Can someone tell me in what scale of numbers ia that a sound wave is converted to in voltages in positive and negative phase?
In this; link example a 180 degree negative sound wave is presented as zero volts and a 90 degree positive (full scale) wave as 5 volts.

What are the actual numbers for a given amplitude?

All that plot is showing is an analog to digital converter with a 0 to 5v range. So silence is 2.5v, and the highest possible amplitude is 5v and the lowest possible is 0v.

The scale is arbitrary though. I've got an ADC thats -1 to 1v, and another thats -5 to 5v.

The closest thing to a standard that exists for modern consumer audio is that 0dB FS (i.e. a sine wave peaking at digital full scale) gives 2Vrms output. DVD players, and many modern CD players, are quite consistent in meeting this.

However, historically there was no such standard, and it's not set in stone, so you can find a wide range of levels, even on "good quality" audio equipment. Including sound cards.

Cheers,
David.

I thought the typical output was 2 V P-P rather than RMS at 0dB FS.

G²

You go and measure it

Cheers,
David.