Each dB drop exactly halves the sound pressure, IIRC, so a 3dB drop is actually dropping your sound output to 1/8 the original (1/2 x 1/2 x 1/2) output. Sound *perception* is another thing. Most people can't perceive a sound as having dropped in volume by 1/2 until it has dropped several decibels, so that 3dB drop may not sound too much different than the original level to most folks.