not everyone is a scream queen with the ability to make that kind or any thing close we've been trained to expect as a "scream". we've probably all seen movies with armies squaring off and then yelling as they charge each other in utter stupidity, but that sounds nothing like these whistles. give a charging army these to blow in as they charge, and it would be a totally different effect. use these while hidden in the tree line like in Macbeth so you had to imagine what the thing making the noise looked like and it would be even worse. way worse than any beating drum could do

psyops are to be thought of as a minor thing at your own peril