Go to a quiet environment. Plug your headphones into your computer and put them on your ears. Then click on the "calibration file" button on the the right side of this screen. Listen to the sound of hands rubbing together.
Now sitting in front of your computer, remove your headphones and rub the palms of your hands together in front of your nose. Listen to the loudness of this sound.
Next, put your head phones back on and press the "calibration file" button again. Adjust the volume on your computer up or down to match the loudness of you rubbing your hands together in #2. Repeat steps #2 and #3 here until both sound levels match.
Once matched, don’t change the volume level on your computer during the rest of the test. Put your headphones on! You are ready to proceed with the test.