What is the role of air pressure in the respiratory process according to speech science?

Air pressure plays a critical role in the respiratory process by influencing the flow of air into and out of the lungs. Inhaling and exhaling are fundamentally dependent on pressure changes within the thoracic cavity, which are created by the contraction and relaxation of the diaphragm and intercostal muscles. When the diaphragm contracts, it expands the volume of the thoracic cavity, thereby decreasing the air pressure inside the lungs compared to the outside atmosphere, causing air to flow in. Conversely, during exhalation, the diaphragm relaxes, the volume of the thoracic cavity decreases, and the air pressure within the lungs becomes higher than the atmospheric pressure, which pushes air out.

This process of airflow driven by differential air pressure is essential not only for gas exchange but also for speech production, as it provides the necessary airflow for generating sound. Understanding the mechanics of how air pressure functions in respiration is fundamental in speech science, as it directly impacts vocalization and the ability to produce speech sounds.