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Reverb effects

Reverberation imparts an acoustic space’s characteristics (room, concert hall, garage, plate reverb) to audio. Two common reverb processes are convolution reverb and algorithmic reverb. Audition includes both.

Convolution reverb is generally the more realistic sounding of the two. It loads an impulse, which is an audio signal (typically in WAV file format) that embodies the characteristics of a particular, fixed acoustic space. The effect then performs convolution, a mathematical operation that operates on two functions (the impulse and the audio) to create a third function that combines the impulse and the audio, thus impressing the qualities of the acoustic space onto the audio. The trade-off for realism is a lack of flexibility.

Algorithmic reverb creates an algorithm (mathematical model) of a space with variables that allow for changing the nature of that space. It’s therefore easy to create different rooms and effects with a single algorithm, whereas with convolution reverb, you would need to load different impulses for fundamentally different sounds. All Audition reverbs other than the convolution reverb use algorithmic reverb technology.

Each type of reverb is useful. Some engineers prefer algorithmic reverbs because it’s possible to create “idealized” reverb spaces; others prefer convolution reverb due to its “real” feel.

Convolution reverb

The convolution type of reverb can produce extremely realistic reverberation effects, and as described later, can also be useful for sound design. However, it is a CPU-intensive process.

  1. Choose File > Open, navigate to the Lesson04 folder, and open the file Drums110.wav. Play the file to hear what it sounds like.
  2. Click an effect insert’s right arrow, and choose Reverb > Convolution Reverb.
  3. Load some presets to get a sense of what convolution reverb can do. When you’re done, load the Memory Space preset.
  4. Load different impulses from the Impulse drop-down menu. Note how each impulse produces a different reverb character. When you’re done, load the Hall impulse so you can check out how the various parameters affect the sound.
  5. Vary Mix to change the ratio of dry to wet sounds.
  6. Vary the Room Size control, and listen carefully to how this option changes the size of the hall. You’ll be comparing this to the range available with algorithmic reverb.
  7. Move the Damping LF slider to the left to simulate the effect of a room with lots of sound-absorbing material, which absorbs high frequencies more readily than low frequencies. Move the Damping HF slider to the left to remove lower frequencies, creating a “thinner” but also less “muddy” reverb character. Damping LF and Damping HF affect frequency response.
  8. Move the Pre-Delay slider (which sets the time before a sound first occurs and when it reflects off a surface) to the right to increase the pre-delay amount. A longer pre-delay implies a longer time for the sound to reflect, hence a bigger space.
  9. Move Width farther to the right to create a wider stereo image; move the slider to the left to narrow the image. Adjust Gain to set the overall gain of the composite wet/dry sound. This will typically be at 0 unless you need to compensate for signal level variations caused by adding the reverb effect.
  10. Leave Audition open for the next lesson.

Studio Reverb

We’re covering these reverbs out of sequence because the Studio Reverb is an algorithmic reverb that’s simple, effective, and works in real time so it’s easy to hear the results of changing parameters. Many of the Full Reverb and Reverb parameters cannot be adjusted during playback, because they are very CPU-intensive.

  1. Click the current effect insert’s right arrow, and choose Reverb > Studio Reverb to replace the Convolution Reverb effect.
  2. With the Default preset selected, vary the Decay slider. Note how the range is much wider than the Convolution Reverb’s Room Size parameter.

  3. Drag the Decay slider all the way to the left, and then vary the Early Reflections slider. Increasing early reflections creates an effect somewhat like a small acoustic space with hard surfaces.
  4. Set Decay to about 6000ms and Early Reflections to 50%. Adjust the Width control to set the stereo imaging, from narrow (0) to wide (100).
  5. Move the High Frequency Cut slider more to the left to reduce the high frequencies for a darker sound or more to the right for a brighter sound. High Frequency Cut works similarly to the Convolution Reverb’s Damping LF but covers a wider range.
  6. Move the LF Cut slider to the right to reduce low-frequency content, which can “tighten up” the low end and reduce “muddiness,” or more to the left if you want the reverb to affect lower frequencies. Low Frequency Cut resembles the Convolution Reverb’s Damping HF parameter.
  7. Experiment with damping. Damping provides the same function as the Convolution Reverb’s Damping LF parameter. The difference between damping and High Frequency Cut is that damping applies progressively more high-frequency attenuation the longer a sound decays, whereas the high frequency cut is constant.

  8. Vary the Diffusion control. At 0% the echoes are more discrete. At 100% they’re blended together into a smoother sound. In general, high-diffusion settings are common with percussive sounds; low-diffusion settings are used with sustaining sounds (e.g., voice, strings, organ, etc.).

  9. Experiment with the Output level options, which vary the amount of dry and wet audio.
  10. Leave Audition open for the next lesson.

Reverb

When you call up the Reverb effect, you’ll likely see a warning alerting you that this is a CPU-intensive effect and advising you to apply the effect before playback. You cannot adjust the reverb characteristics in real time—only when playback is stopped. But you can edit the dry and wet levels at anytime.

  1. Click the current effect insert’s right arrow, and choose Reverb > Reverb to replace the Studio Reverb effect.
  2. Load various presets and vary the dry and wet sliders. Because you’re processing a drum sound, Big Drum Room and Thickener can be very useful; they’re designed specifically to enhance drums.
  3. Vary the Perception slider, which is similar to high-frequency damping; at 0 the sound is “duller” and softer, whereas a setting of 200 simulates more irregularities in the listening environment, so the sound is brighter and “harder.” Try different Perception slider settings and listen to the results; the difference is relatively subtle.
  4. Leave Audition open for the next lesson.

Full Reverb

Full Reverb is a convolution-based reverb and is the most sophisticated of the various reverbs but also the most impractical to use because of the heavy CPU loading. You cannot adjust parameters other than the level controls for dry, reverb, and early reflections levels during playback, and even then, the level control settings take several seconds to take effect (however, if you stop playback and adjust them, the change occurs immediately on playback). Also, if you change any of the non-level reverb parameters while stopped, it can take several seconds before playback begins. As a result, when you’re using this processor, you’ll probably want to start with a preset that’s as close as possible to what you want and make a few tweaks as needed.

  1. Click the current effect insert’s right arrow, and choose Reverb > Full Reverb to replace the Reverb effect.
  2. Load some presets to get an idea of the Full Reverb’s sonic potential.
  3. With playback stopped, turn the Dry and Reverberation Output Level controls to 0 and Early Reflections to 100 so you can easily hear the results of changing the Reverberation parameters (Decay Time, Pre-Delay Time, Diffusion, and Perception), which are functionally identical to the same controls in the Reverb processor. However, the Early Reflections options are more sophisticated than any of the other reverbs.
  4. Use the Room Size and Dimension controls to create a virtual room. Bigger room sizes create longer reverbs. Dimension sets the ratio of width to depth; values below 0.25 can sound unnatural, but try this for special effect-type sounds (reduce the monitor volume first because the volume may increase unexpectedly).
  5. Move the High Pass Cutoff slider more to the left to reduce the high frequencies for a darker sound or more to the right for a brighter sound; High Pass Cutoff works the same way as the High Frequency cutoff control in the Studio Reverb. Left/right location moves the early reflections from stereo more toward the left or right by moving the slider more to the left or right, respectively; if you want the source from which the reflections are derived to move with it, select Include Direct.
  6. Click the Coloration tab to open a three-band EQ with a high shelf, low shelf, and single parametric stage. You’ve already learned how equalization works, but a Decay parameter is also available. This sets the time before the coloration EQ takes effect. Set it to 0 as you experiment with the parametric parameters so you can hear the results as quickly as possible. As just one example, reducing highs produces a “warmer” reverb sound.
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