Hmmm - we use IFly on our Samsung Galaxy Tab S and have the audio alerts set to sound off. In the Cardinal, I interfaced the bluetooth audio from the tab to a automobile type bluetooth unit that feeds the audio through a mini-plug to our Garmin audio panel through the music input. So far so good, we get the audio output from the iFly app via the bluetooth adaptor fed into our headsets.
All in all, we love the iFly app and its functionality and wouldn't trade it for anything else available on the market.
Mark and Joyce
'71 Cardinal