Assisted Resonance (AR)


Assisted Resonance prolongs reverberation by amplifying the natural resonant frequencies of a room. By supplying additional energy, the sound energy that has been diminished through absorption is partly substituted. Such a resonance supporting system consists of a multitude of channels each of which transmits an individual resonant frequency. In this process, it is important that each channel is tuned to its frequency independent of all other channels. This is achieved by using acoustic resonators with a specific resonant frequency (Helmholtz resonator). Within these resonators a microphone is installed which picks up the specific frequency. Then, the signal is fed into an amplifier and emitted from a loud speaker at another point in the room. Thereby, the phase of the amplifier must be adjusted to the resonant frequency of the room in a way that the output signal of the loudspeaker reaches the microphone in phase with the original signal. Provided that the original signal reaches the listener first and that he or she is not sitting too close to the supporting loud speaker, it is subjectively impossible – according to the “law of the first wave front” – to tell where the additional sound energy is coming from. Such a system was first realised at the Royal Festival Hall in London by P.H. Parkin (see: Parkin, P. H., and Morgan, K.: Assisted Resonance in the Royal Festival Hall London: 1965-1969, in: Journal of the Acoustical Society of America, Vol. 48 (1970), pp. 1025-35).