Sound producing device and valve

A sound producing device, comprising:

• at least one air pulse generating element, each of the at least one air pulse generating element comprising:
• an air chamber;
• a membrane disposed in the air chamber and having a plurality side edges;
• a first air entrance disposed at a side of the membrane in a first direction and adjacent to one of the side edges of the membrane;
• and
• a first valve disposed between the first air entrance and the membrane;
• and
• a control unit configured to generate at least one driving signal, wherein the driving signal controls a movement of the membrane of the air pulse generating element, such that the air pulse generating element generates an air pulse in response to the corresponding driving signal;
• wherein during an operation of the sound producing device, a first airflow corresponding to the air pulse flows into or flows out of the air chamber through the first air entrance, the first airflow passes through the first air entrance substantially along a direction parallel to the first direction, the first direction is substantially perpendicular to a direction of the movement of the membrane, and the first valve is configured to control a path of the first airflow.