In this video, a pilot makes the embarrassing mistake of announcing the passengers on an active frequency. During the video, other pilots are apparently trying to get his attention by sending some sort of beeping noise. What are they doing to get his attention?
Anybody keying the mic on the same frequency the unfortunate PA-over-the-radio pilot is transmitting on is accomplishing nothing productive whatsoever, and anybody with access to such a microphone ought to be smart enough to realize it. When a radio is transmitting on a frequency, it isn't receiving on that frequency (since the only thing the receiver could possibly hear is your own transmission), and so anybody keying their mic on top of his isn't being heard by the unfortunate pilot who is making his PA over the radio. (Nor is their transmission likely to be intelligible to anyone else on the frequency.)
The "beeping" or squealing noise heard in the video is simply what's received (i.e. by a third radio) when two transmitters are both transmitting on the same frequency. Neither station that's transmitting hears it.
(There's those who have, and those who haven't yet, but if you make enough PA's, sooner or later one will go out over the radio.)
If there is a second frequency that the PA'ing pilot is listening to, it's possible that a message on that frequency might be heard, but that's not always particularly likely.
The best defense I've found against this situation is to NEVER listen to your flying partner's PA's -- don't have PA audio "on" when they're talking on it. Then, if you do hear, "Ladies and gentlemen, we..." then look over at their comm panel & switch them off of COMM1 or COMM2 if that is in fact what's going on.
Nevertheless, "those who have, & those who will" still applies.
There is no way to get a pilot’s attention while they are transmitting. ATC frequencies are “simplex” meaning once you start transmitting, all incoming reception is blocked. Any pilot or ATC should know it’s impossible to reach the offending pilot.
The beeps you hear are not other pilots or ATC trying to get the attention of the transmitting pilot. The beeps are feedback caused when two radios transmit at the same time. The simultaneous transmissions are probably other pilots or ground vehicles try to transmit over the offending pilot, hoping to reach ATC ground control.
One way to get a transmitting pilot’s attention is to use another radio frequency that the other pilot may be monitoring. Another option is using datalink or ACARS to send a text message to the flight deck.