Hi. Sorry if it's the the wrong category.
How to measure the decibels who come out from my headphones? I use Winamp as music player. Winamp is set to 100%. When i go to audio settings, my speakers are set to 14 (%) and Winamp at 13.
Easiest and fairly accurate way is to use a sound level meter. Use a piece of cardboard or a CD to create a seal between the pads and the meter.
If you have a smart phone there might even be an app for it (probably not as accurate as a calibrated sound level meter though).
You can also calculate sound pressure but you'd have to know the output level of your sound card.