Phonetics: The Three Systems of Speech Production

Speech is a highly specialized motor performance, involving more than $100$ individual muscles.
The rate of speech production is faster than typing, texting, or any other form of human motor performance.
Producing speech requires an exceptionally high degree of coordination among multiple systems.
The speech process relies more heavily on motor fibers than any other human mechanical activity.
Communication through speech is only possible when the three primary systems of speech production—respiratory, laryngeal, and supralaryngeal—work together in a synchronized manner.

The respiratory system serves as the energy source for speech and consists of the lungs, rib cage, abdomen, and diaphragm.
Lungs: These are the primary organs where air is stored; they are protected by the rib cage.
Diaphragm: This is the large, flat muscle located below the lungs; it is the main muscle used for producing speech.
Respiration Process:
- Respiration is defined as the body's cyclic intake and exhalation of air.
- During preparation to breathe, the diaphragm drops.
- This movement causes the volume within the lungs to expand, facilitating the travel of air through the nose or mouth and through the larynx.
Direction of Airflow:
- Egressive Airflow: This is the flow of air out of the lungs. All English sounds are produced using egressive airflow.
- Ingressive Airflow: This refers to the inward flow of air.
Anatomical Components Involved in Respiration:
- Trachea (Windpipe): Serves as the primary air passageway.
- Bronchi and Bronchioles: Branching airways leading into the lungs.
- Alveoli: Tiny air sacs where gas exchange occurs.
- Pleura: Membranes surrounding the lungs.
- Ethmoid Sinuses: Air-filled spaces located in the bones around the nose.

Larynx (Voice Box): The larynx sits on top of the trachea and serves as the primary structure for phonation.
Primary Functions of the Larynx:
- Sound production.
- Safety mechanisms, such as the cough reflex to protect the airway.
- Pressure regulation.
Vocal Folds (Vocal Cords):
- These are flexible muscles attached to the walls of the pharynx that vibrate to produce sound.
- True Vocal Folds: The lower folds responsible for sound.
- Vestibular Folds (False Vocal Cords): Located above the true vocal folds.
- Glottis: The space between the vocal folds.
- Rate of Vibration: The speed at which vocal folds vibrate is known as the voice fundamental frequency, which is measured in Hertz ( $Hz$ ).
Phonation and Pitch:
- Vocal folds are typically open (abducted/apart) during regular breathing.
- During voicing, the vocal folds approximate (move together).
- Speech occurs on the exhalation of air as it passes through the vocal folds.
- Pitch is directly determined by vibration speed; faster vibration results in a higher pitch.
Supporting Structures:
- Epiglottis: A flap at the base of the tongue that covers the glottis during swallowing.
- Cartilages: Including the Cuneiform cartilage and Corniculate cartilage.

The supralaryngeal system is located above the larynx and includes the pharyngeal, oral, and nasal structures.
Pharynx: The primary resonating chamber for speech, situated on top of the esophagus.
Nasal Cavity:
- Chamber where speech resonates.
- Functions include filtering air and producing mucus.
- Anatomical features include the Frontal Sinus, Sphenoid Sinus, Nasopharynx, and Adenoid Pad.
- Turbinates (Superior, Middle, and Inferior): Structures that help regulate airflow.
- Eustachian tube orifice and Fossa of Rosenmuller are also located in this region.
Oral Cavity:
- Includes the hard palate, soft palate (velum), uvula, tonsils, gingiva (gums), and buccal mucosa (lining of the lips and cheeks).
- Hard Palate: The bony roof of the mouth and a vocal resonator.
- Soft Palate (Velum): An extension of the hard palate that helps control airflow from the lungs to the mouth and nasal cavity; it is essential for both speech and swallowing.
- Uvula: A small structure hanging from the middle of the soft palate.
Velopharyngeal Closure:
- The direction of sound (oral vs. nasal) is determined by the position of the velum.
- During closure, the soft palate moves superiorly and posteriorly.
- Simultaneously, the side pharyngeal walls move medially, and the posterior pharyngeal wall moves anteriorly.

Jaw (Mandible): Connected to the skull via the temporomandibular joint (TMJ).
Tongue: A primary articulator with distinct regions:
- Body
- Tip
- Blade
- Dorsum
- Root
Lips: Involved in the shaping of speech sounds.
Teeth: Serve as points of contact or barriers for airflow during articulation.
Additional structures in the oral cavity include the retromolar trigone and the floor of the mouth.