Helmholtz resonance and the shell
The air inside the instrument is an instrument of its own. What it does, how to play it, and how the shell shapes everything.
Acoustics and physics
Why a shaped sheet of steel makes that sound, what the three tuned partials are, and what “in tune” actually means here.
This section explains the mechanism. The first file works outward from a single struck tone field: how it makes a pitch, what the tuned partials are, and why the note behaves as it does. The second deals with the air inside the shell, which is an instrument in its own right. The third covers tuning as a measurable thing rather than a mystical one.
The handpan attracts more confident physics than most instruments, a good deal of it wrong. Where something is genuinely settled, such as the three tuned partials or the Helmholtz resonance of the cavity, these pages say so and give the numbers. Where figures vary between instruments, such as the exact Helmholtz frequency or how long a note sustains, they give a range and say it varies. Where a claim is popular but unsupported, such as the health arguments for A=432, they say that too.
The physical vocabulary used throughout is defined in Anatomy and construction. Nothing here needs maths beyond reading a ratio, though a few advanced questions go further for those who want it.
Contents#
| ID | Question | Level |
|---|---|---|
| PHY-01 | How does a single tone field produce a pitch? | beginner |
| PHY-02 | What are the three tuned partials? | beginner |
| PHY-03 | What happens when the partials drift? | intermediate |
| PHY-04 | Why does a handpan note sound harp-like or bell-like? | beginner |
| PHY-05 | Why do neighbouring notes ring when I strike only one? | intermediate |
| PHY-06 | What is sustain and what governs it? | intermediate |
| PHY-07 | Why does hitting harder change the timbre and not just the volume? | advanced |
| PHY-08 | Why does a handpan note decay so slowly compared with a drum? | advanced |
| PHY-09 | What is Helmholtz resonance in plain terms? | beginner |
| PHY-10 | How does the gu port create the deep bass whoosh? | beginner |
| PHY-11 | What is the gu tone and how do I play it? | intermediate |
| PHY-12 | How does the air cavity couple the two shells? | advanced |
| PHY-13 | Why is a handpan louder when I lift it off my lap? | intermediate |
| PHY-14 | How do shell geometry, standing waves and crossover shape the sound? | advanced |
| PHY-15 | What does “in tune” mean for a handpan, and why is it harder than for a guitar? | intermediate |
| PHY-16 | Cents, A=440 and A=432: what is actually true? | intermediate |
| PHY-17 | How do temperature and humidity shift a handpan’s pitch? | intermediate |
| PHY-18 | Equal temperament or just intonation: which does a handpan use? | advanced |
| PHY-19 | How do makers and players measure tuning? | advanced |
| PHY-20 | How do I read a tuning report or a spectrum? | advanced |
Files#
- How a note works · PHY-01 to PHY-08
- Helmholtz resonance and the shell · PHY-09 to PHY-14
- Tuning theory and measurement · PHY-15 to PHY-20
Start here#
If you read only two, read PHY-02 and PHY-09. The three tuned partials explain the notes; the Helmholtz resonance explains everything underneath them. Almost every other question in this section follows from those two ideas.
If you are troubleshooting a note that sounds wrong, go to PHY-03 first and PHY-14 second. Wobble is not always drift, and the difference matters: one can be retuned, the other cannot.
See also: Anatomy and construction, Troubleshooting, Making and tuning, Myths and misconceptions
How a note works
What actually happens in the steel when you strike a tone field, and why the result sounds the way it does.
Tuning theory and measurement
What “in tune” means for an instrument with three partials per note, and how anyone actually checks.