Listening with headphones it may be possible to detect a faint FM-like tone and white noise when no sounds are being played. This is due to the noise generated by the sound card itself. This noise is quantified by the Signal-to-Noise ratio of the card. PC soundcards typically have much worse signal to noise ratio (around 80 dB) than CD players (>90 dB).

To reduce this background noise, open the Creative Mixer and select Input/Output Options. Set all gain values to X1.

Another reason to reduce output gain values is distortions in sound synthesis. For example, certain notes in an instrument sound out of tune. This is called "aharmonic distortion."