Show HN: Eigendrum - Draw any shape and hear what it sounds like as a drum

baselashraf81.github.io

228 pointsBaselAshraf815 days ago100 commentsView on HN

Hi HN, I built Eigendrum, a web tool that solves the 2D wave equation for arbitrary shapes so you can hear what they sound like as drums.

How it works: * Solves -∇²u = λu using finite element analysis (Kφ = λMφ) on a triangle mesh. * Validated to <0.1% error against closed-form solutions for circles (Bessel zeros) and rectangles. * Sound model factors in strike location, Rayleigh damping, and mallet width. * Includes Kac drums I & II to demonstrate identical sound spectra from different geometries. * No frameworks, build steps, or dependencies.

Repo and tests: https://github.com/BaselAshraf81/eigendrum

Happy to answer any questions about the FEM solver or Web Audio setup!

https://eigendrum.com/#p=circle

andai1 day ago

Very cool. Number keys and QWERTYU (or clicking the rows on the right) trigger the "modes" in isolation, which are surprisingly microtonal.

Also you can draw your own drums! What! That's so cool

plaguuuuuu1 day ago

there's an amazing video on youtube about how metal bar/gong instruments (like gamelans) have different overtones, and regular western intervals instead of being consonant (like with vibrating strings) are dissonant - even perfect 5ths - and a totally different set of intervals are consonant (slendro and pelog tunings are a bit different for this reason).

thinking about it, each drum here would have totally different ideal scales to the others.

this is cool.

g6taa1 day ago

Do you have a hint on how to find that video?

telotortium1 day ago

It’s “The Physics of Dissonance”: https://youtube.com/watch?v=tCsl6ZcY9ag

andai23 hours ago

Wow, thanks for sharing.

The video shows this tool, which has a 3D harmony/dissonance explorer, which can be used as a makeshift musical insturment.

https://aatishb.com/dissonance/

g6taa1 hour ago

Thank you!

olelele21 hours ago

A friend told me that a Dutch university ordered a custom gamelan tuned chromatically. It was a total failure and sounds terrible. The gamelan are made one by one w the oldest member of the group making his first and everyone tuning theirs from his down in turn, IIRC.

Jeff_Brown1 day ago

I love it. I wish I could select materials.

tanderson921 day ago

Selecting different materials would not change much. Call the frequencies \lambda_1, \lambda_2, \lambda_3...

You can prove that changing the material has no effect on the relative frequencies: \lambda_2 / \lambda_1, \lambda_3 / \lambda_1, etc. are completely independent of the material.

The shape is the determining factor; changing the materials (and hence the wave speed) just dilates the whole spectrum.

BaselAshraf811 day ago

There's actually a "ring-out" slider and a "mallet" width slider under the drum already.

Ring out controls how fast the higher modes decay (basically stiff vs soft material), The mallet width controls how many modes a strike can even reach, since a real mallet can't drive the high frequency ones very hard.

No labeled presets like "wood" or "metal" though, just raw sliders. Would be a fun addition if someone wants to map a few physically sensible combos to buttons. PRs Welcome!