Central and lateral airflow

Central airflow is when the air flows down the middle of the vocal tract. If you say the sound [s], hold the articulation and then suck air in, you should feel that it goes cold and dry down the middle of your tongue and Central airflow is when the air flows down the middle of the vocal tract. If you say the sound [s], hold the articulation and then suck air in, you should feel that it goes cold and dry down the middle of your tongue and the middle of the roof of your mouth. The cold and dry patches will be more or less symmetrical on each side of your mouth. All languages have sounds with central airflow

Lateral airflow is when the air flows down one or both sides of the vocal tract. If you say the sound [l], hold the articulation and then suck air in, you should feel this time that it goes cold and dry down one or both sides of the mouth, but not down the middle. The sides of the tongue are lowered, and the air passes out between the back teeth.

In theory, lateral airflow can be produced at the lips too: to do this, keep the sides of the lips together and try saying something like ‘Pepé bought a pencil’. It will both sound and look strange. It is probably not a surprise that no language has lateral airflow caused by constricting the lips at one side, and this combination is blocked out in the chart of the International Phonetic Association.