7.9.5. AUDIO-05 — Reverb and Effects

This tutorial covers applying reverb and chorus effects to sounds. A short impulse burst is played dry, then with several reverb presets, then with chorus configurations, and finally with both combined.

7.9.5.1. Reverb Basics

Reverb simulates the acoustic reflections of a physical space. The dasAudio module implements the I3DL2 standard, which defines a set of named presets modelling environments from a small bathroom to a vast cave.

To hear the effect clearly, the tutorial generates a very short (0.1-second) decaying sine burst at 880 Hz. The rapid decay leaves silence for the reverb tail to ring out:

def make_impulse() : array<float> {
    let num_samples = MA_SAMPLE_RATE / 10  // 0.1 seconds
    return <- [for (x in range(num_samples));
        sin(2.0 * PI * 880.0 * float(x) / float(MA_SAMPLE_RATE)) * exp(-float(x) / float(num_samples) * 6.0)
    ]
}

Without reverb the impulse is a short “tick” that ends abruptly.

7.9.5.2. Applying Presets

set_reverb_preset attaches an I3DL2 reverb to a playing sound, identified by the sound ID returned from play_sound_from_pcm. The second argument is a value from the ReverbPreset enumeration:

var samples <- make_impulse()
let sid = play_sound_from_pcm(MA_SAMPLE_RATE, 1, samples)
set_reverb_preset(sid, ReverbPreset.ConcertHall)

Each preset models a different acoustic space with its own decay time, high-frequency damping, and early-reflection pattern.

7.9.5.3. Preset Reference

The ReverbPreset enumeration contains 23 presets:

Preset	Character
`Generic`	Neutral, medium-sized room
`PaddedCell`	Very small, heavily damped
`Room`	Average room
`Bathroom`	Small, bright reflections, short tail
`LivingRoom`	Soft furnishings, moderate decay
`StoneRoom`	Hard surfaces, clear reflections
`Auditorium`	Large hall, smooth decay
`ConcertHall`	Spacious, warm, long smooth decay
`Cave`	Massive, dark reverb, very long tail
`Arena`	Large open space
`Hangar`	Huge metallic space
`CarpetedHallway`	Damped corridor
`Hallway`	Narrow reflective corridor
`StoneCorridor`	Hard-walled corridor
`Alley`	Outdoor narrow passage
`Forest`	Diffuse outdoor scattering
`City`	Urban reflections
`Mountains`	Distant echoes
`Quarry`	Large outdoor pit
`Plain`	Open flat ground
`ParkingLot`	Concrete enclosure
`SewerPipe`	Cylindrical metallic tube
`Underwater`	Heavy low-pass filter, muffled

7.9.5.4. Chorus

Chorus adds a modulated delay to simulate multiple detuned copies of the sound, producing width and shimmer. set_chorus_default applies sensible defaults; set_chorus accepts a ma_chorus_config for fine control:

// Default chorus
let sid = play_sound_from_pcm(MA_SAMPLE_RATE, 1, samples)
set_chorus_default(sid)

// Custom chorus — slower, deeper
var cfg = chorus_config_default()
cfg.rate = 0.5       // LFO rate in Hz
cfg.depth = 0.8      // modulation depth
cfg.delay_ms = 15.0  // base delay
cfg.wet = 0.7        // wet/dry mix
set_chorus(sid, cfg)

The ma_chorus_config fields are:

Field	Description
`rate`	LFO modulation rate in Hz
`depth`	LFO modulation depth (0.0–1.0)
`delay_ms`	Base delay in milliseconds
`feedback`	Feedback amount (0.0–1.0)
`wet`	Wet/dry mix (0.0 = dry, 1.0 = fully wet)

7.9.5.5. Combining Effects

Reverb and chorus can be applied to the same sound — chorus runs after reverb in the signal chain:

var samples <- make_impulse()
let sid = play_sound_from_pcm(MA_SAMPLE_RATE, 1, samples)
set_reverb_preset(sid, ReverbPreset.ConcertHall)
set_chorus_default(sid)

7.9.5.6. Running the Tutorial

Run from the project root:

daslang.exe tutorials/dasAudio/05_reverb.das

The tutorial plays the impulse dry, with reverb presets, with chorus variations, and finally with reverb and chorus combined.