Audio feedback is a phenomenon that occurs when sound produced by an audio system, such as a microphone or loudspeaker, is picked up again by the same system and re-amplified. This results in a loop of sound, causing a howling or screeching noise. It can occur when a microphone is placed too close to its amplifier or speaker, or if there are any defects in the audio equipment. Audio feedback is typically experienced during live performances, where the performer's voice or instrument signal is being reinforced through a PA system and picked up by nearby microphones, creating an oscillation loop.