First year ice fishing, went on lake medina for a change, had 7 inches of ice and it was pretty clear. walked Around the shoreline to get to the spot we wanted and it started making this hallow doinking noises, we drilled four holes about ten feet apart from the two of us, the sounds seemed to become more frequent and being inexperienced, we got off the ice in a hurry. Is this something we should be concerned about next time we are out? it really freaked us out since we have never heard ice do that on any of the other lakes we've been on