why is there a tooting sound in discovery channel?

Question

you know, the tootittootittooot... especially in the last parts of a commercial or program

Answer 1

The only thing I can think of is that it's an audio signal to the cable company that a change in programming is coming. This is used in radio quite a bit. It should be filtered out, the engineer must be asleep at the switch.

Answer 2

that tooting sound is coming from your nose