Forgive me, as someone with zero actual knowledge in this field. This may be a naive question, but wouldn't this be fairly easily defeated by playing songs in the background?
You just need to broadcast sufficient noise to cover the signal, i.e. the S:N ratio is such that the receiver (crisp packet, microphone, etc.) can no longer see the signal above the noise floor. Now, this might mean broadcasting a loud noise signal, which could overwhelm your (or other friendly) receivers (ears, etc.) so optimal placement of the jamming noise source becomes an issue.
Generally, you want it closer to the threat than you, so that distance attenuation keeps it bearable for you but still jams possible recording devices. Or, introduce high bandwidth noise vibrations into the surfaces of the area you are in, such as windows or walls. Anyway, it's very possible and in use today in secure facilities that must be protected from audio eavesdropping.
Maybe if you simultaneously played back segments of dozens of conversations of the participants talking. That would certainly be confusing for the participants.
As an exercise in using tertiary effects to pull in signals you might otherwise be prevented from receiving, well that is pretty cool.