dBA Meter app well calibrated with professional noise meter tool OKTAVA 110A-PRO. Measure sound SPL level/noise: -Current average SPL level -Peak SPL level -Average maximum SPL level -Absolute maximum SPL level Graph histogram for (change in settings): -Current average SPL level -Peak SPL level Additional features: -Save measurements -Upside down orientation to easy use. To reset maximum or average maximum - just tap on it. You can self calibrate it in settings (range from -20.0dB to +20.0dB SPL)