The term audiometer, derived from the Latin audio (to hear) and from the Greek metron (measurement), represents a medical instrument used in audiometry to measure the hearing capacities of individuals. It is also called acoumeter.

The audiometer allows hearing tests to be performed by specifying the audible limit of the sounds that can be perceived by human hearing under the conditions of the test. Its function is to detect and characterize hearing disorders in patients.

Why take a hearing test

Hearing is one of our senses the most “attacked” by the environment. Most of us today live in an increasingly noisy environment, whether on the streets, at work, at play, and even at home. Performing a regular hearing assessment is therefore particularly recommended, especially in babies, young children, or adolescents in whom the excessive use of headphones can have serious consequences. Check-ups allow hearing problems to be detected early and remedied as quickly as possible. In adults showing signs of hearing loss, check-ups help determine the nature of the deafness and the area concerned.

Composition

Audiometers are made up of different elements:

• a central unit controlled by the manipulator, which is used to send the various sounds to the patient and to record his responses in return;
• a headset to be placed on the patient’s ears, each earpiece functioning independently;
• a remote control entrusted to the patient to send the responses;
• cables to connect the different elements together.

Audiometers can be fixed or portable, manual or automatic controlled by a computer equipped with suitable software.

The hearing test is a quick, painless and non-invasive examination. It is intended for adults as well as the elderly or children. It can be performed by an ENT specialist, an occupational doctor, a school doctor or a pediatrician.

Two types of measurement are performed: tonal audiometry and voice audiometry.

Tonal audiometry: hearing

The professional makes the patient hear several pure tones. Each sound is characterized by two parameters:

• The frequency: it is the pitch of the sound. A low frequency corresponds to a low sound, then the more you increase the frequency, the higher the sound becomes;
• Intensity: this is the volume of sound. The higher the intensity, the louder the sound.

For each sound tested, the hearing threshold is determined: it is the minimum intensity at which sound is perceived for a given frequency. A series of measurements are obtained which allow the curve of the audiogram to be drawn.

Speech audiometry: understanding

After the tone audiometry, the professional performs speech audiometry to determine to what extent hearing loss affects speech understanding. It is therefore not the perception of sounds that is evaluated this time, but the comprehension of words of 1 to 2 syllables which are diffused at different intensities. This test is used to assess the intelligibility threshold words and draw the corresponding audiogram.

Reading the tonal audiogram

An audiogram is established for each ear. A series of measurements corresponding to the set of hearing thresholds determined for each sound makes it possible to draw a curve. This is shown on a graph, the horizontal axis of which corresponds to the frequencies and the vertical axis to the intensities.

The scale of the frequencies tested extends from 20 Hz (Hertz) to 20 Hz, and the scale of the intensities from 000 dB (decibel) to 0 dB. To represent the values ​​of sound intensities, we can give some examples:

• 30 dB: chuchotement;
• 60 dB: discussion aloud;
• 90 dB: urban traffic;
• 110 dB: thunderclap;
• 120 dB: rock music concert;
• 140 dB: plane taking off.

Interpretation of audiograms

Each curve obtained is compared to a normal hearing curve. Any difference between the two curves attests to a hearing loss in the patient and makes it possible to know the level:

• from 20 to 40 dB: slight deafness;
• from 40 to 70 dB: moderate deafness;
• 70 to 90 dB: severe deafness;
• more than 90 dB: profound deafness;
• not measurable: total deafness.

Depending on the area of ​​the ear that is affected, we can define the type of deafness:

• conductive hearing loss affects the middle and outer ear. It is transient and is caused by inflammation, the presence of an earwax plug, etc. ;
• sensorineural hearing loss affects the deep ear and is irreversible;
• mixed deafness.

The stages of operation

Despite their apparent simplicity of realization, hearing tests have the particularity of being subjective.

They must therefore be carefully prepared to be reproducible and above all, they require the full cooperation of the patient:

• the patient is installed in a calm environment, ideally in an acoustic booth;
• the sounds are first of all diffused by air (via headphones or speakers) then, in the event of hearing loss, via the bone thanks to a vibrator directly applied to the skull;
• the patient has a pear which he squeezes to indicate that he has heard the sound;
• for the voice test, words of 1 to 2 syllables are broadcast through the air and the patient has to repeat them.

Precautions to take

To make sure that the hearing loss is not due to ear occlusion by an earwax plug or due to inflammation, it is advisable to perform an otoscopy beforehand.

In certain cases, it is recommended to carry out a preliminary acumetry in order to “roughen” the ground. This exam consists of various tests: loud whisper test, obstruction test, tuning fork tests.

For babies and children under 4 years of age, in whom the use of an audiometer is impossible, the screenings are carried out with the Moatti test (set of 4 moo boxes) and the Boel test (device reproducing sounds of bells).

The criteria for choosing well

• Size and weight: for outpatient use, lightweight audiometers that fit in the hand, Colson type, are preferred, while for static use, larger audiometers, possibly coupled to computers and offering more functions will be privileged.
• Power supply: mains, rechargeable battery or batteries.
• Functions: all audiometer models share the same basic functions, but the most advanced models offer more capabilities: wider spectrum of frequencies and sound volumes with smaller gaps between two measurements, more intuitive reading screen, etc.
• The accessories: more or less comfortable audiometric headphones, response bulb, transport pouch, cables, etc.
• The price: the price range oscillates between 500 to 10 euros.
• Standards: ensure CE marking and warranty.