The term 'pressure differential' refers to:

• A. Measurement of airflow
• B. Change in pressure across containers
• C. Volume measurement
• D. Force exerted by muscles

Answer: (B)

The term "pressure differential" specifically refers to the change in pressure between two points or across two different areas. This concept is crucial in various fields, including speech science, because it relates to how air pressure differences drive airflow, which is essential for sound production in speech.

In the context of speaking, when the pressure in the lungs is higher than the atmospheric pressure outside the body, air is pushed out, allowing phonation to occur. Understanding this difference in pressure helps in comprehending how sounds are generated and articulated.

While airflow measurement, volume measurement, and muscle force are relevant to the production of speech, they do not directly encapsulate the concept of pressure differential, which concerns itself specifically with the variation in pressure. Thus, the correct choice highlights the fundamental principle that drives many processes, including those involved in human speech.