What is a pure-tone audiometry test?
Pure-tone audiometry is a subjective test used to assess a person’s hearing ability.
It evaluates the auditory pathway both at the peripheral and central levels.
What is the purpose of audiometry?
The main purpose of pure-tone audiometry is to measure the minimum sound intensity (hearing threshold) a person needs to hear at each of the different frequencies tested.
Audiometry measures sound intensity in decibels (dB) and frequency in hertz (Hz).
In audiometry, the usual hearing range tested is between 125 and 8000 Hz, and intensities between 0 and 110 dB.
Degrees of hearing loss in pure-tone audiometry:
The results of the audiometry are expressed as the average hearing threshold, called the Pure Tone Average (PTA).
According to the PTA determined by pure-tone audiometry, hearing is classified as follows:
- Normal hearing: between 0 and 30 dB. A hearing threshold up to 30 dB is considered within normal limits.
- Mild hearing loss: between 31 and 40 dB. Mild hearing loss increases listening effort and makes it harder to filter out background noise, potentially leading to lack of attention.
- Moderate hearing loss: between 41 and 70 dB. Moderate hearing loss makes conversations harder to understand, which may affect language development.
- Severe hearing loss: between 70 and 90 dB. Patients with severe hearing loss may have difficulties interacting with others, which can lead to isolation and low self-esteem.
- Profound hearing loss: more than 90 dB. Patients with profound deafness develop progressive deterioration of speech and language.
Types of hearing loss
Pure-tone audiometry can assess hearing thresholds both through air conduction and bone conduction. This allows us to determine the degree of hearing and the type of hearing loss a patient has.
The types of hearing loss identified in pure-tone audiometry are:
- Conductive hearing loss: due to problems in the outer ear, such as earwax blockage, or in the middle ear, such as acute otitis media, serous otitis, or otosclerosis.
- Sensorineural hearing loss: secondary to problems in the cochlea, the auditory nerve, or the central auditory pathway. Examples include presbycusis, Ménière’s disease, and acoustic trauma from noise exposure, among others.
- Mixed hearing loss: combines both conductive and sensorineural components.
What is an audiogram?
The results obtained in the audiometry test are plotted on a chart (audiogram) that represents the hearing curves according to the measured hearing threshold for each frequency.
Who cannot undergo pure-tone audiometry?Pure-tone audiometry can be performed on any person capable of cooperating.
In the case of very young children under the age of 3 or 4, patients with cognitive disabilities, or when there is suspicion of unwillingness to cooperate for any reason, it is advisable to use another test that does not require the patient’s cooperation.
How is pure-tone audiometry performed?
Ideally, pure-tone audiometry should be carried out in a soundproof booth, using headphones, loudspeakers, and a bone conduction oscillator.
The patient is asked to enter the booth, take a seat, and after a brief explanation of the procedure, headphones are placed on them. They are instructed to press a button—or alternatively raise a hand—whenever they hear a faint, intermittent sound. This is done separately for each ear. Finally, if necessary, the same procedure is repeated, but the sound is delivered through a bone conduction oscillator placed on the mastoid bone.