Sound Level Meter is in the 4th set of the Smart Tools collection (noise).
SPL(sound pressure level) meter app uses your phone mic to measure noise volume in decibels(db), and shows a reference. We had calibrated many android devices with the actual sound level meter with dB(A).
REMEMBER!! The smart phone microphones were aligned to human voice (300-3400Hz, 40-60dB). Therefore the maximum values are LIMITED by the manufacturers. The very loud sound(100+db) cannot be recognized. Moto Droid(max.100), Galaxy S3(81dB), Galaxy Note(91dB), Galaxy S2(98dB)...
See the 4-5nd pictures. Many devices had been calibrated by the real sound level meter with dB(A).
* Pro version added Features: - Sound Meter and Vibrometer are integrated - Statistic menu and Save log data - Level notification - Line-chart duration - More models are calibrated - No ads
* Do you want more tools? Get [Sound Meter Pro] and [Smart Tools] package.
For more information, see the manual, Youtube video and the blog. Thank you.