How does a sound card translate amplitude values to sound when playing WAV/PCM/FLAC files? I'm reading the documentation for WAV files (and importing them in C++)It seems like 44100 amplitude (this can change, and is specified by the WAV header) values get sent to the sound card every second. What I don't understand is that these amplitudes can be negative. I'm confused as to what these amplitude values represent. How can they be negative and positive? What happens when you send an amplitude value to a sound card to produce a sound that you can hear?
They represent fluctuations from atmospheric pressure.  


Positive values = increases in pressure = speaker cone moving outward
Negative values = decreases in pressure = speaker cone moving inward
Zero = no change in pressure = speaker cone in its relaxed center position = 1 atm


Since we can't hear a constant pressure, the constant pressure is averaged out and ignored, and only the relative vibrations are important.