A geophone lying on the floor records the tiny tremor each step sends through the structure. No camera, no microphone, nothing worn. Below are five minutes of two people walking. Press play and listen to them.
Each strip is the full recording. The shaded box is the stretch shown and played below.
A single step is over in well under half a second. The heel strikes and the floor answers with a sharp jolt, then it keeps ringing and slowly dies away.
That ringing belongs as much to the floor as to the person. Wood and concrete ring differently, and each walker presses on the floor in their own way. Separating the person from the floor is the hard part of the research.
Most footstep energy sits between 10 and 100 Hz, the bottom edge of human hearing. Laptop and room speakers barely reproduce it, so “Untouched” needs a subwoofer.
Playing the recording faster lifts every frequency by the same factor, into the range our ears like. The price is time: a walk becomes a drum roll.
Each detected step is sped up on its own but played at the moment it really happened. You hear the true walking rhythm with a floor that sounds like a drum.