Weishampel (1981) did an extensive study of the vocalization potentials of the crest paying particular attention to the Parasaurolophus. He equated its tube with a trombone and by application of simple acoustical theory, he calculated the resonant frequencies of a tube. Long tubes resonate with lower frequencies than shorter ones. The lowest note obtained from a given tube is called the FUNDAMENTAL FREQUENCY. Weishampel calculated the fundamental frequency for the Parasaurolophus to be 48Hz.