Another handy piece of equipment used for measuring sound levels of audio equipment is the decibell meter.
decibell meter

It measures the sound level in decibells and displays it on the screen.
decibell indicated

My colleague snaps his fingers to increase the decibells.
increased dB

There is also a test tone for the dB meter at 95.7 dBs in this next picture.
test tone

This tools make checking the speakers in aircraft easier for us because we can just put a tone on the aircraft audio system, hold the dB meter at the speakers throughout the cabin and look for low noise levels.
This is a speaker that works.

And this is a speaker that doesn't work.
not working