Works perfectly! I wanted the option to have no sound (silent) for a particular contact in Signal (which I *love* & highly recommend). The app allows you to customize notifications per contact/thread - cool! However  it does not provide the option of 'silent' under the notification sounds. It does provide that option under notification sounds for the overall default notification sound for the app  just not for a particular contact. I used Ringdroid to save a silent part of one ringtone to a new file and voila!  it worked!
January 04 2017