YOU CAN BUILD THE RIG THAT MAKES SOUND VISIBLE IN THE AIR
A telescope mirror, a razor blade and a strobed LED turn invisible 40 kHz sound waves into visible ripples in the air.
by PlasmatronX
ScienceWorkshop
Built withRaspberry Pi3D printing
- difficulty
- ●●●●○
- time
- a weekend-plus
- license
- MIT
- repo
- repo ACTIVE13 stars
●●●●○ · a weekend-plus · MIT · 13 stars · repo ACTIVE
WHAT YOU’LL NEED
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COMPAREE VERDICT
This is a workshop schlieren imaging setup that makes ultrasonic sound waves visible by bending light through density changes in air. The physics is elegant and the footage is striking, but the repository assumes you already know how schlieren optics work. There are no assembly instructions, no BOM, and no guide to aligning the mirror, blade and camera on the same optical axis — that last part is where most first builds fail. The printed parts hold things in place, but getting the cut-off wire exactly at the mirror's focus and the LED timed to freeze a 40 kHz wave requires patience and a way to measure what you cannot see. The creator's own comparison figure is over 20,000 dollars for a professional system, and this build offers a path to the same physics for the cost of the mirror and a Pi. If you have built optics rigs before or are prepared to iterate on alignment for several evenings, this is a rare chance to image sound. If you have never centred a parabolic mirror or tuned a strobe to a waveform, expect a steep learning curve with no scaffolding.
IN THE REPO
GOOD TO KNOW
- —Thirteen STL parts for 3D printing (mirror mount, clip, thumb screw and wall bracket; slot holder and sliders for the razor-blade light-source slit; LED and camera holders) plus FreeCAD source files.
- —Python code for the Raspberry Pi timing and strobe sync is in the repository.
- —No bill of materials, no assembly guide, no optical alignment procedure.
- —You need an eight inch Newtonian telescope mirror, a razor blade, a 40 kHz ultrasonic transducer, an overdriven LED, a gate driver, and a Raspberry Pi 4 (explicitly not the Pi 5).
- —The creator wrote the Python with Google Gemini and says so openly in the video description.
- —MIT licence, no restrictions on commercial use.
Parts to buy
8 itemsFrom our check of the build. Exact quantities and part numbers are in the creator’s BOM.
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
Videos
PlasmatronX's video on the build: how the rig turns 40 kHz sound waves into visible ripples.
More builds like this
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Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the GitHub repository (Contains the STL files, FreeCAD sources, and Python code. No assembly or alignment guide.)
- 2.Source the eight inch Newtonian mirror first(This is the primary cost and the component that sets the optical path length for everything else.)
- 3.Print the thirteen mounting parts(Mirror mount, the slot slider that holds the razor-blade light-source slit, and the LED and camera holders. The parts hold the optics but do not teach you how to align them.)
- 4.Research schlieren alignment procedures independently(The repository does not include this. You need the mirror, razor blade and camera parfocal on the same axis or you will see nothing.)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
KNOWN ISSUES
- The repository contains the mechanical parts but no guidance on optical alignment — the single hardest part of a schlieren setup. If you have never aligned a telescope mirror with a light source and knife edge before, budget time to learn this separately.
- The creator specifies a Raspberry Pi 4, explicitly not the Pi 5. Check the Python code for GPIO or timing dependencies before substituting.
- No bill of materials means you are reverse-engineering the shopping list from the description and the STL file names. The eight inch mirror is the obvious anchor; the LED driver and transducer specs are not stated.
- The strobe LED is overdriven through a gate driver — this is not a plug-and-play LED, and there is no schematic for the driver circuit. You need to design or source that part yourself.
- The cut-off at the focal point (the creator uses a thin wire about 3.2 m from the mirror) must sit exactly at the mirror's focus; a millimetre off and the image collapses. The printed slider adjusts the razor-blade slit of the light source, not the cut-off, and nothing in the files measures where the focus is.
- Schlieren imaging is sensitive to vibration and air currents. The printed parts are a mount, not an optical bench. Expect to add mass or damping if your workshop has airflow.
Can I use a different size mirror?
The eight inch figure sets the focal length and the mechanical design of the printed mount. A different mirror means redesigning the CAD or building an adjustable rig.
What is the actual parts cost?
No BOM or cost is published. The mirror is the main expense; add a Raspberry Pi 4, a 40 kHz transducer, an LED with a gate driver, a modified audio amplifier, a razor blade and a camera.
Do I need prior optics experience?
The repository assumes it. Schlieren alignment is not intuitive and there is no tutorial here. If you have never centred a mirror or found a focal point, this will be a research project before it is a build.
Can I see sound waves other than 40 kHz ultrasonics?
The code drives the transducer at a configurable frequency (40 kHz by default) and fires a 10 µs LED flash synchronised to the wave for each camera frame, which freezes the pattern. Other frequencies are a setting in config.py, but the creator only demonstrates 40 kHz ultrasound.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
The creator's own figure for a professional schlieren system is upwards of 20,000 dollars — this build offers the same physics for the cost of a mirror and a Pi. Have you aligned schlieren optics before, and if so, what did you wish someone had told you first?
PlasmatronX
PlasmatronX built this schlieren rig in a workshop to image ultrasonic sound waves and published the mechanical design and timing code under the MIT licence. The creator states openly that the Python was written with the help of Google Gemini and gives a comparison figure of over 20,000 dollars for a professional schlieren system.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM1mo agoedited
Practical notes from our verification: the GitHub repository contains thirteen STL files, three FreeCAD sources and the Python timing code (which uses the pigpio library), but no BOM, no schematic for the overdriven LED driver and no optical alignment procedure. The parts list and the key requirements are in the video description instead: an 8-inch Newtonian telescope mirror, an overdriven LED with a gate driver, and a Raspberry Pi 4 — the creator says explicitly not the Pi 5 — with the Python written with Google Gemini. The single biggest gap is alignment guidance: getting the mirror, razor blade and camera aligned is where most first schlieren builds fail, and this repository assumes you already know how. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.