Sound amplification by stimulated emission of radiation phenomenon, known as the Larsen effect, is the result of a positive feedback. In general, every oscillator consists of three main parts. These are the power source or pump, the amplifier and the positive feedback leading to the output. The corresponding parts in a SASER device are the excitation or pumping mechanism, the active (amplifying) medium, and the feedback leading to acoustic radiation. Pumping can be performed, for instance, with an alternating electric field or with some mechanical vibrations of resonators. The active medium should be a material in which sound amplification can be induced. An example of a feedback
A Sense of Direction A Sense of Direction A Sense of Direction is an album led by vibraphonist and composer Walt Dickerson recorded in 1961 and released on the New Jazz label. AllMusic awarded the album 4½ stars with its review by Steve Huey stating, "If it's a shade less challenging and inventive than "This Is Walt Dickerson!", "A Sense of Direction" compensates by making Dickerson's innovations more accessible and inviting". Down Beat reviewer Pete Welding wrote "if it is only slightly less adventurous than his initial recording, it is still an ardent collection -- primarily of ballads -- treated with unflagging invention and