Continuesly app run in background

I want to play an audio continuesly when app is on background mode. I did the following thing. But it is not working. Why?

  private backgroundMode: BackgroundMode,
  private nativeAudio: NativeAudio) {
  this.backgroundMode.on("activate").subscribe(() => {
	this.nativeAudio.preloadComplex('newAlarm', 'assets/media/alert.MP3', 1, 1, 0);
	setInterval(this.alarm, 10000);

alarm = () => {'newHire');

I did this like the examples in this link.