Perception Exhibition

The brief

• ·The exhibition's whole premise was perception itself, so the audio installation couldn't just play sound at people through headphones - it needed to feel physically present in the room, something visitors walked through rather than listened to.
• ·One exhibit specifically had to use binaural beats - an effect the brain constructs from two tones, not something you can record and play back directly.

Approach

Human hearing covers roughly 20Hz to 20,000Hz. Brainwave activity - the alpha, beta, theta and delta bands an EEG picks up - sits far below that, around 0.5-40Hz, and is inaudible on its own, full stop. Binaural beats are the workaround: play two slightly different tones, one to each ear - 136.10Hz and 144.10Hz here - and the brain perceives the 8Hz gap between them as a slow pulse rather than two separate pitches. That particular 8Hz sits in the alpha range, associated with a relaxed, wakeful state, which is why this section of the exhibition reads as calm rather than clinical.

Building the installation

• ·Rather than synthesising the two tones from nothing, they came from a single field recording - forest ambience captured on a Zoom H5 - with the target frequencies pulled out using EQ instead of layered on top. The tones were already in the material; the job was finding them, not inventing them.
• ·Placement followed a related rule: people localise a sound source far more precisely at high frequencies than low ones, which shaped where each element sat in the installation's panning and how the piece revealed itself as visitors actually moved through the room.

Result

What visitors ended up walking through was a physical, spatial version of an effect normally locked inside a pair of headphones - taking something abstract and psychoacoustic and giving it an actual place in the room.