No,
I think the one that theatres etc. use just broadcasts a busy signal so that all calls coming in see that the phone is in use and thus direct the call to voice mail.
White noise generators would be pretty illegal I would think -- although you can buy them here if you really have a grudge...
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No, I think the one that theatres etc. use just broadcasts a busy signal so that all calls coming in see that the phone is in use and thus direct the call to voice mail. White noise generators would be pretty illegal I would think -- although you can buy them here if you really have a grudge...