Broadcast audio delay allows a board operator to cut out a swear word without using the bleat button. For years, live radio used the bleap sound effect, but they stopped in the 19 seventies. Most of the time you didn't need bleak - it was just a tone to fill dead air while the naughtiness went away.
There's a particular one-kilohertz tone that is universally understood to be covering up inappropriate words on radio and TV. But there are other options, too, like silence -- so why did this particular *bleep* sound become ubiquitous?
Bleep!