Flute Pipe Lengths

This simulation shows how the air inside a pipe makes a note. Students drag the ring at the top of a pipe up or down and hear the pitch glide as the length changes. Clicking a pipe, or pressing keys 1 to 6, blows it. A select control switches between an open pipe and a pipe closed at one end, and a slider chooses the first, second or third harmonic. Moving dots show air displacement, red for compressed and blue for stretched, slowed down so they can be seen. Readouts show length, frequency and the formula used. It teaches standing waves, resonance and why closed pipes sound an octave lower.

• Drag the ring on one pipe upward and listen to the pitch fall as the pipe gets longer.
• Switch to Closed pipe and blow the same pipe again; compare the frequency with the open pipe.
• Set Harmonic n to 2 and then 3 and watch the dots form more nodes in the air column.
• Make two pipes the same length and check that their frequency readouts match.
• Press keys 1 to 6 to blow each pipe and note which is highest.

1. 1Explain how pipe length changes the pitch of an air column.
2. 2Compare the frequency of open and closed pipes of equal length.
3. 3Describe nodes and antinodes in a standing sound wave.
4. 4Use f equals v over 2L and f equals v over 4L to calculate frequencies.

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