To assess the true extent of the hearing loss problem it is necessary to contact an audiologist.

In some countries your local general practitioner can refer you.
He or she will evaluate your hearing and determine the degree of hearing impairment that you have.

Hearing test

A hearing test ascertains how well a person hears, commonly referred to as "hearing sensitivity":

Using headphones you listen to a series of pure tones (simple sound) from 125 Hz to 8000 Hz (this is the frequency range where the ear is most sensitive, i.e. hears the best, in addition to being the most important pitches for speech comprehension) You indicate - by raising a hand or pressing a button - whether or not you actually heard the sound The sound decreases in intensity level so that the audiologist can determine the levels at which you can just detect the sound (thresholds)

The results of the test are plotted on an audiogram. Along the bottom the frequencies are represented and up the side the intensity level in dB HL is shown. Crosses are typically used to represent the left ear and circles normally indicate the results for the right ear.

Note that the decibel scale is logarithmic: it means that
A sound 10 dB greater than another is 10 times more intense.
A sound 20 dB greater than another is not 20, but 100 times more intense (10x10).
A sound 30 dB greater than another is not 30, but 1000 times more intense (10x10x10).

Behavioral testing

Behavioural testing is an approach that requires a response by the child to a sound. The response used depends on the developmental stage of the child. The child should always be awake and alert.

A test stimuli is delivered through earphones or speakers and the child responds by showing awareness of sounds.
For the first few months of a baby's life, behavioural testing consists of trained observation of subtle changes in an infant's activity (e.g. eye or head movements) when sound is presented (Behavioural Observation).
In later infancy, up to about age two, children are able and willing to turn to the sound and are reinforced by a flashing light and/or moving toy whenever they respond (Visual Reinforcement Audiometry).
Usually between the ages of two and three years old, most children can be taught to perform a conditioned play task, such as putting a block in a box or a peg in a hole, whenever they hear the sound (Play Audiometry).
Older children (usually aged five and above) and adults are able to raise their hand or press a button each time they hear the sound.

Objective tests

Objective tests do not require the child or adult to make a response. The ones described below can be carried out if the individual is asleep or awake.

Auditory Brainstem Response Testing (ABR): can be performed while an individual is asleep or resting quietly and can provide reliable threshold information for frequencies up to 2kHz . It is often used for those unable to perform behavioural tests, such as infants under the age of 6 months. Electrical impulses from the auditory nerve and brainstem are recorded in response to click stimuli presented through earphones.

Transient Otoacoustic Emission (TEOAE) testing can also be measured during sleep and assesses the response of the outer hair cells to transient click stimuli presented to each ear. Outer hair cells are usually the ones to be damaged first when there is a hearing loss so this can be a very good screening tool for assessing cochlear damage. If there were complete outer hair cell damage, that would typically lead to a hearing loss of approximately 60dB HL. This is a very quick test and is often used for neonatal hearing screening.

Immittance Audiometry (tympanometry and acoustic stapedial reflex testing) in conjunction with other tests can be a useful diagnostic tool. The compliance and pressure of the middle ear are assessed. This can give an indication as to whether there is a middle ear hearing disorder and also the type of middle ear problem there might be. Stapedial reflex responses can also be measured, this is particularly useful for determining if the hearing loss is neural in nature.