If you have 16 bit WAV/FLAC/AIFF files that have dither noise where it should be silent, you may want to remove the dither noise from the "silent" sections (so that they become true silence). Here's how to do it (losslessly) using Audacity 1.3.12.
- In Audacity "Edit > Preferences > Quality" set the Default Sample Format to "32-bit float" and High Quality Conversion > Dither to "None".
- In "Edit > Preferences > Interface" set the Meter/Waveform dB range to -145 dB.
- Download and install "NoiseGate version 2.4" from here: viewtopic.php?f=39&t=30996&p=100910#p100910
- Import the 16 bit file into a new Audacity project.
- With the NoiseGate effect, use the Analyse Noise Level function on a "silent" (dither noise only) section of track. Note the reported noise level (ignore the suggested setting) - it should be around -72 dB if shaped dither was used, and around -90 dB if triangle dither was used.
- (Optional - switch the track display to "Waveform (dB)". This will make it a lot easier to see the dither noise disappear).
- Select the entire track, and call up the NoiseGate effect again and use the settings listed below *
- Export the track in a lossless format.
Select Function: -> Gate
Stereo Linking: -> Don't Link Stereo
Apply Low Cut Filter: -> No
Gate Frequencies Above: -> 0.0
Level Reduction: -> -100 dB
Gate Threshold: -> Set this to 1 dB above level displayed by the Noise Analysis step.
(For example, if the noise analysis indicated that the noise level is -90.3 dB, set the Gate Threshold to -89.3 dB.)
Attack/Decay: -> 250
The picture below shows 4 tracks with Waveform dB track display at the end of a fade-out.
Track 1 - the original 32 bit audio.
Track 2 - The audio from Track 1 after being exported as 16 bit WAV (with dither).
Track 3 - After applying the Noise Gate to Track 2.
Track 4 - After re-exporting Track 3 as 16 bit WAV (without dither).