In the past i remember this being the best explanation to some of the basics to understand sound waves better !!
"Shive's role at Bell Labs was more than just a great lecturer: he worked on early transistor technology, inventing the phototransistor in 1950, and the machine he uses in the film is his invention, now called the Shive Wave Machine in college classrooms.
Dr. J.N. Shive of Bell Labs demonstrates and discusses the following aspects of wave behavior:
Reflection of waves from free and clamped ends
Standing waves and resonance
Energy loss by impedance mismatching
Reduction of energy loss by quarter-wave and tapered-section transformers
Original audience: college students
Produced at Bell Labs
Footage courtesy of AT&T Archives and History Center, Warren, NJ "