Add "buzzer" functionality to acoustic vario
Story: In competition flying there are often situations where gaggle has to wait in weak lift and constantly loosing altitude (sink rate is greater than lift e.g. vertical speed varying from -0.3m/s to 0.1m/s). In this situation it is crucial to have vario with "buzzer" (flymaster call it buzzer). In current new implementation of custom vario sound it's not possible to achieve such configuration.
Proposal: It would by best to have buzzer interval fully configurable with at least 3 function points but some good default setting would be also great. x axis in custom sound config should look like this: [-7;-ST][-ST;LT-buzz]0[LT;7]
It should be possible to set ST and LT (lift/sink threshold) to 0. In that case buzzer is off. It should also be possible to disable buzzer if someone what just quite ST;LT interval.
Setting "buzz" value means buzzer starts to buzz when vertical speed is in [LT-buzz;LT].
Currently there is maximum sink threshold -0.1 which is odd as it prevents to workaround buzzer using implemented 0.9.4 BETA functionality.
What is buzzer according to Flymaster https://dnl.flymaster.net/Flymaster%20NAV%20SD%20manual%20EN%20v3.pdf I'm using Flymaster example as I know how it works but other brands also have similar functionality.
If I'm not clear enough I can provide more details. Thanks