Audiometry is an important method of otolaryngologic examination. The essence is the evaluation of perception of different types of sound and its possible failures.
Audiometry is of a great importance for the evaluation of hearing disorders. It not only confirms their presence, but it can determine what type of sound is the least perceived and which part of the auditory apparatus is affected.
The test does not require any special preparations. The patient should be placed in a soundproof room and the examiner may see his or her reactions through a glass window. The examined person wears special headphones and the examiner uses the audiometric device to emit sounds of certain frequency and volume. Both the frequency and volume change and the examined person gives a signal when the tone is heard. Each ear is tested separately. The result is a certain curve, which helps us to evaluate, which sounds (defined by their frequency and volume) the patient perceives.
Subsequently, the examiner can use a special device that is usually placed behind the ear. The device vibrates and emits tones that spreads through the skull bones to the auditory organ (cochlea) located within the temporal bone perception. This process is called “bone conduction of sound waves”.
The examination can determine, where is located the problem of hearing impairment. If the perception of sound from the headphones is significantly weakened, but the bone conduction is normal, it means that the problem is in the sound transmission to the sensory cells in the auditory organ (cochlea). The disruption may be either in the external ear canal, in the eardrum, or in the auditory ossicles of the middle ear.
The problem is either in the ear canal to the eardrum, or the car ossicles of the middle ear (“transmission disorder”). If the patient suffers from impaired hearing of both the tone in headphones and the bone-transmitted sound, then the problem is perception of the sound (either evaluation of the sound in cochlea, or the transfer of neuroelectric signal towards the brain) and we refer this situation to as the “perception disorder”. The picture below gives a much better understanding than any text.
Scheme - Disorders of transmission and perception in relation to anatomy of the auditory system
The examination has no specific disadvantages. However, specialized department equipped with adequate technology and skilled personnel is needed for correct implementation of the examination results.
The test is non-invasive, absolutely painless and does not expose the patient to any hazardous radiation. Moreover, it not only helps to detect the presence and severity of hearing loss, but it also determines where the hearing disorder originated, which can help in further diagnostic and therapeutic approach.