I bet you can feel a Rat-L-Trap a mile away also! That's because you're aluminum boat is a great conductor and amplifier (think those are the proper terms) for these noises. Think about this...if you can hear it, what do you think the fish hear?
Interesting discussion about this last year at BassMaster U. This time of year, when most folks are fishing shallow (or sight fishing), some said to turn off your electronics. Those little "pings" may be just the thing that keep your fish from biting. Others said the fish are conditioned to the noise and it makes no difference.