A mode of coherent mechanical energy transfer, usually referring to the transfer of energy from the sound source to the surrounding medium. Sound PROPAGATION, on the other hand, is the movement of SOUND WAVEs through a medium.
Compare: ABSORPTION, AMPLIFICATION, INCIDENCE, REFLECTION, RESONANCE, RESONATOR, SIMPLE SOUND SOURCE, SOUND PRESSURE, SYMPATHETIC VIBRATION, TRANSMISSION.
The flared horn of a trumpet or a LOUDSPEAKER can be called acoustic radiators. Each is designed such that a minimum of energy is wasted in the transmission process by being reflected back on itself, e.g. back into the tube of a trumpet. However, many objects not designed to radiate sound do so as a by-product of their internal processes, and often contribute to the AMBIENT NOISE LEVEL of the environment, such as is the case with all motors and machinery.