From 2018 (YouTube Edition): Audio Indicators Are A Critical Part Of The System Avilution is creating innovative panels for GA airplanes, and while a lot of attention is paid to the visual aspect of how flight data is presented, Avilution founder Mark Spencer says that audio cues are also an important part of the system. One of the places where an audio alert can be particularly helpful is in indicating angle of attack (AOA), Spencer said. As the AOA increases, a sound similar to a kazoo begins, and increases in both volume and pitch as the airplane gets closer to a stall. The Avilution XFS system also uses an audio cue to represent proximity over the runway. The audio makes the experience of the landing flare the same for any airplane in which it is installed, Spencer said.