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How to Use Reverb While reverberation can add interesting effects to a sound, one of the most interesting things about it is that reverb occurs naturally, and does not require any special equipment to produce it. Reverb is an indirect sound, meaning it does not take the most efficient path from the source to the listener. Just as light waves are reflective, sound waves are as well; it is this reflection that causes reverb to occur.
Reverberation helps maintain the energy of a sound and the distribution of the sound to the listener. While outside equipment can accentuate or enhance already-existing reverb, there is always some degree of reverb taking place when someone speaks or plays an instrument. But the addition of reverb can be useful in improving the overall quality of a sound recording. It is primarily used to give the impression of acoustic space. One should also keep in mind some amount of vigilance when working with reverb, though, as too much of it will distort sound.
Reflections
The sound reflections that create reverb are not random and erratic. The directions a sound wave travels and reflects off of tend to specific; a sound wave does not just bounce all over a room. Reflections are also proportionate to the shape and size of the room in which they are being played, and even proportionate to the position of the listener and the source that produces them. However, this accuracy and proportion fades over time.
Types of Reflection
There are two types of reflections that take place during reverb: early reflections and diffuse reverberation (also called late reflections). Early reflections are significantly smaller and slower than later ones. Late reflections are faster and more erratic; they are also less proportionate to the characteristics of the room. There are some reverberation tools that allow having independent control over both types of reflections.
Reverberation Time
Reverberation characteristics are measured with reverberation time, or the time it takes for a sound to decrease to 1/1,000,000th of its original amplitude. A sound that remains audible for a long time before it is absorbed by the room has a long reverberation time. Reverberation time is controlled by the size and shape of a room; however, the objects in the room also have an influence. Reflective objects such as hardwood floors increase reverberation time because the sound waves have more opportunity to reflect. However, materials such as carpet and drapery are absorbent, and decrease reverberation time, because they absorb the sound waves and do not give them a good opportunity to bounce. But the room itself does not have total control over reverb. Air qualities such as humidity can affect this characteristic as well.
Tools to Create Reverb
There are several tools that can produce reverb, including a stomp box, a reverberator, or a signal processor. Spring reverbs are both inexpensive and useful in accentuating the reverb of a sound recording. These metal boxes are commonly used in electric guitars to enhance reverb both when recording and in live performance. A spring reverb gathers sound at a transducer, and then travels through a spring. At the end of the spring, a second transducer converts the motion of the spring into an electrical signal. Once the sound waves hit the transducer, they reflect back up the spring, causing the reverberation effect.
Plate reverbs, while effective, are not used as often, due both to their bulk and their high price. Like a spring reverb, plate reverbs use transducers, but instead of a spring, plate reverbs use a metal plate to reflect sound. Reverb can also be created digitally, using filters and buffers. Digital reverb manipulation involves simulating reflections using response filters; the two most common are the comb filter and the allpass filter. The allpass filter is particularly effective because it computes all frequencies evenly. But although digital filters can be extremely effective, they do not quite produce the same quality of reverb that spring or plate reverbs can. However, creating reverb digitally is significantly cheaper.
Reverb is Not Delay
Some people might think that a delay device can produce reverb, as the reflected sound waves are sounds that are delayed in getting to the listener’s ear. However, the speed of reflecting waves changes as they bounce and travel; a delay device cannot create these changes the way a signal processor can. Nor does a delay device actually cause sound waves to reflect off physical object. As opposed to being a reverb tool, a delay device is, at best, a simulator.
Reverb Chamber
In addition to using specific tools to enhance reverb in a sound recording a reverb chamber is another useful technique. Reverberation chambers are a common way to incorporate extra reverb during the recording process. If there is no fancy chamber in a studio, areas such as elevator shafts and stairwells work very well, as long as there is some absorptive material in the area to help control the effect.
Types of Reverb
There is more than one kind of reverb. Two main types are gated reverb and reverse reverb. Gated reverb creates decay in the sound; this truncation can either be gradual or abrupt. It is produced using a reverberator. To do so, shorten the signal impulses of the device; this reduced the number of reflections a sound can make. Reverse reverb, on the other hand, simulates reflections as a sound’s volume increases; gated reverb works as volume decreases. Also unlike gated reverb, reverse reverb always cuts off abruptly; there is no gradual fade. Both of these techniques are most commonly used in digital sound editing.
It is important not to confuse reverb with echo. An echo is a delayed sound, and this delay repeats itself until the sound fades out of hearing range. Reverb is not a repetition of an original sound. When we hear reverb, we are hearing the reflections of distinct sounds, not copies of old ones.
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