Acoustics: Sound Fields, Transducers and Vibration, 2nd Edition

13.8. Radiation from a resilient circular disk without a baffle [17]

The resilient circular disk in free space is the simplest dipole planar source and the dipole complement of the rigid circular piston in an infinite baffle. It can be used as an approximate model for unbaffled loudspeakers of the electrostatic or planar magnetic type, in which it is assumed that a perfectly uniform driving pressure is applied to a very light flexible membrane diaphragm in free space. Because of the dipole nature of the source, there is zero pressure in the plane of the disk extending beyond its perimeter. Walker [18] pointed out that such a source is acoustically transparent, in that it does not disturb the field around it, and used this idealized model to ...