Exciting demonstration in acoustics by high‐school teachers’ group: ‘‘Stray Cats.’’

In Japan, to get students interested in a subject, high‐school teachers often form a group to share their ideas and inventions on education. ‘‘Stray Cats’’ is one of the most active groups in physics. The group has been proposing many exciting demonstrations, which were contrived to support students’ learning process with intuitive understanding of physics. Here, instead of using commercial equipment, they developed simple teaching tools that show physical phenomena in an exciting and attractive way, using quite common materials and daily goods. For example, the velocity of sound is measured by a pipe filled with a gas (air, CO2, helium, etc), setting a loudspeaker and two microphones in the pipe. Interference of sounds is demonstrated by two pipes with attached cone‐shaped horns at one end, which collect a source sound in different phase, and merging them into one at the other end, which produce louder or quieter sound as a result of interference. Hitting or rubbing different length of aluminum rods aids...