What is Hearing Loss?
The term “hearing loss” encompasses the following terms -:
Hearing impairment, deafness, deafened, partially deaf, hard of hearing.
Levels of deafness can be divided into different categories using the following definitions.
| Severity of deafness | Range of hearing loss in decibels (dBHL) |
|---|---|
| Mild deafness | A child with mild deafness has 21 to 40 decibels of hearing loss (dBHL) on average in their better ear. |
| Moderate deafness | A child with moderate deafness has 41 to 70 decibels of hearing loss (dBHL) on average in their better ear. |
| Severe deafness | A child with severe deafness has 71 to 95 decibels of hearing loss (dBHL) on average in their better ear. |
| Profound deafness | A child with profound deafness has more than 95 decibels of hearing loss (dBHL) on average in their better ear. |
Hearing loss can also be subdivided into -:
Conductive hearing loss - resulting from interference with the passage of sound through the external and middle ear to the inner ear.
Sensorineural hearing loss - resulting from disorders of the cochlea
(in the inner ear) or the auditory nerve and its central connections and may be associated with a loss of sound discrimination.
Prelingual deafness means that the child was born deaf or became deaf before the development of language skills.
Figure 1 - Anatomy of the ear
Anatomically, the ear is divided into three parts, the outer, middle and inner ear.
The outer ear consists of the trumpet shaped auricle or pinna and the external auditory meatus (outer ear canal), which together funnels sound to the middle ear. The middle ear is separated from the outer ear by the eardrum or tympanic membrane. It is an air filled cavity in the temporal bone of the skull, connected to the throat through the Eustachian tube. The three auditory ossicles, malleus, incus and stapes are small bones that provide a mechanical link between the tympanic membrane and inner ear. The inner ear is divided into the organ of balance (vestibular labyrinth) and the organ of hearing (the cochlea). This contains the Organ of Corti and its thousands of sensory hair nerve cells. The nerve of hearing or auditory nerve passes to the brain from the inner ear.
Incidence/Prevalence
There are no comprehensive national statistics on the number of children and young people in the UK with hearing loss. The best estimate on the total number of children and young people aged 0 – 25 in the UK with permanent bilateral (affecting both ears) hearing loss (greater than 40dBHL) is 34,800. About 840 children are born in the UK every year with moderate to profound bilateral sensorineural deafness. About 50-90 percent of permanent childhood hearing impairment may develop after birth.
Thousands more children will experience mild to moderate deafness. A child with this level of deafness can hear some sounds, so it may be harder to recognise that they have some level of hearing loss.
