https://i.imgur.com/JdSt6GL.png
What does this legend represent -1 to +1 of what?
What is it useful for?
I think a db peak meter scale would be more useful.
right-click in that vertical scale and select dB - this will change to Waveform dB view.
If you want that for your default you can set it in Tracks Preferences. See: https://manual.audacityteam.org/man/tracks_preferences.html
WC
This bugged me for ages when I started using Audacity.
I still think that the +/- 1 scale is a bad choice (a dB scale would be much better), but the reason behind it is interesting.
As you are probably aware, “signed 16-bit” audio data allocates 16 binary digits to each audio sample. Each “point” on the waveform is represented as a binary number from 0000000000000000 and 1111111111111111. In decimal, this works out as a range from -32,768 through 32,767.
Similarly, signed 24-bit data represents each sample with 24 binary digits, which works out as a range of -8,388,608 to 8,388,607.
Question: If the numbers for 24-bit can go 256 times higher or lower than 16-bit, why are 24-bit audio files not 256 times louder than 16-bit files?
The answer is not terribly surprising. It’s because whatever the format, the sample values are “normalized” to the same range. In effect, 16-bit sample values are divided by 32768 to give their effective value, and 24-bit sample values are divided by 8,388,608, giving an effective range of +/-1.
This works out very neatly for floating point formats (Audacity uses 32-bit float internally), which use the actual numeric values +1 and -1 as 0 dB.
So the short answer to the question “What does the legend represent -1 to +1 ?” is: “because that is the actual, normalized range of sample values”.