Binaural Headphones

The short version

"Binaural headphones" are ordinary stereo headphones. What makes audio "binaural" is not the hardware but the way the sound is encoded. When you play a properly produced binaural recording through any pair of headphones, you hear sound that appears to exist outside your head — in the room around you, behind you, or above you.

How we hear in 3D

Your brain localises sound using three cues:

• ITD (Interaural Time Difference) — the tiny delay between when a sound reaches your left ear vs. your right. A sound to your right arrives at your right ear ~0.6ms earlier.
• ILD (Interaural Level Difference) — the same sound is louder on the near side. Your head acts as a shadow for high frequencies.
• HRTF (Head-Related Transfer Function) — the way your outer ear (pinna), head shape, and shoulders subtly colour incoming sound differently depending on its elevation and direction. This is how you tell "in front" from "behind" even when timing and level are identical.

Binaural audio simulates all three cues, for both ears, simultaneously.

How it's made

There are two methods:

1. Dummy head recording — microphones placed inside ear-shaped cavities on a human-shaped head (e.g. the famous Neumann KU 100). The result captures real HRTF from the environment. Extremely realistic, but you're stuck with one acoustic space.
2. HRTF convolution (synthesis) — individual audio sources are processed through a mathematical model of the ear (an HRTF dataset) using software. This is how fulldome producers work: you spatialise your Ambisonics mix in a DAW, then apply a binaural decoder plugin to render it to stereo. The result is headphone-ready 3D audio.

HRTF: the problem

Every person's ears are shaped slightly differently. Generic HRTF datasets work reasonably well but not perfectly for everyone — some people find certain HRTFs sound "front-back confused" or not fully externalised. Personalised HRTFs (measured from your actual ears) sound dramatically better, but measuring them requires specialist equipment. Some companies (like Genelec and Sonarworks) are building smartphone-based HRTF personalisation tools.

Binaural in the Fulldome Workflow

Binaural is not a delivery format for festivals — it's a monitoring and preview tool during production:

1. Build your mix in Ambisonics (3rd order HOA, 16 channels)
2. Insert a binaural decoder plugin on the Ambisonics master bus (e.g. IEM BinauralDecoder, dearVR monitor, Facebook 360 Spatial Workstation)
3. Check your mix on headphones — can you hear the intended directions clearly? Is anything "inside the head"?
4. Remove the binaural decoder before final export
5. Deliver the 16-channel HOA file to the festival

Binaural is also useful for trailers and online demos — upload a binaural stereo render of your dome piece to YouTube or SoundCloud so audiences can experience the spatial audio concept on consumer devices.

Binaural vs. Surround vs. Ambisonics

Format	Channels	Playback device	3D elevation?
Binaural	2 (stereo)	Headphones only	Yes (simulated)
5.1 Surround	6	Speaker system	No (horizontal only)
7.1.4 (Atmos)	12	Speaker system	Partial (4 height)
Ambisonics 3HOA	16	Speaker system / headphones	Yes (full sphere)

See also: Ambisonics →  ·  Back to Glossary