I think this might be one of the first recordings of a 435hz Hornet. I had to set up a ways away since my vantage point was blocked but it turned out "ok". This quiet Hornet plus two others, along with a multitude of 4004s and Vortexs, are tested first Thursdays at 3pm in a new procedure of a little over 2 min alert followed by 1 min air horn.
https://www.youtube.com/watch?v=5ftzavdVoLQ