Sound Meter Pro is the 4th set of Smart Tools® collection. ★★ The advanced version (Smart Meter Pro) was newly released. This app (Sound Meter Pro) will continue to be updated, but we strongly recommend that new users purchase the new version. ★★ SPL(sound pressure level) meter app uses your microphone to measure noise volume in decibels(db), and shows a reference. We calibrated a lot of android devices using an actual sound meter with dB(A). REMEMBER!! Most smart phone microphones were aligned to human voice (300-3400Hz, 40-60dB). Therefore maximum value is LIMITED by manufacturers, and very loud sound(100+ dB) cannot be recognized. Moto G4 (max.94), Galaxy S6 (85dB), Nexus 5 (82dB)... You can trust the result in routine-noise levels (40-70dB). Please use it as an auxiliary tool. Vibrometer uses the phone sensors to measure vibration or an earthquake, and it shows a reference as a seism detector. The measured values are related to Modified Mercalli Intensity scale (MMI). If it is inaccurate, you can calibrate it so that maximum value is about 10-11. Please use the results only for reference because android devices have a wide variety of performance and sensitivity. * Pro version added Features: - No ads - Sound Meter and Vibrometer are integrated - Statistic menu (line chart) - CSV file exporting - Line-chart duration - More models are calibrated For more information, watch YouTube and visit the blog. Thank you. * It is a one-time payment. The app price is charged only once. ** No internet support : You can open this app without any connection. After installation, open the app 1-2 times with your device connect to WI-FI or 3G/4G.