Does opening a wav file with audacity degrade it?

Hi, I’m wanting to adjust the volumes of songs I have in wave format. So if I open a wav file with audacity then export it after adjusting the volume does the file get degraded in any way?

I have songs I created as wavs that I did not save the Audacity projects. My other, original idea was to use Windows Media Player’s “auto volume leveling” to make the (burned) CD’s songs’ volumes level but I read this may be degrading? Does any one know if this is true or not?

My goal is to make a CD of my various songs with the volumes similar. I like the idea of WMP just doing it automatically.

Also: Is there a plugin for Audacity that can evaluate a songs volume? To accomplish this as well?

Recommendations appreciated.

Strictly speaking “yes”. If you do a volume change with Audacity and write out a .wav file information has been lost. It would not be possible to read the modified file back into any program and to perfectly undo the volume change.

As a practical manner with goals in mind I wouldn’t worry. Doing manual volume adjustments song by song is unlikely to be an issue. I don’t know how WMC’s “auto volume leveling” works but it likely is some flavor of compressor which I would not recommend, unless the goal is to make mp3s to be played in your convertible while creeping down the 405. (In the latter case a compressor is the way to go).

Audacity also adds dither to the output file. Audacity does everything internally at 32-bit floating in order to avoid damage that may be caused by multiple effects and filters. The conversion back to 16-bit (assuming you’re in 16-bit) always has a slight amount of intentional noise. You can turn off dither in Preferences > Quality.

Dither is usually beneficial, though, because multiple bit depth conversions could cause audible errors if the conversion misses happen to line up.


By the way this isn’t necessarily true. “Out of the box” Audacity will default to using 16-bit integers as it’s working space. (I think the actual effects operations will still be done floating point, but after each effect the result is converted back to the default 16-bit integers). If you want to work in 32-bit float by default you have to choose that under preferences->quality.

“Out of the box” the default setting in “Edit > Preferences > Quality” is 32-bit float, 44100 Hz, shaped dither as shown here:

The issue is a little confusing as some of the importers for (some) compressed audio formats always import as 16-bit (which is a bug in my opinion).

So based on that----------- if I set my preferences to same as the wave [in this case 16bit 44khz] does this mean the wave will be exported the exact same with no degrading? After adjusting the gain/volume [under clipping of course]?

Short answer, no.

Longer answer:

  • If you change the gain/volume, then the sample values will be different to the original sample values.
  • “Amplification” is “multiplication”. If you amplify to half volume, then the exported file should have samples with half the amplitude (half the value) of the input samples.
  • “16-bit” is an “integer format”, meaning that all sample values are whole numbers (between -32,768 through 32,767).

Thus the sample values are changed such that;
output sample value = input sample value x gain factor

So what happens if the gain factor is say 0.5 and the input sample value is an odd number? Because we are dealing with integers, the “output sample value” must be rounded.
More generally, what happens if “input sample value x gain factor” is not a whole number is that the output value must be rounded.

The “losses” occur because the output sample values must be whole numbers in the range -32,768 through 32,767, and in most case that will involve some sort of rounding error.

The good news is that the error is very small and virtually inaudible.

Generally, using the Audacity default settings (32-bit float) produces the smallest amount of rounding errors and so the best quality.