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Grades 3–5 · Arts & Music

Why does opening a flute hole change the note?

A flute can play many notes without changing the length of its metal body. The player blows a narrow jet of air across an opening. The jet and the air vibrating inside the flute work together, while some sound travels out through openings.

A38 visual explanationThe selected ideal effective length is 40 centimeters. With sound speed 343 meters per second, its lowest open-column resonance is about 429 hertz. The curve shows pressure variation, not particle trajectories or the size of a real flute.An opening can shorten the vibrating airLonger effective column: 60 cmLowest resonance ≈ 286 HzSelected effective column: 40 cmLowest resonance ≈ 429 HzCurve = pressure pattern, not air’s travel pathIdeal open columns; a real tone hole is not a cut end

In the diagramAn opening can shorten the vibrating airLonger effective column: 60 cmLowest resonance ≈ 286 HzSelected effective column: 40 cmLowest resonance ≈ 429 HzCurve = pressure pattern, not air’s travel pathIdeal open columns; a real tone hole is not a cut end

Two simplified open air columns show a shorter effective length and higher lowest frequency; the wave curves show pressure variation, not the path of air flowing out.

The enclosed air supports resonances: vibration patterns that respond strongly at particular frequencies. Frequency means vibrations each second. In a simple open tube, the lowest resonant frequency is higher when the vibrating air column is shorter.

Opening a tone hole near the mouth end makes the flute behave somewhat like a shorter tube. Air can move through that opening, changing the pressure pattern inside. The effective vibrating length becomes shorter and the note can rise. Closing holes can extend that effective length and allow a lower note.

The drawing compares ideal effective lengths of 60 and 40 centimeters. At the same sound speed, their lowest frequencies are about 286 and 429 vibrations each second. Real flute holes are not perfect new ends: hole size, neighboring holes and blowing conditions also matter. The comparison explains the main relationship, not a complete flute fingering chart.

About this explanation

Starting knowledge: Understand longer and shorter lengths and faster and slower vibrations.

Sources

  • UNSW Sydney, Music Acoustics — Flute acoustics: an introduction
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