Speech and communication disorders
Speech and communication disorders are impairments that affect the ability to communicate, comprehend, and use verbal spoken and written languages, and also other symbol systems, called nonverbal languages (e.g., visual language, body language, etc.). Their severity can range from a few errors, for instance, in uttering speech sounds or words, to a total loss of the ability to effectively communicate. This can affect even subjects' developing of thoughts, which is a prerequisite for the enacting of behaviours and social interaction.
In communication, the functions and skills of voice, speech, and language are deeply related. In fact, those subjects who are affected by a congenital deafness, and experience therefore a delay in acquiring and mastering verbal language, may have trouble not only in the discrimination of similar sounds (in decoding as well as in producing oral messages), but also in the distinction of related concepts.
Voice is the sound produced by the airflow coming from the chest: during exhalation, the air held in the lungs is gradually released and travels to the trachea and the larynx, where the vocal cords (two bands of muscular tissue) are located.
When a subject talks, laughs, sings, or cries (as well as when an infant babbles or coos), his or her vocal cords are brought closer together (so that the air from the lungs is forced between them) and vibrate, giving origin to a sound; this process is called phonation. Therefore, voice production involves respiration and phonation and requires the precise coordination of many specific muscles.
Speech is originated through a complex process, coordinated and controlled by the brain, through the nervous system. The sound originated by the vocal cords can be accurately modulated as regards pitch, volume, timbre, rhythm, and so forth, by means of well-defined muscle movements, which involve...