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 Boy, a Girl and a Bike A Boy, a Girl and a Bike A Boy, a Girl and a Bike is a 1949 British romantic comedy film directed by Ralph Smart and starring John McCallum, Honor Blackman and Patrick Holt. The film's art direction was by George Provis. The film concerns the romantic escapades and adventures of a Yorkshire cycling club. Young couple Sue (Honor Blackman) and Sam (Patrick Holt) are members of a Yorkshire cycling club, the ‘Wakeford Wheelers’. Romantic complications ensue when wealthy David (John McCallum) becomes smitten with Sue, and joins the club to pursue her, much to Sam's dismay. The "Radio Times"