Here are some comments on that strange 56Hz hum that people have been hearing in and around Auckland: Dr Moir and his colleague Dr Fakhrul Alam have dubbed the sound an unidentified acoustic phenomena. "If this is indeed the hum, then it's acoustical and not electromagnetic." Another said it was like the humming of sand dunes; yet another thought it was like someone blowing over the top of an empty bottle. And yet again: "There could be some subtle natural geological organ pipes in the hills." Whatever, the sound remains a mystery. Do you have some explanation?