title: xamarin forms sound control not in sync with device
body: <p>I am new to ios developement, using xamarin forms to develop online audio player. I am done with my app with my own progress bar which sets the player volume but it does not sync with device volume.</p>
  
  <p>e.g when you reduce/increase sound in device, update the same on app progress bar. 
  I am sure, i have to register and listen output volume of the device but don't know which api/event i need to use. </p>