we live in small town, only one fire station and not a whole lot of crime, so sirens are not a problem. But our lab really starts in howling before we hear the sirens, maybe you live near a fire station? Police Station? or some sort of factory with a high pitch machinery? It can really hurt their ears. I guess we are lucky enough that our neighbors like our dog too, they have told us many times they are not bothered by his barking, they rather feel safer. We have a yorkie also...who stays inside 99% of the time, when Beau (our lab) barks outside, Chewy runs to all the windows in the house...looking to see what Beau is barking at, as if he is the boss and checking the seriousness of it all.
I don't think we could survive in this world without our little helpers! Have a nice evening