Mom bought me a siren for my bike. It was made of sheetmetal. It was cylindrical, ~5″ in diameter flat on one end and bowl shaped on the other with the impeller shaft sticking out. It attached to one fork with brackets, and there was a chain from the siren to the handle bar. Once riding we would pull the chain which would engage the impeller shaft against the front wheel. THE SOUND WAS GREAT. A real siren just like the large air sirens you see on the front bumper of fire trucks today. As the impeller gained speed the LOUD siren’s pitch would get higher and higher. When you let go of the chain the siren would slowly reduce in pitch and volume. So pull it again, ride faster!! WOW what a sound! OH NO my poor neighbors. I didn’t realize, I was only 10.
Sure would like to find a siren for my 10 year old son :’)