How do Khoekhoe click sounds use airflow differently from most English speech sounds?

Most English speech sounds are produced using a pulmonic airstream, which relies on the expiration of air from the lungs. In contrast, Khoekhoe and other Southern African languages that feature click sounds utilize a velaric airstream mechanism.1

This mechanism involves using the tongue to create a suction effect within the mouth. To produce these sounds, the back of the tongue typically contacts the soft palate while other parts of the tongue form a seal against the teeth or the alveolar ridge. By lowering the tongue, the speaker creates a partial vacuum; the distinct click noise is produced when this seal is released, allowing air to rush into the mouth cavity. While English speakers may use similar suction sounds as interjections—such as the sound of disapproval represented by "tsk, tsk"—these are not integrated into the language's consonant system as they are in Khoisan languages.21