I was a traffic cop for three years back in the '70's. I worked outside directing traffic and drove a Harley Davidson police motorcycle in all four seasons in Minnesota. I used either a nickle-plated brass whistle with a rubber mouth guard or a standard black plastic whistle. If I recall correctly, all of my whistles had cork balls. The whistles were on a lanyard and hung on the outside of my coat. I blew them frequently except when traveling on my open three-wheel motorcycle.

I did almost have several body parts freeze up, but never the pea in my whistle.