[sliverstorm]

It's two private parties acting in a public space. It may still be illegal to interfere, but the first amendment protects you from the government, not from other individuals.

You can't just use air raid sirens to disrupt a public protest

I'm not 100% up on my civil rights/protest law, but if you are a private party, I suspect you could. It is, for example, 100% legal to surround a protest with other people holding sheets to block them & their signs from view.

[Retric]

https://en.wikipedia.org/wiki/Disturbing_the_peace

This can include creating loud noise

Of note: A violation of a noise ordinance is in most jurisdictions not considered a disturbance of the peace unless the perpetrator has disregarded an affirmative request that he or she reduce the noise to a reasonable level. However, that would be implied in the air raid siren case.

Anyway, I agree it's not the 4th that's the issue. But, it's still unlawful conduct.

[sliverstorm]

Ok, maybe no air raid sirens. But you could talk over them, which is a bit more analogous to what was done here :)

[Retric]

Talking over each other would be the same as running two or ten routers on the same channel, which is not an issue. This approach actively prevents communication.

[sliverstorm]

So... more like pressing the "hang-up" button while they talk on their phone, or pulling the plug on their loudspeaker?