Ok, you are totally right, this is unacceptably long delay from our end. Let's do this - we've just implemented it as a "quick fix", in other words, it can be disable by editing allmynotes.ini file, do the following to disable alarm sound:
1. Make sure you have version 2.82 (will be released soon), or, 3.10 build 783 (can be downloaded by this link). Launch it at least once.
2. Exit from AllMyNotes Organizer.
3. Open file allmynotes.ini (by default, located in My Documnets\AllMyNotes folder) using Notepad or any other text editor.
4. Find text line AlarmSndEnabled=true, change it to AlarmSndEnabled=false
5. Save changes.
6. Launch AllMyNotes. Enjoy silence :)
And sorry that there is no UI for that yet - we are going to implement sound schemes soon, so this a temporary solution.