I decided to take a look at your code and I found it very clean and I'm surprised by how little code there is (that's a good thing!). I'm thinking maybe you used audio files that were smaller in size and that's why you don't have a delay.
It may be about audio size, or even format. I worked hard to optimize the size of the background sound, OGG is amazing with large looped sounds, even with the lowest quality the loss is minimal. Also, for small sounds I'd use OGG without looping over a raw WAV file.
