Stationary / standing waves
Standing or stationary waves are a fixed pattern of interference. Interference occurs when one lot of waves interacts with another lot of similar waves. They are usually produced when a wave reflects backwards and forwards in an enclosed space so that the wave interferes with its reflection. In musical instruments this commonly happens in a string or within a tube containing air.
The notes below provide general introductory of explanation with illustrated examples. There are single sheets of notes concentrating on standing waves in strings (or wires) and the second in tubes.
The final sheet runs through the standard experiment used to find the speed of sound in air using a standing wave in a tube.
Two free video lessons on standing waves can be viewed here.