Audiometry

Alternative names

Audiometric test, audiography, audiology.

Definition

Audiometry is a test that aims to study hearing disorders. To understand the audiometric study it is necessary to know the functioning of the auditory system.

The sounds in our environment are a set of sound waves or vibrations that circulate mainly through the air environment, although they can also travel through solid or liquid media. The main characteristics of these vibrations are frequency and intensity. The frequency corresponds to the number of vibrations that occur in a given time (cycles / second or hertz). Intensity could be understood as the strength of the sound wave and its unit of measurement is the decibel (dB). The human ear is capable of distinguishing and identifying multiple sounds thanks to the differentiating characteristics of the various sound waves.

The ear is made up of two main anatomical structures: the conduction apparatus and the perception apparatus. The first is responsible for transmitting acoustic vibrations to the inner ear. The second constitutes the sensory organ and is located in the inner ear.

Airborne sound waves pass through the outer ear and middle ear to the inner ear. There, physical stimulation in the form of sound waves is translated into a nerve impulse by internal and complex structures such as the cochlea. The generated nerve impulse will reach specific regions of the brain, where the perceived acoustic wave will be given meaning.

Audiometry is a test that numbers hearing loss and determines its magnitude in relation to perceived acoustic vibrations. The airway, that is, the ability to hear sounds transmitted through the air, and the bone pathway, which is the ability to perceive sound through the bones of the head, are explored. The results of an audiometry are presented graphically. This graph shows how much the patient is able to hear in decibels at different frequencies that are measured in Hertz (Hz). In a conventional audiometry, sounds ranging from 250 Hz to 40,000 Hz are presented. These frequencies are those of the spoken voice and therefore are the most important to evaluate.

How is the study done?

First, the patient must enter a soundproof booth and put on headphones. Both ears are examined independently. The examiner will then present you with a series of sounds to which you must respond by raising your hand. These sounds will decrease in intensity until they become inaudible. This determines the "hearing threshold", that is, how far the patient is able to hear. This same task will be repeated several times with sounds at different frequencies, with which at the end of the test it will be known to what extent the patient is able to hear each sound evaluated. For the exploration of the bone route, a vibrator is applied behind the ear, in the region known as the mastoids. The approximate duration of the test is about 15 minutes. After it, the audiogram or graphic representation of the patient's hearing capacity is obtained.

Preparation for the study

The examination does not require prior preparation.

What does it feel like during and after the study?

It is a common and comfortable examination for the patient, since it does not involve risks or discomfort during its performance.

Exceptionally, in patients with an auditory disorder known as hyperacusis, the sound stimulus can be annoying at certain frequencies or intensities.

Study risks

There are no risks.

Contraindications of the study.

There are no contraindications.

Reasons why the study is carried out

It is a useful examination for the diagnosis of hearing loss. Its use is also common in occupational health checks for workers exposed to potentially harmful sounds. Comparison of the results obtained in the airway and bone conduction tests makes it possible to locate which part of the auditory mechanism is responsible for the deficit. If the loss is due to problems in the middle ear, it is called conductive hearing loss; If, on the other hand, it is a problem of the inner ear, then we will speak of sensorineural or perceptual hearing loss.

Thanks to audiometry it is also possible to determine the degree of hearing loss, as well as to carry out periodic checks to assess its progression. From these audiograms the following types of hearing can be established:

• Normal hearing (up to 25 dB). There are no problems hearing and understanding.
• Medium hearing loss (26-45 dB). They have some difficulty hearing and understanding someone who is speaking to them at a distance or speaking a little quietly. Listening to conversations with noisy backgrounds is difficult for them.
• Moderate hearing loss (46-65 dB). There are difficulties understanding conversations. Trying to listen to conversations in noisy backgrounds is extremely difficult.
• Severe hearing loss (66-85 dB). They have a hard time listening in all situations.
• Profound hearing loss (more than 85 dB). They do not hear even if they are yelled at or there are very loud noises around them.

Among the most common causes of hearing loss are presbycusis or hearing impairment caused by age, acoustic trauma, chronic ear infections, certain inherited disorders, and some medications (antibiotics, diuretics, and salicylates, among others).