An electronic reverberation recorder

Abstract

the instrument described delineates on a cathode ray screen the decay of sound energy density as a function of time after the sound source is turned off in a room. The output from the pick-up microphone after suitable amplification and rectification is fed to a logarithmic stage to enable an energy range of 55 db. to be applied to the vertical plates of the cathode ray tube. A linear time base generator provides deflecting voltage for the horizontal pair, thus giving the decay trace in db./sec. Four values of the time for a single horizontal traverse of the spot-1, 3, 5 and 7 seconds—are provided to handle reverberation times of rooms from small studios to large auditoria. The recording speed is approximately 550 db./sec. The decay curve can be visualised by using a persistance vision screen.