Còi Thổi Âm Thanh Lớn "Bigg Whistle"

The original model is really loud.  You probably should have earplugs or something covering your earballs.  I just made it more obnoxious by adding an 8mm sphere inside. It doesn't work quite as well as a cork sphere found in manufactured whistles, but this will still get the job done, and it doesn't cost $20.