1. The return of a portion of the output, or processed portion of the output, of a (usually active) device to the input. (188 ) Note 1: The feedback signal will have a certain magnitude and phase relationship relative to the output signal or the input signal. This relationship can be used to influence the behavior, such as the gain and stability, of the overall circuit. Note 2: If the feedback is regenerative (additive), it is called "positive feedback," which increases gain and distortion, and decreases linearity and stability. Note 3: If the feedback is degenerative (subtractive), it is called "negative feedback," which reduces the gain and distortion, and increases linearity and stability. Note 4: Feedback may occur inadvertently, and be detrimental. 2. Information returned as a response to an originating source.
In acoustics, the undesirable leakage of audio from loudspeakers back into a microphone, resulting in a loud squeal or howling sound, or in less severe cases, a hollow ringing sound quality or whistles.