• Pixel-art sticker of Hummix, personifying Helmholtz Resonance, with the caption “Blow Across Me, I Hum.”

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Hummix

Helmholtz Resonance Physics

\[f = \frac{v}{2\pi}\sqrt{\frac{A}{V L}}\]
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$4.99 USD
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Meet Hummix, a bottle who sings a low note when someone blows across her neck. The air in the neck bounces like a plug on the spring of air inside, a Helmholtz resonator. A 750 mL bottle hums at roughly 160 Hz, and adding water raises the note. Pixel-art kiss-cut sticker in 2, 3, 4 and 6 inches; equation, symbols and sources in the physics panel below.

Size
Surface

Flat $6 shipping worldwideMade to order, ships in 2–5 business days

Details

Size3″ × 3″

3″ × 3″ kiss-cut sticker.

Shipping

Flat $6 shipping on every order, worldwide, whatever's in it.

Delivery times & where we ship

Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

Meet Hummix, a bottle who sings a low note whenever someone blows across her neck.

Air in the neck of a bottle acts like a small plug, and the larger body of air inside acts like a spring. Push the plug in and the air inside is squeezed, so it pushes back. The plug overshoots and bounces in and out. Blowing across the opening keeps this bouncing going, and you hear it as a steady hum.

The frequency is f = (v/2π)√(A/(VL)), where A and L are the area and length of the neck and V is the volume inside. For a 750 mL bottle with a neck 2 cm across and about 5 cm long, this gives roughly 160 Hz, a low hum.

Pour in some water and the air volume shrinks, so the note goes higher.

The same resonance shapes the sound of guitars and violins, booms in a car with one window open, and is used in speaker ports to boost the bass.

Equations

\[f = \frac{v}{2\pi}\sqrt{\frac{A}{V L}}\]
SymbolMeaningUnit
\(f\) resonant frequency \(\mathrm{Hz}\)
\(v\) speed of sound in air \(\mathrm{m/s}\)
\(A\) cross-sectional area of the neck \(\mathrm{m²}\)
\(V\) volume of air in the body \(\mathrm{m³}\)
\(L\) effective length of the neck \(\mathrm{m}\)

Sources

  1. Wikipedia — Helmholtz resonance
  2. OpenStax University Physics Vol. 1 — Speed of Sound

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