Plate Reverberation

Plate reverberation, the granddaddy of all analog audio effects, developed in the 1950s, and subsequently became the high-end artificial reverberation device of choice until the advent of digital reverberation decades later. Operation is relatively straightforward---a large metal plate, of varying dimensions, but sometimes as long as two meters, is fed with a dry input signal, and a pickup reads output signal at a given position on the plate. The typical plate reverberation characteristic is very different from that of a room, mainly due to the absence of strong early reflections, and to the modal distribution, which is nearly uniform---both result from the inherently dispersive nature of wave propagation in a plate, as discussed in the text. In spite of this, the plate reverb sound has become one of the most sought after effects in digital audio. Simulation, as in the case of the helical spring, is another interesting application of physical modeling principles not to a musical instrument, but a processing unit.



Here is a typical dry/processed (synthetic!) pair of sounds:


Dry source





But another interest of a virtual analog model might be to go beyond what is possible with a physical unit. There are many possibilities: one could employ multiple inputs or outputs, and perhaps allow these outputs to be moving on the plate surface. And of course, there is no shortage of possibilities for altering the material parameters themselves.



            single input.single output                     single input, multiple output



Here is a “dripping water” sound input to a plate, with outputs taken at varying locations…in this case, one can here various distinct frequencies picked out as the observation points pass a modal maximum:


Dripping water


Here is a rather extreme example of a plate reverb, as applied to a vocal sound---in this case, the plate is quite large, with a 60 dB decay time on the order of about a minute:


Sound Example



For much more on physical models of plate reverberation devices, see the article in the Audio Engineering Society Journal, as well as various publications by Kevin Arcas (ENSTA Paris).