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The Ripple Tank

Author: N.H. Crowhurst

Waves of water in a tank are reflected in the same way. You can watch this at high tide, where the incoming waves of the ocean strike a breakwater at an angle. This gives a kind of slow-motion picture of what happens to sound waves.

Acoustic architects use ripple tanks for examination of the effects of various shapes in building structure on the way waves get reflected round an auditorium. It proves a useful way of working out a good shape for a building without having to make a full-scale model and then try all over again if the acoustics are improper.

ripple tank
Use of the ripple tank

When a tone or sound is continued, reflection effects build up. A single clap, or other pulse of sound, is reflected in a sequence that can easily be traced in a ripple tank. To some extent, we can consciously discriminate between direct and reflected sounds in normal listening. But a continuous tone causes a sound pattern to be set up, called a standing wave pattern. This is similar to the standing wave set up inside an organ pipe, except that the one in the organ pipe is deliberately controlled and has a pattern in only one direction - along the pipe. Patterns in rooms or buildings are not so organized, and "stand" in several (at least two as a rule) directions across the room.

Last Update: 2011-04-01