ARC SHIELD

If a sound hurts, it is already too loud. Protect first, identify later.

• Hearing protection. Foam earplugs, rolled thin and fully inserted, then earmuffs over them for very loud sound. Carry a pair; they weigh nothing.
• Know its limit. Earmuffs over earplugs add only 5–10 dB over one alone, and NIOSH calls even double protection inadequate above 105 dBA. Close to a hailing device, distance and cover do more than anything you wear.
• Leave the beam. Acoustic hailing devices are strongly directional. Moving sideways out of the line they point along drops the level faster than walking straight back.
• Distance. In open air, every doubling of distance cuts the level by about 6 dB.
• Hard cover. A building corner, a wall or a vehicle between you and the source blocks far more than anything electronic can.
• Nothing else? Turn away and press your palms flat over your ears.
• Afterwards: ringing, pain, a blocked feeling or dizziness should be seen by a doctor or audiologist. Keep the evidence file this page made.

What this tool cannot do

• It cannot cancel or block a sound from outside. No phone speaker can cancel a loud beam in open air: cancellation only works at one fixed point, which is why it lives inside headphones.
• It cannot hear infrasound (below 20 Hz); phone microphones roll off well above that. Above about 20 kHz it hears only what its sample rate and microphone allow - run SELF-TEST to see this phone’s limit.
• It cannot name a device. It tells you what a sound is consistent with, and what else it could be.

Phones report sound relative to their own maximum (dBFS), not in decibels of sound pressure. To read real dB and get a hearing dose, give this page one reference: hold the phone next to a calibrated sound level meter (or a meter app you trust) in steady noise, and type the meter’s A-weighted reading here.

Accuracy depends on the phone and its case. A calibrated phone is a good screening meter, not a certified one; say so if you use its numbers.

Steady pink or brown noise through headphones makes ringing ears and background noise easier to tolerate. It masks sound; it does not block or cancel it, and it is capped so it cannot get loud.

Tone sessions (Schumann, solfeggio and others) live at /tones/healing.

Each recording downloads as one ZIP: lossless audio (WAV), the spectrogram, every tone and level reading, your location if you logged it, and a SHA-256 fingerprint of each file. Anyone can later confirm nothing was changed with sha256sum -c SHA256SUMS.