from the can-you-hear-that dept.
illtud writes "It appears that the Metropolitan Police in London have been recording the frequency of the mains supply for the past 7 years. With this, they claim to be able to pick up the hum from any digital recording and tell when the recording was made. From the article: 'Comparing the unique pattern of the frequencies on an audio recording with a database that has been logging these changes for 24 hours a day, 365 days a year provides a digital watermark: a date and time stamp on the recording.'"
If you sell diamonds, you cannot expect to have many customers.
But a diamond is a diamond even if there are no customers.
-- Swami Prabhupada