Resonance · Dream Lab · 1109
Inner Ear
A small museum of the sounds your brain manufactures — a cabinet of auditory illusions after Diana Deutsch, plus the Zwicker phantom tone you hear in silence. The sound is the exhibit; the diagram is the placard.
Headphones required. These illusions depend on each ear hearing a different signal. On speakers, most of them collapse.
400 & 800 Hz alternate 4×/sec, swapping ears every step. Both ears always get a tone — yet you tend to hear one tone bouncing ear-to-ear and jumping an octave.
Read the design notes
The trick. One ChannelMerger(2) feeds the two stereo channels from a left-bus and a right-bus gain, via a gentle limiter to protect your ears. Dichotic tones (octave, scale) route to exactly one bus; diotic tones (tritone, Zwicker) route to both. Every note gets a raised-cosine attack and release so nothing clicks. “Left only” ramps the right channel to silence in ~150 ms — collapsing the phantom so you hear the raw physical stream. That collapse is the built-in aha.
Why the sound is manufactured in you. In the octave and scale illusions the melody you hear is present in neither channel — your brain reassembles it by grouping pitch and location. In the tritone paradox the octave is deliberately ambiguous, so “up vs down” is decided by your own perceptual template, not the signal. In the Zwicker tone your auditory system fills the spectral hole with a pitch that was never played.
Honest caveat: the “what you hear” lane is the typical right-hander model — a prediction, not a measurement. And this build is unverified on real hardware in the sandbox; it needs headphones and human ears to confirm. References: Deutsch (1974/1975/1986; Musical Illusions and Phantom Words, Oxford 2019), Shepard (1964), Zwicker (1964) and the 2025 Zwicker-tone phantom-perception study (Imaging Neuroscience, MIT Press).