I wonder if any other viewers have noticed the background noise heard during television commercials for Flight Centre Travel Agents?
The sound is like the vibrate function on mobile phones. During Flight Centre commercials, It's heard during the section listing airfares and various special holiday packages, and at the conclusion where an actor dressed as an airline pilot gives Flight Centre's telephone number.
Whether this is some kind of subliminal advertising technique to convince me to use Flight Centre when next booking a holiday, I don't know.
Perhaps this is something that can be investigated by the ABC's The Gruen Transfer.