1. How to test a baby's or young children's hearing?
Paediatric section/ Baby's hearing health
The field of Audiology that deals with babies and kids (mostly less than 16-18 years of age) is Paediatric Audiology. This includes the same services (hearing assessment, diagnosis and rehabilitation) but incorporates various different methods keeping in mind that ability of the child. Most of the testing methods are highly age specific.
There are tests which are behavioural (that require the child to actively respond) and objective (i.e. does not require the co-operation of the child). Behavioural tests include Distraction test (for babies <6 months old), Visual Reinforcement Audiometry (for babies between 7 months and 2.5 years), Play Audiometry/ Performance test for toddlers between 2.5 years up to about 5 years).
Distraction testing - requires the child to turn to the sound when the sounds are being presented from behind the child on either side (right and left). This test is not carried out very often due to many limitations of the test.
Visual Reinforcement Audiometry - As the name suggests, the child's head-turns to the sounds are rewarded with a toy visually. The child is initially trained to associate the sound with a flashing toy. Once the child has learned to associate the 2, the child turns to look for the reward when he hears the noise. The turn is regarded as a response.
Performance/ Play audiometry - This is the closest to the type of testing done in adults. A repetitive game such as building blocks/ stacking shapes on to a stick/ filling pegs on a board is associated with the sounds. So, every time the child hears the sound, he puts a block/peg/shape. The play serves to be a response for the hearing test as well as a reward for the child.
The above procedures try to find the lowest sound level the baby can detect. Testing is often carried out by trained audiologists keeping in mind various variables involved with testing.
The most frequently used objective test is Auditory Brainstem Response (ABR). This is known by various other names such as BERA (Brainstem evoked response Audiometry). This test involves measuring responses from the nerves that are stimulation when the sounds pass thru the ear. For this test to be carried out successfully, it is preferred for the babies to be asleep. This is usually done under anaesthesia/ sedation in toddlers. Another such test records echoes from the ear. This is called OAEs (Oto-acoustic emissions).
Following may be some of the main symptoms:
- Children may show one or few of the following if they have hearing loss.
- Watch television or listen to radio at a high volume
- Misunderstanding what is being said to them/ answering questions inappropriately
- Difficulty in school
- Experiencing speech problems, has pronunciation errors
- Watching faces to understand what is being said to them
Hearing plays an important role in the development of speech and language in children. The extent of effect of hearing loss on the development of speech and language depends on the degree/ severity of hearing loss. Earlier detection of hearing loss is the key. The sooner the hearing loss is managed, less severe are the effects on speech and language development. It has been recommended world wide that children with hearing loss need to be managed (Eg. Fitted with hearing aids) before 6 months of age for the speech and language development to be normal/ near normal.
In certain countries like the UK and the US, newborn babies are screened for hearing loss using ABR and/or OAE. In India, screening is being carried out using behavioural tests. This essentially helps identify babies born with significant hearing loss.
If a baby fails the screening, they are often called for more detailed testing to accurately diagnose the severity and type of hearing loss.
The management of hearing loss is further decided by the audiologist. Some babies may have Fluid accumulation behind their ear drums. This usually resolves over time naturally. Some babies have sensorineural hearing loss and are fitted with hearing aids.
That essentially indicates that your child's hearing is normal/ near normal and you don't have to be concerned about his/her hearing. Babies who have been in the NICU for more than 5 days, babies with Jaundice requiring blood transfusion, babies born with facial abnormalities like cleft palate/lip, babies with certain genetic/ syndromic conditions may still be at risk of developing hearing loss. In some countries, such children are called back to see the audiologist for hearing screening at a particular age.
The procedures/tests for screening vary widely across countries, states and even within each state. You could contact your nearest audiological service/ audiologist for the locally followed procedures.