I’ve never heard a Sindt, but I can tell you that my Hudson is a bit louder than my O’brien Stowaway. It’s not a quiet whistle, it’s easily heard in medium sized session but it’s not as loud as a Susato. Hope that helps.
I don’t believe there is any silver in “nickel silver”. I believe it is an alloy of copper, zinc and nickel and is sometimes called German silver. It is silver only in color but is hard, takes a nice polish and resists corrosion well. If anyone knows otherwise, feel free to correct me.
I have one of Copeland’s nickel D’s and it is a very, very nice whistle.
I have owned five Copeland high D’s, only one has the ring at the bottom of the tube. It’s a brass whistle, nice touch though.