Cool. I remember when I was about 17 years old and I was babysitting. The people had one of those little dachshunds. I was watching a TV program and someone on the show used a dog whistle. The little dog came running in from another room with it's ears perked and stood in front of the TV screen with it's head cocked to the side. lol Before I witnessed that, I thought dog whistles were bogus. Most humans can't hear elephants either. Their pitch is really low when they communicate with each other.