Acuity: Sound Meter & Tuner

Three instruments share one microphone in Acuity: a sound level meter, a chromatic tuner, and a reference tone generator. Each one is built out properly rather than bolted on, and the same calibration model runs underneath all three. It works the same way on iPhone and iPad. MEASURE The meter shows a live A-weighted reading in dB(A) with MIN, MAX, AVG, and Leq always visible, plus a chart of the last 60 seconds. Hold freezes the number; Reset clears the statistics. A built-in sound reference guide places six anchors from 30 to 130 dB(A) against everyday examples and hearing-safety guidance. Pro adds C-weighting, Z (linear) weighting, an analog gauge, and a combined analog-plus-digital display. The weighting curves follow the IEC 61672-1 definitions rather than a label on a button. TUNE The tuner reads note, octave, cents sharp or flat, and frequency in Hz. Pitch detection is designed for low fundamentals, so bass and low guitar strings hold a stable reading. Pro adds Guitar (6 strings), Bass (4), Ukulele (4, re-entrant), and Violin (4) presets that highlight the nearest open string, and an adjustable A4 reference from 415 to 466 Hz. The standard 440 Hz reference is free. GENERATE A 1 kHz calibration tone is free. Pro unlocks 100 Hz and 4 kHz check tones, a 17.5 kHz hearing-range tone, and every chromatic note from A2 to A6, 49 in all across four octaves, each looping cleanly. The volume slider is the device media volume itself, so the hardware buttons and the app never disagree, and a hearing-safety warning appears when the tone gets loud. CALIBRATE (PRO) Phone microphones drift and differ, so Acuity gives you three ways to correct for it and keeps a history of every profile: - Reference SPL source: hold the device to a calibrator of known level and apply the measured offset - Reference meter: match a live preview to a trusted meter by sliding the offset - Tone-gen self-check: capture a baseline from the app's own 1 kHz tone to catch drift between sessions Reactivate an older profile, delete a bad one, or reset to zero. Until you calibrate, the readout is labeled uncalibrated. RECORD AND EXPORT (PRO) Record a timestamped session, pause it with Hold, and save it with a name and notes. Every session keeps its MIN/MAX/AVG/Leq summary and a per-sample chart. Export one session as sample-level CSV, or the full history as a one-row-per-session summary CSV, straight into the share sheet. PRIVACY One permission: the microphone. Audio is analyzed in memory for level and pitch and is never written to a file. Sessions, calibration profiles, and settings stay on the device. The only network activity is processing and restoring your Pro purchase through the App Store and RevenueCat. No ads, no analytics, no account. FREE AND PRO Free includes the A-weighted digital meter with live statistics and chart, the chromatic tuner at 440 Hz, the 1 kHz tone, the sound reference guide, and viewing of any saved sessions and calibration history. Acuity Pro is a one-time purchase with no subscription. It unlocks C and Z weighting, analog and dual displays, session recording and CSV export, the calibration wizard, instrument presets, adjustable A4, and the full tone library. The purchase is tied to the App Store account you buy it with. ABOUT ACCURACY Acuity is a consumer instrument, not a Class 1 or Class 2 sound level meter. Absolute readings depend on the device microphone, its case, and your calibration. It is intended for everyday and comparative measurement, not occupational, legal, medical, or regulatory compliance. Available in 83 languages. Support: https://kurokistudio.com/support/