It was established by Dr. R. Lynn Kirlin, University of Wyoming, that the Sierra sounds recorded by Al Berry of reported bigfoot showed no sign of being altered. The year long study also showed that there were no signs of re-recording or pre-recording of the tapes. The voice range of these creatures go beyond the range of an average adult human male. This would suggest that these creatures could mimic many different sounds.
It was later discovered by Dr. Kirlin that the whistles from these creatures were made through the vocal cavity. The following whistle (72a)
The following sounds were taken from the archives of Ron Morehead.
Often, usually at dusk, these creatures would approach the Sierra camp and would announce themselves with a beating or rapping sound (74a):
An extraordinary vocal exchange between a Bigfoot and Ron Morehead happened two years after the Alan Berry recordings that were used in the production of the CD. A definite rapport had been established and for the first time these creatures vocally responded to the men while they were outside the shelter. Only two men made the long trip to the camp, Ron Morehead and Bill McDowell. The Sierra camp is not in an area that you can drive to. It is an eight mile hike into a very difficult country.
The evening began at dusk with these creatures’ rhythmic rapping and then “whooping” toward the men. Ron Morehead decided to respond with his own “whoop” and thus began a vocal exchange that lasted over an hour. (74b)