🌲 FOREST Noise Box

Calibration audio source · Perzynski install · Liliana Bloch Gallery

📢 Before use: turn phone volume to maximum, disable Silent mode (ring/action button), and keep this page in the foreground. Prop the phone at a fixed, marked distance from the EV mic so tests repeat. After START, let it play ~10 s before trusting readings — at max volume the phone's speaker-protection DSP settles in audible steps on the first sustained run.

Source

Level

dB

CAL = field reference · QUIET = CAL − 6 dB, the must-not-trigger check · MAX = bench (wired) reference · steps are exact: −6 dB = half voltage. Type a value for anything else — the minus sign is optional: 14.5 means −14.5 dB (handy on keypads without a − key).

Mode

Ready.
Continuous — steady source while you set the mixer or turn the SENS trimmer. Burst + stopwatch — plays the source for the chosen time, then goes hard-silent and counts up, so you can time how long the room must stay quiet before playback returns (the DELAY trimmer, 5–50 s).

The RDL ST-ACR2 trigger circuit is band-pass filtered for a speech-like spectrum: speech-band noise is the most realistic stand-in for gallery chatter; the pure tones are for tracing signal through the mixer (visible on the Mackie meters via channel 1 SOLO). Pair with the free NIOSH Sound Level Meter app on a second phone to log the SPL each setting corresponds to.

Gallery chatter — a five-minute crowd-murmur loop for filmed demonstrations: its loudest passages match the other sources' level, so at a given Level its swells trigger jail the way real conversation does, and its lulls hand the stage to the DELAY. Loads on first use (~3.5 MB — open it once on Wi-Fi beforehand). Demonstrate with chatter; calibrate with speech-band noise.

How the sources compare. At a given Level, the tones, warble, and speech-band noise deliver equal RMS signal voltage (full pink sits ~1.5 dB lower). That equality holds exactly for wired (bench) use. Played through a phone speaker, low-frequency sources — the 300 Hz tone and full pink — will read far lower on an SPL meter, because small speakers can't reproduce them; that's physics, not miscalibration. For acoustic work, treat speech-band noise as the reference source (1 kHz sine tracks it within a few dB), and let the SPL meter be ground truth. The Level control is exact in dB either way: −6 dB is always half the voltage.

📋 Restoration Plan  ·  Bench Certification  ·  SENS Re-Set  ·  v5.3 · 2026-09-01