The alarm zone

Human hearing is sharpest between 2,000 and 5,000 Hz — the range of alarms, sirens, and crying infants. The brain cannot habituate to it. It is not supposed to.

Most focus sound ignores this and pays for it. Every melodic tone in Particle stays below 1,200 Hz — beneath the zone evolution reserved for emergencies.

Focus sound works when the brain never registers it as an event.