It is pronoumced by raising the tongue tip against the upper teethridge to block the air and then putting it down to release the air.

下唇和上齿，成一条狭缝，气流狭缝中磨擦而出。

It is pronounced by raising the tongue tip against the upper teethridge to block the air and then putting it down to release the air.

住上齿龈，阴住气流，然后移下，放出气流。