Reverb

The ratio of direct (or 'dry') sound level to reflected (or 'wet') sound level. These two levels are usually controlled from a single Effect Ratio control. (Naturally, if you have connected your reverb unit to a mixer, you can set this to 100 percent wet and then adjust the levels of direct and reflected sound from the console's fader, as described above.) Increasing the level of the artificial reflected sound compared to the unprocessed direct sound increases the perceived distance between the sound source and the listener. By applying different levels of reverb to different instruments, you make some sounds seem closer to the listener than others, and thereby create a sense of spatial depth in your mix.

The next parameter common to most units is that of Reverb Decay Time, which is how long it takes for the reverb to drop by 60dB from its maximum level. Increasing this time increases the sense of size of your virtual room — think of the difference between a small stone church and a massive cathedral. However, an increased inside surface area in a room reduces the decay time, and this is one of the reasons why the presence of an audience 'dries out' the acoustic in a venue compared to that experienced at the soundcheck. Furthermore, the less enclosed a space is, the shorter its reverb decay time — an open field is much less reverberant than a barn.

More well-specified reverberators have additional High- and Low-frequency Damping parameters, which allow you to shorten the reverb decay for the frequency extremes. While simpler reverberators may not have independent control over these damping parameters, you are often given a choice of reverb models (for example 'Room', 'Hall' and 'Plate') which provide different preset damping combinations.

When little Low-frequency Damping is used, the simulated space seems more solidly built and sizeable — large caves, for example, have a characteristic rumble to their reverb, whereas most normal rooms have very short low-end reverb times. High-frequency Damping helps to simulate the absorbance of high-end by soft funishings, carpets, curtains and so forth — furnished rooms usually sound 'warmer' than those which are unfurnished. However, in very large acoustic spaces the reverb time at high frequencies is also reduced by the damping effects of the air itself, which are concentrated at high frequencies.Another common parameter in reverb units is Pre-delay Time, which allows you to specify the amount of time between the start of the direct sound and the start of the first sonic reflection. Decreasing this time moves the sound source closer to the boundaries of your simulated room, but also moves it further from the listener — if you use reverb on an 'in-your-face' pop vocal you should not use too short a Pre-delay Time.

Even if you only adjust parameters for Direct/Effect Levels, Reverb Decay Times and Pre-delay, you have enough control to create a wide variety of useable reverb settings. A good way to find the one you need is first to decide on the type of environment within which you want your sounds to occur. Then, by considering the physical design of that imaginary space, and by applying what you know about the basic reverb parameters, you can often get pretty close to the ambience setting you're after straight away.