fadeInAudioElementVolume.ts

public fadeInAudioElementVolume (start: number, end: number, duration: number, callback?: Function): void {
  const delta: number = end - start;
  let startTime: number = null;
  let t: number;
  let factor: number;
  let frame: any;
  const tweenLoop: FrameRequestCallback = (time?: number) => {
      if (!time) {
          time = new Date().getTime();
      }
      if (startTime === null) {
        startTime = time;
      }

      t = time - startTime;
      factor = t / duration;

      this.setVolume(start + delta * factor); // or audioElement.volume = start + delta * factor;

      if (t < duration && this.getVolume() < end) {  // or audioElement.volume < end
          frame = window.requestAnimationFrame(tweenLoop);
          return;
      }   

      window.cancelAnimationFrame(frame);

      if (typeof callback === 'function') {
          callback();
      }

      tweenLoop = delta = startTime = t = time = start = frame = null;   
  };

  end = Math.round(end);  
  this.setVolume(0); // or audioElement.volume = 0;
  frame = window.requestAnimationFrame(tweenLoop);
}