I have one of these vacuum breakers on my outdoor hose faucet.
Every time I turn it on, it creates a loud noise in the form of a hum or drone I can hear throughout the house. While I have been able to find many similar questions on the web, as good as my google-fu may be, I can't find any definitive answers to fix it...
I don't think it's "water-hammer" because the pipes aren't vibrating or shaking. So I believe it is just the valve itself. This just hooks up to a standard hose with a normal sprayer/wand on it.