One is designed to capture all sounds while the other is tuned to pick up only internal noises. (newscientist.com)
My question was I guess more whether it could really be ruled out, or whether it was obviously a ridiculous speculation on some other grounds... How you go about testing for a series of steps seems to be a bit of an issue in this case, given the amount of internal noise in the climate system.. (julesandjames.blogspot.ru)
Internal noise of combined talking, desks and chairs sliding and papers shuffling is detrimental to learning as it leads to a constant state of aggravation, restlessness, and increased movement. (educationbusinessuk.net)