Generality
Audiometry is a method by which it is possible to perform an assessment of the hearing ability of an individual.
The diagnosis of any hypoacusis and / or deafness, on the other hand, lies solely and exclusively with the otolaryngologist and not with the audiometrist.
The audiometric examination must be carried out in a place where the patient cannot be distracted by other "background" noises that may be present in the surrounding environment. For this reason, this type of examination is usually conducted within the so-called "audiometric cabin" which is able to acoustically isolate the patient.
In light of what has just been said, it is clear what the importance of audiometry is in identifying important hearing disorders, whose progression - if identified promptly - could be effectively stopped or slowed down.
However, the results of the audiometry must always be interpreted according to the age of the subject. In fact, it is good to remember that with advancing age - due to the degeneration of auditory structures related to natural aging processes - a certain level of hearing loss can also be considered normal (in these cases, we usually speak of presbycusis) .
Basically, we can say that there are three different types of audiometry: tonal audiometry, speech audiometry and high frequency audiometry . The main characteristics of these different forms of audiometry will be briefly described below.
Tonal Audiometry
Tonal audiometry is a particular type of audiometry that allows you to determine a person's auditory sensitivity to sounds.
This examination is conducted in a silent environment, with the aid of a special instrument (audiometer) capable of generating pure sounds, with a single frequency of vibration.
Stimulation can take place in two different ways:
- By air, that is with the use of headphones that the patient must wear and through which the sound stimulus is sent. Therefore, the sound to reach the inner ear must first pass through the outer ear and the middle ear.
- By bone ; in this case, instead, the pure sound is transmitted to the cochlea (therefore to the acoustic nerve) through the vibration of the mastoid process of the ear to be examined.
Furthermore, tonal audiometry can be of two types:
- Supraliminal tonal audiometry : method that allows to determine the thresholds for comfortable listening and the patient's discomfort. In this case, the audiometric examination will be performed using sound stimuli of increasing intensity.
- Liminal tonal audiometry : this method, on the other hand, aims to determine the absolute audiometric threshold of a patient with regard to sound stimuli. Unlike what happens with the supra-tonal tonal audiometry, in this case the sound stimuli do not vary in intensity.
Generally, the exam in question begins by testing the conduct of acute frequencies (from 2, 048 Hz up to 8, 192 Hz) and then serious frequencies (from 512 Hz to 128 Hz). During the exam, the patient must raise his hand or push a button to confirm that he has heard the sound.
The data collected by the audiometry gives rise to a tonal audiogram that will be analyzed by the audiometrist technician.
Vocal Audiometry
Speech audiometry aims to identify the patient's ability to understand words.
Also in this case, the exam is conducted inside the audiometric booth. Local stimuli can be sent to the patient in free field or with headphones.
The exam is based on listening to the patient of different words, which can be spoken by the examiner himself, or can be recorded. The patient's task will be to repeat all the words he was able to understand.
Generally, the exam begins by making the patient listen to a certain number of words with a high intensity of stimulation, in order to evaluate the quantity of words included. Then the patient will have to listen to a series of other words with different stimulation intensity, in order to determine which words have been understood and to what intensity. These data will then be converted into percentages and inserted into a graphic ( vocal audiogram ) which also in this case will be interpreted by the audiometer.
High Frequency Audiometry
High frequency audiometry, as can be guessed from its very name, aims to determine the patient's audiometric threshold for pure high frequency sounds, more precisely those with frequencies above 8, 192 Hz.
Generally, in this type of audiometry, the range of sound frequencies analyzed ranges from 8, 000 to 20, 000 Hz.
This particular type of audiometry is usually carried out to detect in an early manner possible cochlear oto-toxicities that may have been caused by exposure to toxic substances, or by the use of certain types of drugs, such as, for example, cisplatin ( an anticancer) or aminoglycosides (antibiotic drugs).
