Audio feedback
As Acoustic feedback or feedback refers to an audio effect, in which the electrical signal generator between a dependent of a sound source (such as a microphone, electric guitar or electric bass) and connected to a powered with this signal audio amplifier speakers a feedback is established. The effect can already be triggered by the noise and otherwise arises when the diaphragm of the microphone or the strings of a guitar or bass are excited by the amplified sound output from the speakers to other vibrations. This manifests itself by a characteristic, usually perceived as shrill whistling. In general, the effect or sound produced by a constructive feedback via vibration, even referred to as feedback.
General
The feedback is based on the 1921 after the German physicist Heinrich Georg Barkhausen named and derived from him Barkhausen 's stability criterion. Is a mathematical condition that a linear electronic circuit begins to oscillate. It is based on his formula of the self-excitation of the system sound receiver - amp - speakers. The signal from the loudspeaker to the input signal at the microphone (or a different transducer functioning device such as an electric guitar ) and thus reinforced again and again. Feedback was for a long time in addition to distortion than is absolutely avoidable interference effect when recording music in recording studios. In particular, in emerging live concerts from 1962, this feedback was also an unwanted interference effect, usually caused by the high volume level of the amplifier. In recording studios was attended by placement of the sound source or use of sound absorption devices that direct sound, this disturbance was avoided and prevented. With vocal microphones, the effect usually is undesirable. It avoids him by the directivity of the microphones and speakers as well as their orientation. Furthermore, the microphones should be positioned as close to the sound source in order to keep the gain low can. Unused microphones are switched off or turned down.
With feedback from the speaker to the microphone, the frequency of vibration that builds up essentially by the resonance characteristics of the room is dependent on where the transducers are placed, and is therefore difficult to control. The situation is different with feedback whose pathway leads through a musical instrument - a typical example is the way of the electric guitar. Here, the frequency is substantially of the resonance characteristics of the instrument depends on, which can be easily influenced by the player - at the electric guitar, for example, by grabbing and changing the distance to the speaker; thereby the feedback to a willed used musical effect has developed, which is described below. The technical bases, however, are explained in detail in the article feedback under sound engineering.
Feedback in rock music
Johnny Watson Space Guitar ( Federal # 12175 ) was taken on February 1, 1954, Hall and feedback effects from the guitar and is therefore a first pressed to record feedback. The Beatles were probably the first rock group that has feedback consciously used as an audio effect. In the intro of the Beatles Hits I Feel Fine, taken from October 18, 1964, two seconds are audible feedback. In this song they first used amplifier feedback. From the press referred to as " electronic accident", John Lennon sat consciously the amplifier feedback. Paul McCartney played on his electric bass is an A, which jumped on Lennon's Vox AC30 amplifier - the first feedback of rock music on record was born. During the recording sessions for the third single Anyhow, Anywhere, the rock group The Who on 13 and 14 April 1965 in London's IBC Studios feedback in the instrumental part was listening to the final mix from producer Shel Talmy and arrived on the single. Frowned upon by acoustic aestheticians, the single was released in May 1965 to tenth place of the British charts. On October 13, 1965, this effect was used again by The Who when recording the backing tracks to hit My Generation in the IBC Studios extensively. Pete Townshend's Rickenbacker guitar broke with their pickups in particular the outro, the feedback effects. This Outro presents electrical chaos with thrown objects against the drums and on and exhibiting the pickup. Following the publication on 29 October 1965, there was great excitement at trade and public. With a ranking of Two The Who reached the top chart position of their career. The eponymous album contained with Out in The Street another song with deliberately inserted feedback. Thus, The Who became the model for a legitimate feedback as sound design in rock music, used as an extended technique.
Jimi Hendrix sat feedback especially when playing live excessively and even perfected melody leading feedback noise. This is particularly evident in his interpretation of the Star-Spangled Banner on August 18, 1969 at the Woodstock Festival. Depending on how the guitarist positioned to his amplifier, it is possible to control the pitch of the feedback. His feedback, wah -wah and Fuzztone - charged solos were his trademark. Another extensive and controlled feedback produced by Shel Talmy brought the group Creation at her, published in November 1966 Hit Painter Man in the outro.
The second album by the band The Velvet Underground, White Light / White Heat December 1967 attention especially because of the excessive use of distortion pedals and feedback. In July 1975 published Lou Reed, former member of Velvet Underground, the double album Metal Machine Music. It consists only of guitar feedback and distortion and was seen as an attempt by his record contract and / or his former manager (of which he felt gagged both financially and artistically as well ) get away. Sonic Youths characteristic feature are from 1982, in particular the guitar feedback.