In any case I'd guess it's the iPad not the DL "doing it".
There could be some possibility of that.
I have an old apple iPhone dock. The one with the removeable plastic inserts to suit any model 30 pin iPhone.
I use it in the shed to charge my old 3GS which has been retired to iPod use.
I used to plug into the 3.5mm audio out jack in the dock so that I was efectively using the 30 pin connector to pass the audio through the dock.
I remember having various odd sound issues and the music volume would fluctuate.
Since then I just plug straight into the iPhones headphone jack and haven't had any audio issues since.
So maybe there is some kind of tarnish on the audio specific pins in the dock on my iPad and it's enough to cause "something" to trigger the noise blast...