9

Plates, Digital Reverb Effects, and Convolution Reverb
The first form of reverb used in music production was actually a special room with hard
surfaces, called an echo chamber. It was used to add echoes to the signal. Mechanical
devices, including metal plates and springs, were also used to add reverberation to the
output of musical instruments and microphones.
Digital recording introduced digital reverb effects, which consist of thousands of delays
of varying lengths and intensities. The time differences between the original signal and
the arrival of the early reflections can be adjusted by a parameter commonly known as
predelay. The average number of reflections in a given period of time is determined by
the density parameter. The regularity or irregularity of the density is controlled with the
diffusion parameter.
Today’s computers make it possible to sample the reverb characteristics of real spaces,
using convolution reverbs. These room characteristic sample recordings are known as
impulse responses.
Convolution reverbs work by convolving (combining) an audio signal with the impulse
response recording of a room’s reverb characteristics.
AVerb
AVerb is a simple reverb effect that employs a single parameter (Density/Time) to control
both the early reflections and diffuse reverb tail. It is a quick-and-easy tool for creating a
range of interesting space and echo effects. The AVerb may not be the best choice for
simulating real acoustic environments, however.
• Predelay slider and field: Determines the time between the original signal and the early
reflections of the reverb signal.
• Reflectivity knob and field: Defines how reflective the imaginary walls, ceiling, and floor
are—in other words, how hard the walls are, and what they’re made of. Glass, stone,
timber, carpet, and other materials have a dramatic impact on the tone of the reverb.
• Room Size knob and field: Defines the dimensions of simulated rooms.
168 Chapter 11 Reverb Effects