Q: What is 'digital silence'?
A: This is a stream of samples set artificially to 0 (silence) at CD mastering to separate each song (usually 2 seconds). WavTrim thinks that it found digital silence if there is a long-enough continuous stream of zero samples. It then removes it very precisely. If the song contains a (more or less) silent part, WavTrim won't accidentally remove it because it is not encoded as an exact stream of zero samples (due to the analog nature of music).
Q: How are the samples removed from the WAV file? Does the file size reduce?
A: It depends. To avoid the necessity of moving around 10's of Mbytes of data, the WAV file is modified in place when possible.
Samples from the beginning of the WAV are removed by modifying the internal WAV chunk address that indicates where the music starts. So that the samples are not physically(*) removed from the file, but they are just not readily accessible anymore.
Samples from the end of the WAV are removed by truncating the file - in this case, the space is physically recovered.
(*) unless the option 'compact the file' is enabled.
Q: My favorite mp3 encoder refuses to work with trimmed WAV file. What's wrong?
A: Your encoder is only partially WAV format compliant. Use the 'compact the file' option in WavTrim, that slows down its operation but allows any encoder to work.
Q: I have trouble making a "live" audio-CD.
A: A live audio-CD should not contain silence in between tracks, the sound is meant to be continuous from track to track. One way to handle a live CD is to keep the whole CD in a single file (and use an optional cue-sheet to mark the track positions).
If you have individual tracks, WavTrim can help by trimming on CD sector boundaries (see Options/Audio-CD). This is particularly important for live CDs, as otherwise the burning software or CD writer may add silence or garbage at the end of the sectors, which creates audible glitches.
But note that if you have individual tracks of a live CD, even the sector boundary trimming option doesn't guaranty a completely glitch free result. That is why it is recommended to keep the whole CD in a single file.