The Sound Field & the Room
The techniques part placed sound at an angle — left, right, above, behind. But a real source is more than a direction. It sits at a distance, it may move, it radiates differently depending on which way it faces, and it lives in a room that colours and surrounds it. Get the angle right and everything else wrong, and the result is a sound that is pointed in the correct direction but feels flat, dry, and stuck at your ear.
This part covers the acoustic and perceptual layer that turns a placed source into a believable one. The recurring lesson: a spatializer does not just position a source, it must reproduce the cues the auditory system uses to judge space — and those cues come as much from distance, air, motion, and reverberation as from direction. Throughout, we build on the perception established in Fundamentals: Psychoacoustics.
Chapters
- Distance & Air Absorption — the inverse-distance law, the direct-to-reverberant ratio, air absorption, near-field effects, and how distance is modelled parameter by parameter.
- The Doppler Effect & Moving Sources — pitch shift from motion, variable delay lines, interpolation artefacts, and when to apply it.
- Source Directivity & Orientation — why real sources are not omnidirectional, and how facing and radiation shape realism and distance.
- Reverberation & Room Models — the room impulse response, RT60 and ISO 3382, convolution vs algorithmic vs perceptual reverb, and spatial reverberation.
- Direct, Diffuse & Envelopment — apparent source width, listener envelopment, coherence, decorrelation, and the comb-filtering trap.