title: Boost / increase volume of text to speech (AVSpeechUtterance) to make it louder
body: <p>I have a navigation app that gives direction voice instruction (e.g. " In 200 feet turn left") using <code>AVSpeechUtterance</code>. I have put volume to 1 like so. <code>speechUtteranceInstance.volume = 1</code>, but still the volume is very low compared to the music or podcast coming from the iPhone, especially when the sound is on a Bluetooth or cabled connection (like connected to car with Bluetooth)</p>
  
  <p>Is there any way to boost the volume?
  (I know this has been asked before on SO but so far have not found a solution that works for me.)</p>