Decibel Meter is an application for measuring sound volume in decibels(dB).

This application in realtime shows current value of sound volume.

The main indicator shows current sound volume value and giving short explanation of it.
Also there is volume value timeline in the bottom part of screen.

This application has settings screen, which give ability calibrate decibels according to device microphone specifics.

Apple Watch application can measure sound volume without iPhone device.