequencies – more specifically, our hearing range is from 20 Hz to 20,000 Hz.
Afiqah Amirullah, Audiologist
Hence, hearing loss can occur anywhere within this range. One person may have hearing loss affecting only the high frequencies. Another person may suffer from hearing loss ranging from mid - high frequencies. And it is important to note that the hearing loss can vary from mild, moderate, severe, and profound.
The frequency range of different musical instruments. Taken from www.har-bal.com
Let’s take a closer look at the different degrees of hearing loss and its impacts.
First, it is important to introduce the audiogram so that it is easier for us to understand. According to the British Society of Audiology, an audiogram is “a graph which plots the quietest level that you can hear at each frequency tested.” An example of an audiogram is shown below:
The horizontal axis represents the pitch or frequency in Hertz (Hz0, ranging from 250 Hz (low frequency) on the far left, to 8,000 Hz (high frequency) on the far right. The vertical axis, on the other hand, represents the hearing threshold in decibels (dB). Sounds further up the axis are very soft (softest at -10 dB on the audiogram), and sounds further down the axis are louder (loudest being 120 dB on the audiogram).
So what is considered as “normal hearing”? At which level on the audiogram is a hearing loss diagnosed? The audiogram below depicts the different degrees of hearing loss:
A person with normal hearing should have hearing thresholds within the range
of -10dB
HL to 20 dB HL.
A
mild hearing loss is diagnosed when a person has hearing
thresholds ranging from 25 dB HL to 40 dB HL.
As for moderate hearing
loss, the range is from 45 dB HL to 65 dB HL.
Severe hearing loss is diagnosed when the
hearing thresholds fall between 70 dB HL to 85 dB HL.
And lastly, profound hearing loss is diagnosed as hearing thresholds that fall between 90 dB HL to 120
dB HL.
But what does this mean? What are the effects of these different degrees of hearing loss on a person’s daily life? The following image shows the examples of sounds found in our environments and where it falls on the audiogram:
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We can see from the audiogram of familiar sounds show that different sounds fall at different frequencies and at different loudness levels. It is important to note down that different speech sounds also fall at different points on the audiogram. Hence, hearing loss affecting different frequencies will affect the perception of different speech sounds as well as environmental sounds. Let’s see some examples below.
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Audiogram depicting mild hearing loss at mid to high frequencies on the right ear
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Mild hearing loss can make it difficult for the person suffering from it to listen to really soft sounds like whispers, leaves rustling, or birds tweeting. As depicted in the audiogram above, this person may have difficulties hearing speech sounds at the higher frequencies, such as “k,” “f,” “s,” and “th” sounds, especially if these sounds are spoken really softly or from afar, or if there is competing background noises. However, in quiet places, those with mild hearing loss would still be able to listen to and understand speech spoken at normal conversational levels, which typically fall between 40 – 60 dB HL.
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Audiogram depicting moderate hearing loss on the left ear
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This
second audiogram shows a person with moderate
hearing loss. It can be seen that this person will have trouble
listening to conversations, even more so when there is background noise. A
person with moderate hearing loss may require frequent repetitions and may have
problems listening in group situations.
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| Audiogram depicting severe hearing loss on the left ear, and profound hearing loss on the right ear |
Lastly, we have an audiogram showing severe hearing loss on the left ear, and profound hearing loss on the right ear.
Those with severe hearing loss will definitely have problems hearing speech sounds, whether in quiet or noisy environments, as all speech sounds are softer than where the hearing threshold is. However, they may still be able to hear loud environmental sounds such as vehicles passing on a highway, the sound of gunshots, and the sound of an aeroplane taking off or landing.
On the other hand, those with profound hearing loss may not be able to hear these loud background sounds. Often, this can be a cause of concern, as loud warning sounds like the fire alarm or the ambulance is important in determining one’s safety.
Sources:
http://www.thebsa.org.uk/public-engagement/faqs/
http://www.thebsa.org.uk/wp-content/uploads/2014/04/BSA_RP_PTA_FINAL_24Sept11_MinorAmend06Feb12.pdf
www.har-bal.com
Written by:
Afiqah Amirullah;
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