DeciGauge: Noise Level Meter

DeciGauge uses your iPhone's microphone to turn "how loud is it in here, really?" into a number you can look at: a live level reading, a 1/3-octave spectrum, a daily sound-exposure estimate, and a record of every measurement you can export as PDF or CSV. LIVE LEVEL A big number and an arc gauge show the current reading, colour-coded by loudness with a plain-language line beside it (quiet as a library / normal conversation / long stays here will hurt your ears). Switch dBA, dBC and dBZ weighting instantly, pick Fast (125 ms) or Slow (1 s) time weighting, and watch Min, Max, equivalent level Leq and a rolling 60-second chart at the same time. SPECTRUM A live 1/3-octave bar chart (31.5 Hz – 16 kHz) with the most prominent band marked. It answers "is this noise low or high?" — a machine rumbling downstairs, or a high-pitched whine. Far more concrete than telling your landlord "it's loud". SOUND EXPOSURE Using the NIOSH (85 dB criterion) or OSHA (90 dB criterion) arithmetic, DeciGauge adds up the time you actually measured in the app and shows today's exposure percentage, the 8-hour time-weighted average (TWA), and a rough estimate of how long you could stay at the current level. Only time you actively measured counts — it never listens in the background all day. RECORDS & EXPORT Start to stop is one session. It saves the start time, Min/Max/Leq/L10/L50/L90 and a second-by-second curve, and you can add a note about where you were and what was happening. Pinch the curve in the detail view to look closer. When you want to file it away or send it to someone, export a one-page PDF or a CSV — both generated on your device. ADJUSTMENT A rough per-model correction table (iPhone 8 and later) is built in, plus a manual offset of ±15 dB in 0.1 dB steps. If you have a real sound level meter at hand, put them side by side and nudge the offset. ABOUT ACCURACY — PLAINLY An iPhone is not a verified sound level meter. Readings move with the model, with microphone wear and dirt, with your case and with wind, and they clip once things get loud (around 100 dB and above). So this app publishes no accuracy figure — because it cannot honestly publish one. The numbers here are a reference to give you a sense of your surroundings. They cannot be used for occupational health management, noise-dispute evidence, compliance decisions or any legal purpose. For those, commission an accredited body with a verified instrument. PRIVACY Microphone data is converted to numbers on the spot, on your device. Nothing is recorded, stored or uploaded — a record holds only the number series, and it stays on your phone. The one thing that needs the network is the banner at the bottom. No cross-app tracking, and no tracking permission prompt. Everything is usable; nothing is gated. There is one banner at the bottom of the screen, and if it gets in your way you can remove it with a one-time purchase. Removing it unlocks nothing, because nothing was locked.