I've heard that the reason that Drury dog whistle style locator call is called "dead silence", is because that's all you hear after blowing it!

I think you just have to hit the birds in the right mood. I always stop and listen every time I hear a real crow or raven, and on several occasions have heard birds gobble. Then again, I've walked miles hooting, cawing, howling and had no luck hearing a gobble. Sometimes you just can't beat a sweet sounding box call for locating while strolling through the woods. You just have to be on your toes if you get a response.