Reverb Module

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Fig 1.0 Reverb Module Diagram

The Reverb Module allows you to place signals into different environments. Signals will either sound as though they are in a small enclosed space, or a large cavernous cathedral, and anything in between.

AudioGL's reverb unit also has a feedback loop system, which allows you to create unrealistic and otherworldly soundscapes, in which signals will become louder or more complex over time.

Contents

Working with the Reverb Module

How Reverb Works

AudioGL's Reverb algorithm is designed to simulate the way that sound behaves in a room. There are several components that describe this process:

Pre Delay
When a sound enters a room, there is a brief amount of time before the sound reflects off of any of the surfaces in the room. This amount of time is referred to as Pre Delay. Increase the pre-delay to a higher value if you want there to be some time between a signal, and the reverb module's response to that signal.

Early Reflections
After a sound has entered a room and passed through the pre-delay phase, it will reflect off of any surfaces that are near the signal's origin, and then any surfaces that are far away. These initial reflections are referred to as early reflections. Early reflections will give the lister a feeling for the size of the room, and the position of the signal inside of the room.

In the reverb module, the early reflections can be turned on and off, and they can also be mixed with the late reflections. Be sure to adjust these settings to get the right feeling for your sound, and to position it properly in the environment you want to create.

Late Reflections
The early reflections are sent into the late reflection part of the algorithm. The late reflections will continue to play the signal, as though it were being continuously reflected off of the walls of a room. Eventually, the sound will be attenuated and dampened to the point where it is no longer audible.

Much like the early reflections, the late reflections can be turned on and off. Turning them off will save some CPU, and can result in a much faster reverb, where only the early reflections can be heard.

Dampening
When sounds reverberate in a room, some frequencies will be dampened quicker than other frequencies, resulting in a muffled sound.

To perform dampening with AudioGL's reverb module, a feedback loop will have to be used. To get the most realistic effect, use an Equalizer Module with both the high and low shelf filters turned on, and the 'Max Boost' setting set to 2 decibels.

Modulation
The modulation system in the reverb module is tied to the late reflections. When modulation is applied, the size of the late reflection 'room' will vary, causing a slight pitch shifting effect. This effect can give sounds a bit of extra depth, and an otherworldly feeling.

When to Use Reverb

Reverb should be used when you need to create an environment for a sound that you're working on. For example, a vocal sample could be placed into a small room do make it close by, or it could be placed into a large room to make it sound distant and diffuse.

Reverb can also be used for psychoacoustic effects, which can enhance sounds or improve their stereo image. The early reflection system is particularly useful for this. If you disengage the late reflections, and simply work with the remaining early reflections, you are left with a short delay system that can add a lot of character to a sound.

Finally, the reverb can also be used to generate sounds in feedback loops. To do this, you will have to introduce a 'seed' noise into the reverb, and then shape the resultant feedback inside of the reverb. Various frequencies and harmonics can be introduced or removed from the loop, resulting in a large soundscapes.

Connecting the Reverb Module

The Reverb Module provides two typical AudioGL audio connections, which follow typical audio connection rules.

The Reverb Module can be used to create Feedback Loops, as described in the Connections article.

Parameters

Parameter Range Description
Pre-Delay time
0 to 0.2

Controls how much the signal will be delayed prior to being sent to the reverb algorithm.

Pre-Delay Symmetry
-1 to 1

When this parameter is set to '0', the signal will be pre-delayed evenly between the left and right channels. To delay the signal a different amount to each channel, adjust this parameter away from '0'.

Early Reflections Size
0 to 72

Sets the size of the early reflections. The size determines how long it takes for the early reflections to be heard.

Early Reflections Symmetry
-4 to 4

Controls the symmetry of the early reflections between the left and right channels. To get some extra stereo separation, adjust this parameter away from '0'.

Early Reflections Diffusion
0 to 1

This parameter diffuses signals as they pass through the early reflections. If set to '0', the early reflections will sound like a fast delay, where the signal is repeated but left fundamentally unchanged. Increasing this parameter will cause the sound to diffuse each time it is delayed, resulting in a softer sound.

Using no diffusion will create a sound similar to the inside of a concrete room. Using lots of diffusion will sound like a room that is filled with fabrics, furniture, or other sound absorbing objects.

Late Reflections Size
0 to 72

Sets the size of the late reflections. The size determines how long it takes for the late reflections to be heard.

Late Reflections Symmetry
-3 to 3

Controls the symmetry of the late reflections between the left and right channels. To get some extra stereo separation, adjust this parameter away from '0'.

Late Reflections Diffusion
0 to 1

This parameter diffuses signals as they pass through the late reflections. If set to '0', the late reflections will sound like a delay, where the signal is repeated but left fundamentally unchanged. Increasing this parameter will cause the sound to diffuse each time it is delayed, resulting in a softer sound.

Decay
0 to 120

Controls how quickly the late reflections will fade out over time. Increasing the decay value will cause the late reflections to last for a longer time.

Early / Late Reflections Mix
0 to 1

When both the early and late reflections are active, this parameter will control how they are mixed together. At a value of '0', only the early reflections will be heard. At a value of '1', only the late reflections will be heard. At any value in between, they will be mixed together.

If either the late or early reflections are shut off, this parameter will have no effect.

Modulation Frequency
0 to 1

Controls the frequency of the modulation applied to the late room size.

Modulation Depth
0 to 1

Controls the amount of modulation applied to the late room size. To have no modulation, set this parameter to '0'.

Reset (Edge)
0 or 1

This parameter will reset the reverb whenever it's value switches from '0' to '1'. Upon resetting, all of the sounds inside of the reverb algorithm will be cleared, after a quick fade-out.

Module Specific Options

Fig 3.0 Reverb Module Options

EROn

Turns the early reflections on or off. Turning them off will conserve some CPU. For very long diffuse sounds, or for a simple delay, early reflections are not required.

LROn

Turns the late reflections on or off. Turning them off will conserve some CPU. For short punchy sounds, or psychoacoustic effects, late reflections usually aren't required.

ModOn

Switches the late reflections modulation system on or off.

Reset Stop

Oftentimes it can be useful to have the reverb module reset itself automatically. When this button is engaged, the reverb will reset itself when the sequencer stops. If the sequencer is already stopped, you can simply reset the reverb by hitting start/stop (default keybinding: spacebar) twice.

Reset Loop

Much like 'Reset Stop', this button will cause the reverb to reset itself each time the sequencer loops.

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