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Have you spent many a restless night debating the improbable question; ‘If a tree falls in a forest and no one is around to hear it, does it make a sound?’ If so, and if you were one of the fifty people that attended the Science of Sound at Delilah’s Lounge Friday night, March 18th, located on South Cayuga Street in Ithaca, NY, you would have been able to put your mind at ease. Spectators at the CLASSE-sponsored outreach event witnessed how a sound wave travels from a sound source through the air to the sound receiver (the ear) much like the coils of a Slinky behave when fed through a pipe and pushed from one end. Delilah’s guests discovered that it is the vibration of air molecules that actually generates the sound; a receiver sensitive to the frequency of that sound will hear it.
Introducing this sort of science content may seem completely inappropriate for a Friday night event at a bar. However, the CLASSE outreach team made sure to bring along a vast collection of interactive demonstrations, hands-on exhibits and a hefty dose of humor to Delilah’s to dispel the belief that learning science is boring and the material is unapproachable. Since sound waves are easy to hear but impossible to see, Lora Hine and Erik Herman developed a series of visual demonstrations to illustrate how sound travels in air, strings and tubes. Audience members got involved and set the tone for a fun-filled evening of science concepts introduced using Slinkys, springs, strobe-lights and strings to help model sound waves.
Audience interest really intensified when the Ruben's Tube was fired-up! This tube consists of a metal perforated pipe with one end sealed using a small speaker hooked up to a frequency generator and the other end attached to two small propane tanks. The gas flows through the pipe, leaks out from the perforations, and is lit to reveal an amazing standing wave forming within the tube! Spectators ‘oohed’ and ‘aahed’ as the frequency was changed and the flames emanating from the tube danced up, down then back and forth to illustrate areas of higher and lower pressure within it.
After the flames were doused, people couldn't wait for the interactive, exploratory session to begin. Participants were anxious to get their hands on the Chladni plates (which formed exquisite patterns when salt was scattered on the metal plate and then stroked with a fiddle bow), hoot tubes (demonstrating standing sound waves in air excited by convection currents) and vibrating speakers (depicting nodes and antinodes formed when an elastic material is vibrated at different frequencies). Folks got a kick out operating the gummy-bear torsional wave, making tunes with their teeth, fiddling with tuning forks and listening to talky-tapes.
The evening wrapped up with the audience playing an orchestra of instruments and generating a series of songs using four notes created by blowing on tubes, glasses and banging on boom-whackers. Participants yearned for more, but the evening had to come to a close. The inquiry into sound had evoked a sense of curiosity and excitement in the minds of those who partook that evening at Delilah’s; inspiring the CLASSE outreach duo to begin preparations for additional programs in the near future. So, if you still are uncertain if a tree smacking against the forest floor would create the vibrations necessary to generate a sound wave at a frequency the human ear could hear, then be sure not to miss the next Science of Sound installment!
Submitted by: Lora Hine, CLASSE, Cornell University