The electrical hum in the background of a call can identify precisely when it happened. Metropolitan police in London have been recording the hum of the nation's electrical grid for the last seven years, the BBC reports. And not just for fun: fluctuations in the sound enable audio forensic experts to pinpoint the time when any digital recording--of, say, a phone call--was made. The hum varies subtly, a matter of millihertz, due to power demand and supply, so that there is a consistent signature ...
To Pinpoint Audio Evidence, UK Police Record 7 Years Of Background Noise
Popular Science - 17 Dec 2012 15:58
The electrical hum in the background of a call can identify precisely when it happened. Metropolitan police in London have been recording the hum of the nation's electrical grid for the last seven years, the BBC reports. And not just for fun: fluctuations in the sound enable audio forensic experts to pinpoint the time when any digital recording--of, say, a phone call--was made. The hum varies subtly, a matter of millihertz, due to power demand and supply, so that there is a consistent signature ...
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