Maglite 2 screams when turned on

Recently my brothers Maglite 2D fell off his car boot. The LED Module busted in it and it was replaced free of charge by the Maglite repair centre, however when I got it back, I discovered that while it works fine, it emits an ultra-high pitched squeal when turned on. It's not very loud, but it's extremely high and no-one over the age of about 30-35 can seem to hear it, but everyone under that age can hear it. I picked up on the sound even when holding it at arms length.

It happens within 3-4 seconds of turning the Maglite on, and it gets higher and higher pitch until I can no longer hear it, I've not turned it on for more than about 15 seconds because I've heard stories of maglites exploding. Is this something I should be worried about? Happens with standard D cells (haven't used nimh's or anything), currently fitted with a stock maglite led bulb, there doesn't seem to be any areas that heat up abnormally, but the noise is pretty annoying, and I'm not sure how I can fix it. Should I send it back or is this anything to be concerned about?

Send it back it obviously isn't right.

It's induction hum, a small percentage of all our flashlights have it; there's someplace along the circuit path where a microscopic bit is slightly loose, so that when a current passes through it, it vibrates with the current and produces an audible sound. This makes no difference at all in the functionality or operation of the light, if the sound doesn't bother you, you can leave it.