How many of you guys have trained your dog with a whistle? If so, what whistle works for you?

I bought a Fox 40 whistle and have trained my GSP pretty well with recall, but the thing is so loud I feel like my ears are going to burn off. Im looking for something quieter, but effective.

I have heard many UK dog/hunting trainers use the Acme gun dog whistle 210.5 or 211.5. Anyone have experience with them here?