What the .. is a profanity delay?
A profanity delay is an audio (or audio/video) device, used during live broadcasting to filter any expletives accidentally (or purposfully, of course) uttered by interviewees or phone-in participants.
Although the operation is moderately complex internally, the basic user interface has to be one of the most simple possible - a single large button. Some devices optionally allow the delay time to be preset.
During an interview, should the interviewee say a word on the station's blacklist, the presenter presses the button, and the word is wiped from the broadcast. Personal video recorders, with 'commercial skipping' operations work in a similar way.
A show with a decent budget will employ someone whose whole job is to sit on the profanity delay button.
How does it work?
The device consists of a delay-line and time stretcher. At the start of the interview, the time stretcher slowly delays the signal by more and more until there is around 7 seconds delay between the input and the output - 7 seconds being the optimal time according to various research. The speakers carry on speaking and if well executed, listeners should notice nothing.
When the fateful word is uttered, the presenter press the button, which causes the device to skip the delay line (which contains the offending word), and bring us right up to the moment.
Once the device has been triggered, it then begins time stretching again, and is primed for reuse within a short space of time.
The obvious way to beat it is to swear, wait for the presenter to press the button, then swear again immediately. However, I guess you won't be welcome on the show after that.
Many pro audio companies market profanity delays, either stand-alone or computer based. Notable models are:
Thanks to Jurph for further info.