Definitions
What is an acoustic load?
Vbration of a membrane is influenced by presence of a fluid in contact with its faces.
For a slow movement, the fluid is driven by the diaphragm and moves with it, unless near walls opposing to this movement. If the vibration is very rapid, the inertia of the fluid prevents it from perfectly following the motion of the membrane, and it also undergoes a compression.
The term "acoustic load" refers to the reaction exerted by the fluid on the membrane, whose behavior is so modified.
The acoustic loads studied later in this course are:
acoustic radiation (effect of the air in front of a vibrating piston mounted on a screen),
sealed enclosure (sealed volume where the fluid is compressed),
vented enclosure (Helmholtz resonator).
