Sensory impairments

(B- Hearing impairment)

The audible sound is a signal that contains a tone or several tones produced by a certain organ of an organism aiming at communicating with another organism (of the same kind or of another kind) and by which it expresses what it wants to say or do. The sensation caused by these frequencies is called hearing.

Physically, sound is a frequency resulting from the vibration of a body and it travels only through a physical medium (solid – liquid – gas) and does not spread in a vacuum.

Sound waves: waves of which frequency is between 20 Hz i.e. (20 vibrations per second), and 20 thousand Hz, and only this range of sound waves can be heard by humans (Hz is the unit of frequency measurement and is equal to one vibration per second).

Ultrasound: Ultrasound waves with a frequency of more than 20,000 Hz that cannot be detected by the human ear.

Infrasound: waves with a frequency of less than 20 Hz that are not detected by the human ear.

Hearing Impairment

It is a hearing deficiency to the extent that prevents the auditory system from performing its function. This type of disabilities leads to social isolation and limits the affected persons from using their abilities. The environment often plays a key role in the occurrence of such disability.

It is an impairment that prevents the individual from hearing spoken speech with or without hearing aids, and it includes 2 categories: (the deaf) and (the hard of hearing).

A deaf person is:

-An individual who is unable to respond in a way that indicates an understanding of audible speech.

-An individual who suffers from a defect in the auditory system that prevents him from acquiring language by normal methods, due to the loss of the ability to hear before learning to speak or as soon as they learn to speak as a result of a malfunction.

There are those who define the deaf as a child who has lost his hearing ability in the first three years of his life, which leads to his failure to acquire language.

Classification of hearing impairment:

The classification and types of hearing impairment varies according to the criteria of the classification:

First: The first criterion is based on the age at which the injury occurred, and is divided into:

1 – Impairment since birth: The individual is hard of hearing from the moment he was born.

2- Pre-Language Learning impairment: It occurs before the age of three (before language learning and acquisition) – they do not speak because they have not heard the language.

3- Post-Language Learning impairment: It occurs after speech and language development.

4- Acquired impairment: It occurs after birth, with a loss of the language abilities that were already developed, but no special rehabilitation services were provided to them.

Second: Severity of hearing loss criterion, it is divided into:

1 – A very simple impairment: in which it is difficult for the individual to hear faint or far sounds, or distinguish some sounds. Hearing aids and therapeutic programs can be used in these cases. (Hearing loss is between (27-40) decibels).

2 – Simple impairment The individual can hear and understand the speech at a distance of 3-5 meters from the source The affected person could explains 50% of discussions if the voices are faint or far away, but accompanied by deviations in pronunciation or speech, therefore; they need special education programs. (Hearing loss is between (41-55) decibels).

3- Moderate impairment: in which the individual does not understand the conversation unless it is aloud. It is hard for the affected persons to engage in group discussions because their verbal dictionary is limited, with the presence of language disorders, which requires joining a special class and using hearing aids. (Hearing loss is between (56-70) decibels).

4- Severe impairment: in which the individual cannot hear even loud sounds, with disorders of speech and language, which prevents the development of the language of the child if it happened in the first year, here the child needs a special school for the hearing disabled persons  to learn and train on the hearing and lip reading as he depends on the sense of sight. There is a need for a stethoscope in this case. (Hearing loss is between (71-90) decibels)

A decibel dB is a unit, used to measure the ratio of two values, and in audio science the ratio of two sound intensities. (unit of sound intensity)

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