Speech production: It’s amazing we get it right!
Talking is something that is fairly effortless for most people, but have you ever wondered how your speech is actually produced? Speech can be produced at rates of up to six to nine syllables (or 20 to 30 phonetic segments) per second. This is faster than any other motor behavior that humans can do. Furthermore, speech production requires more motor fibers than any other human mechanical activity (Fink, 1986). Clearly, the process of speech production is complex and there are several different body sub-systems that are involved in speech production, including the respiratory, phonatory, and articulatory subsystems. After an intended message has been formed in your mind, these three physiological components are essential in order to transform your desired communication into audible speech.
- Respiration: In order for speech sounds to be produced, air needs to be inhaled into the lungs to supply “energy” for speaking. When you inhale, your ribcage expands and your diaphragm lowers. This increases the volume of the thoracic cavity and subsequently your lungs, in turn decreasing the air pressure in your lungs. This inhaled breath builds up beneath your vocal folds to create tracheal pressure. At this point, the air can be thought of as the potential energy for speech.
- Phonation: When the tracheal pressure reaches a certain point, the vocal folds are forced open and the air is released. As the air flows through the larynx, the vocal folds vibrate, phonation occurs which transforms the potential energy into sound. The myo-elastic aerodynamic therapy explains the process of phonation. Briefly, as you exhale and push air through your glottis, the vocal folds are “blown” apart. Next, the pressure surrounding them drops and they are “sucked” back together. This pressure exchange continues and the process is repeated, causing your vocal folds to open and close at high speeds. While the vocal folds are vibrating, the muscles surrounding and supporting them are controlling your voice frequency, or pitch.
- Articulation: The third step in producing speech is articulation, or the modification of the voice energy to create speech sounds. In order for speech to be effective, proper articulation is essential. Different sounds can be produced by changing the shape of your vocal tract by means of your articulators. Your lower lip and tongue are active articulators which come into contact with your upper lip, teeth, alveolar ridge, hard palate, soft palate, uvula and pharynx wall to produce a variety of speech sounds. By modifying these areas to produce different sounds, clear speech will be articulated.
This process describes normal, non-disordered speech production. However, neurodegeneration or injury to any of these sub-systems, or to the brain or spinal cord (which control the movements of these subsystems) can have an adverse effect on any of the aforementioned steps of speech production. Speech-Language Pathologists are trained in the evaluation and treatment of speech disorders, and can help rehabilitate affected individuals through various therapeutic methods.