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Quick Guide To Reverb
Reverb and echo are two of the essential core studio effects. We see what makes them repeat repeat repeat and go on and on and on...
Reverb and echo were the first ever audio effects, discovered when first man talked/grunted in a cave and shouted across a canyon. The acoustic enhancement of singing and playing instruments in large rooms was well known to the architects who designed theatres, auditoriums and cathedrals.
 The only way for early recording engineers to create reverb was, indeed, to record in a large room known as a 'live room' but this was costly and inflexible. The earliest artificial reverb devices were large springs and plates.
Affordable digital reverb units and delay lines began to appear in the 1980s followed by software reverb effects in the last few years.
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Tech terms
Wet and dry
A dry signal is the original, unprocessed signal. A wet signal is one that has been processed.
Anechoic
Literally 'without echo'. An anechoic chamber is a room designed to absorb all sound reflections and used to test audio equipment.
RT60
A techy reference to 'reverb time' which is technically the time it takes for a sound to decrease in amplitude by 60dB.
Ping pong delay
A combination of delay and panning where alternate echoes are panned to opposite sides of the stereo image. | Reverb is a very complex effect which is created by sound bouncing around the environment. If you are in a large room for example, and clap your hands, not only does the sound reflect from the four walls, floor and ceiling, but those reflections will also bounce around the room like a lot of manic rubber balls. The result is a vast number of echoes that we perceive as a continuation of the original sound.
Reverb occurs in virtually all natural environments although small rooms, rooms with furnishings and absorbent surfaces, and large fields may seem to be lacking reverb because the sound is quickly absorbed or there are no surfaces for the sound to bounce off. Our ears use the reflections to form an acoustic image of the environment, so by changing the characteristics of the reverb we apply to a sound we can make listeners think a singer is singing in the bathroom, a concert hall or the Grand Canyon.
Reverb control
Reverb units have become increasingly sophisticated and some offer control over all the parameters that make up the reverb effect. Here's a quick rundown of the major players.
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Pre-Delay This is the time it takes for the reverb to 'kick in' and it contributes to our perception of the size of the environment. Longer pre-delay times indicate a larger environment. |
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Early reflections These are the first echoes or reflections you hear. They're the strongest and the ones which come back at you from the closest surfaces - after these, what you hear are the reflections of the reflections. Early reflections also contribute to our perception of the size of the environment. |
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Density/width This is the time between the early reflections and the rest of the reverb. The shorter the time the more dense the reverb appears to be. |
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Diffusion This is how spread out or diffuse the reflections are. With low values the reflections are further apart and you may be able to hear them as discrete echoes. With higher values the reflections are closer together and sound more like reverb. |
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Reverb/decay time How long it takes the reverb to die away. The longer the reverb time, the larger the environment will appear. |
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Damping/frequency attenuation As reflections bounce around the environment, the surfaces absorb various frequencies. These vary according to the surface and how reflective it is. The highest frequencies are inevitably the first to go but the more reflective a surface is, the longer it takes the higher frequencies to die away so this gives us another clue about the environment. The longer it takes the higher frequencies to die away, the more 'life' the environment seems to have. |
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Mix This sets the balance between the wet and dry signals. |
Adjusting all these parameters to produce a realistic reverb can be quite challenging and, of course, you can produce some decidedly unrealistic effects by playing fast and loose with the parameters. If you want realistic effects it's a good idea to start with the presets and tweak the settings rather than trying to create an effect from scratch.
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