When Empty Spaces is heard normally, at exactly 1:13, there is a section of the lyrics which appears to be nonsense. However If played backwards, you can hear Pink Floyd singer, Roger Waters say the following message:
-Hello, Luka [hunters]… Congratulations. You have just discovered the secret message. Please send your answer to Old Pink, care of the Funny Farm, Chalfont…
-Roger! Carolyne’s on the phone!