From<a href="http://www.smh.com.au/news/technology/mystery-kiwi-humming-sound-captured/2006/11/17/1163266756133.html?page=fullpage#contentSwap1"> Sydney Morning Herald</a>

A New Zealand scientist believes he's captured a recording of the mystery hum that has been heard by scores of people living and in and around the city of Auckland.

Dr Tom Moir, a computer engineer at Massey University's Institute of Information and Mathematical Sciences, made the recording at a house in Auckland's North Shore suburb of Glenfield earlier this week.

Dr Moir and his colleague Dr Fakhrul Alam have dubbed the sound an unidentified acoustic phenomena.

Four people who previously reported hearing the low-level hum have confirmed that this is the sound they can hear in their homes.

Dr Moir previously pinpointed the low-level drone at a frequency of 56Hz, which is very close to the 50Hz frequency produced by the 240 volt AC main electricity supply delivered to homes in New Zealand (and Australia).

Although 56Hz is within the standard range of human hearing - which can range from 20 to 20,000Hz - it is too low for many people to pick up...

According to a theory put forward by Professor Rod Cross, at Sydney University's department of Physics, the sound could be the humming of sand dunes, as described in the latest issue of <a href="http://physicsweb.org/articles/world/19/11/4/1">Physics World</a>, a monthly academic journal.

Full story and a hum clip <a href="http://www.smh.com.au/news/technology/mystery-kiwi-humming-sound-captured/2006/11/17/1163266756133.html?page=fullpage#contentSwap1">here</a>