Acuity

About

Acuity is a properly A-weighted sound level meter, a chromatic instrument tuner, and a reference tone generator bundled into one app. The free tier gives you the digital SPL meter with live stats, the chromatic tuner, a 1 kHz reference tone, and a loud-tone safety warning.

A one-time $4.99 Pro unlock adds analog-gauge and dual-display meter modes, C and Z weighting, an adjustable A4 tuner reference, the full tone library (100 Hz, 4 kHz, and a 17.5 kHz dog whistle) plus A2 to A6 notes, session save and CSV export, and a calibration wizard.

Readings stay on the device; audio samples are processed in memory and never written to disk. Acuity is honest about calibration limits and does not fake precision a phone microphone cannot deliver.

Acuity is on Google Play and the App Store for iPhone and iPad (iOS and iPadOS 15 or later). The Pro unlock is a one-time purchase on whichever store you buy it from; because each store handles its own purchases, an unlock bought on Google Play does not carry over to the App Store, or the reverse.

What it does

• A-weighted SPL meter with a digital readout, plus analog-gauge and dual-display modes (Pro)
• Live MIN / MAX / AVG / Leq stats and a 60-second time-series chart
• Chromatic tuner with a cents-off needle; adjustable A4 reference (Pro)
• Tone generator: 1 kHz free, with 100 Hz / 4 kHz / dog-whistle presets and A2 to A6 notes (Pro)
• No telemetry; audio samples are processed in memory and never written to disk

What you get free, and what the $4.99 unlock adds

Accuracy and limitations

Acuity reads sound through the microphone built into your phone or tablet. Phone microphones are consumer audio components, not calibrated measurement instruments, so absolute decibel values vary by hardware model and by mic obstruction (case, finger, screen protector). Use Acuity for useful relative measurements (is room A louder than room B; is a sustained noise above the level at which hearing damage is a concern over time; is this instrument in tune relative to A=440 Hz). Do not rely on it for legal, occupational-safety, medical, or regulatory compliance purposes. A built-in calibration wizard lets you apply a manual offset against a trusted reference meter if absolute accuracy matters for your use case.

Privacy at a glance

• No personal data is collected by Acuity.
• All app data is stored on your device.
• No analytics, no telemetry, no crash reporting.
• No account is required to use the app.

Read the full Acuity privacy policy or learn about account and data deletion.

Permissions Acuity requests

Microphone

To read ambient sound levels and detect instrument pitch. Audio is never recorded to storage or transmitted; samples are analyzed in memory and discarded.

Internet · Android only

Declared by the Google Play Billing and RevenueCat libraries to verify and restore your one-time Pro purchase. On iPhone and iPad, network access needs no permission. Acuity makes no other network calls; your audio and readings never leave the device.

Network state · Android only

Declared by the same billing and RevenueCat libraries to check connectivity before a purchase or restore. No information about you is collected.

In-app billing · Android only

Declared by Google Play Billing so you can buy and restore the one-time Pro unlock through Google Play. On the App Store, the equivalent purchase runs through Apple In-App Purchase and needs no such entry.