In particular ...
waves in the audio frequency band,
and outer space being the Earth's magnetosphere and the magnetospheres of other planets.
Special thanks goes to Dr. Donald Gurnett of the University of Iowa in Iowa City, Iowa who provided the original audio tape and wave spectrum sides. Also, credit goes to Dr. Dennis Gallagher of Marshall Space Flight Center in Huntsville, Alabama who was the one to conceive and put together our original "Lion Roars" talk.