“Assisted Resonance” in The Royal Festival Hall, London: 1965–1969

In 1964 an electronic system (“assisted resonance”) to lengthen the reverberation time over a limited frequency range was installed experimentally in the Royal Festival Hall, London. Following the success of this experimental installation, the frequency range covered was extended (to 58–700 Hz) and the installation made permanent. This paper describes the installation and operation of the permanent system, and its objective and subjective effects. Typically, the reverberation time in the empty auditorium has been increased in the 125‐Hz octave band from 1.4 to 2.5 sec.