My dad whistled between his teeth. He was a prodigious whistler. As I recall, it was two tones alternating. Too bad we never measured how far away we could hear

My dad whistled between his teeth. He was a prodigious whistler. As I recall, it was two tones alternating. Too bad we never measured how far away we could hear him whistling, because now I’m wondering. I’d guess half a mile though.