Understanding hearing loss

By understanding your child’s hearing loss you can understand how much the technology enables your child to hear, listen and talk.

Developing listening and language starts with appropriate prescription of digital hearing aids. It continues because of the language that parents do naturally as they interact. Learning to Talk provides more information about how to help your deaf child learn to listen and talk.

There are different types of hearing loss and they are usually described in terms of the decibel level at different frequencies.

What are ‘decibels’?


An individual’s hearing loss is described in decibels. Decibels (dB) are used to measure the loudness of sound. A quiet whisper is about 30dB compared to normal conversation, which is about 60dB. The level of a shout close by would be about 80 or 90dB as would that of a lorry passing you in the street. A jet engine at 75 metres emits a noise of about 140dB.

What are the levels of hearing?


The point at which a sound can just be heard is called ‘the threshold’.

Normal Hearing (-15dB- 20dB)
Sounds can be heard at 20dB or less across all frequencies. All the sounds of speech can be heard clearly.

A mild loss (21dB – 40dB)
The child will hear that you are speaking, but will not be able discriminate the quieter elements of conversation which carry a lot of meaning.

A moderate loss (41dB -70dB)
Normal conversation will be difficult to hear without hearing aids.

A severe loss (71dB -95dB)
Access to normal speech conversation is not possible without hearing aid technology. Child may respond to loud sounds in the environment.

A profound loss (greater than 95dB)
Access to normal speech conversation is not possible without hearing aids. They will be completely dependent on hearing aid technology.

What is frequency’?


Where decibels are talking about loudness, frequency is talking about the range or pitch of hearing. Pitch is similar to the difference we hear between a low note played on a piano and a high note. The ‘higher’ the sound, the higher the frequency. Frequency is measured in Hertz (Hz) and kilo Hertz (1kHz = 1000 Hz).

The frequencies that are measured by your audiologist are the important sounds for speech development. Most vowel sounds (a,e,i,o,u) in English are low frequency but many consonants, like s, t, k, are high frequency.

Your child needs to have as much access to the frequency range for speech as is possible. Running speech has more frequency auditory information than single sounds and words. Your child will gain more from hearing normal pace of language including intonation, accent and clear context.

Hearing levels are usually plotted on an audiogram that identifies the decibels levels of loss and frequency range of loss. ‘Conversational speech levels’ and environmental sounds can be superimposed on the audiogram to aid interpretation.

What is an Audiogram?


An audiogram is a graph which shows how loud (ie the decibel level) sounds have to be at each frequency for the child to hear them Audiograms represent the loss for the right ( red O ) and the left ear ( Blue X) on the graph since the loss can be different in each ear.

Each child’s audiogram is different. Ask your child’s teacher of the deal to explain your child’s audiogram more fully.

Types of Hearing loss


Hearing levels are gained when the audiologists measures the response of the child to sounds going through the ear, middle ear and inner ear. The hearing difficulty can occur in any of these areas or can be a combination of each.

On the Audiogram ‘Air’ responses (Through the ear – middle ear – inner ear are recorded by the X and O ). It is possible to bypass the middle ear to test the Inner ear (cochlear). This is represented on the audiogram with a triangle ^.


What does a hearing aid do?


The audiologist will set up the digital hearing aid to match your child’s frequency and amplification needs.

In this way only the frequencies required will be amplified so your child will hear soft sounds and loud sounds will be controlled so that they will have a comfortable listening experience and hear all the frequencies required.