Yes, it is possible to make the detected silences completely silent without actually removing them. In the silence detection tool, select “Select Silences” instead of “Delete Silences”. Then, from the main menu, select “Effects / Silence”. This will make the detected areas completely silent.

It is also possible to make all the silences the same duration. Use the “Select Silences”, and then, from the main menu “Effects / Insert Silence…”. You will be asked for the duration of the silence to insert, and all the selected silences will be replaced with a constant duration silence.

For the fade in and out, you can select fade in and fade out from the Effects menu, but this will apply a fade on the whole duration of the silences. I was about to write that it was not possible yet to do this with TwistedWave, but I found this solution:

- Create a new document (File / New).
- Insert a silence (Effects / Insert Silence…). Make sure the silence is at leas as long as the longest silence in the file you want to process.
- Select all and copy to the clipboard.
- Close this new document.
- From the main menu, select “Edit / Special Paste Options…”.
- Select the “Replace” mode, check the option “Fade document”, uncheck “Fade clipboard”, set the attenuation to -infinite, and specify the duration of the fades in the “Fade in/out time” box. Press OK.
- Now, select the silences with the silence detector in “Select Silences” mode.
- Select “Edit / Special Paste” from the menu to apply all the fades in and out on the detected silences.

This is not a very straightforward process, but will do the job. I should definitely add the possibility to do these three kinds of silence deletions from the silence detection window. I will think about it for a future update.