Egressive pulmonic airflow is the normal mechanism for producing speech sounds in all languages. In languages as diverse as Swahili and English, Chinese and Greek, we find no other mechanism at all. A few languages make use of another airstream mechanism, but these always play a fairly minor role in the production of a few vowels or consonants.
The respiratory cycle
At rest, we tend to breathe in and out in even cycles of about 2-3 seconds each. If we breathed like this to speak, then we could only talk half the time, and we’d be limited to short sentences on each out-breath half of the cycle.
For speaking though, we switch to a specialised breathing pattern that maximises the outflow time, and minimises the inflow time. With short sharp inhalation (of about half a second), and long slow controlled exhalation (5 – 15 seconds is normal), we can be very efficient speakers and talk most of the time (and some of us do!).
Play the animation to see the diaphragm contract to deliver egressive airflow.