Sound Meter for Android is an app that uses your phone's microphone to measure the sound pressure level (SPL) of the surrounding environment. The app displays the results in decibels (dB).

The microphone is usually built into the phone's handset, but it may be in a separate module. The most common arrangement is to put the microphone near the ear, i.e. in a headset.

When the microphone is near the ear, the sound is captured and transferred to the phone where it is processed and displayed on a graph. The maximum value that can be displayed is determined by the hardware.

To use the app, open it, select the "Sound Meter" tab, then the "Measure" button. In the next screen, select the microphone, then tap on the "Start" button. The results are displayed in the screen.