1 To comply with Department of Defense changes to common access cards, and to comply with Homeland Security Presidential Directive 12, the Fort Knox One Stop In-processing Center has recently started implementing changes to the CAC issuing process.
acoustics - the study of the physical properties of sound. acoustic radiation pressure - (acoustics) the pressure exerted on a surface normal to the direction of propagation of a sound wave. physical science, physics - the physical properties, phenomena, and laws of something; he studied the physics of radiation. harmonics - the study of musical sound.
any of various devices, usually electronic, by which speech, music, etc., can be intensified and made audible throughout a room, hall, or the like. 2. Audio. a device for transforming electric signals into audible sound, most frequently used to reproduce speech and music. speaker (def 4).