sound

91 Articles

Mapping The Sound Field Of An Acoustic Levitator

March 12, 2026 by 4 Comments

Sound! It’s a thing you hear, moreso than something you see with your eyes. And yet, it is possible to visualize sound with various techniques. [PlasmatronX] demonstrates this well, using a special scanning technique to visually capture the sound field inside an acoustic levitation device. 

If you’re unfamiliar, acoustic levitation devices like this use ultrasound to create standing waves that can hold small, lightweight particles in mid-air. The various nodes of the standing wave are where particles will end up hovering. [PlasmatronX] was trying to calibrate such a device, but it proved difficult without being able to see what was going on with the sound field. Hence, the desire to image it!

Imaging the sound field was achieved with a Schlieren optical setup, which can capture variations in air density as changes in brightness in an image. Normally, Schlieren imaging only works in a two-dimensional slice. However, [PlasmatronX] was able to lean on computed tomography techniques to create a volumetric representation of the sound field in 3D. He refers to this as “computerized acoustical tomography.” Images were captured of the acoustic levitation rig from different angles using the Schlieren optics rig, and then the images were processed in Python to recreate a 3D image of the sound field.

We’ve seen some other entertaining applications of computed tomography techniques before, like inspecting packets of Pokemon cards. Video after the break.

Continue reading “Mapping The Sound Field Of An Acoustic Levitator” →

The Music Of The Sea

December 22, 2025 by 8 Comments

For how crucial whales have been for humanity, from their harvest for meat and oil to their future use of saving the world from a space probe, humans knew very little about them until surprisingly recently. Most people, even in Herman Melville’s time, considered whales to be fish, and it wasn’t until humans went looking for submarines in the mid-1900s that we started to understand the complexities of their songs. And you don’t have to be a submarine pilot to listen now, either; all you need is something like these homemade hydraphones.

Continue reading “The Music Of The Sea” →

Airbags, And How Mercedes-Benz Hacked Your Hearing

October 6, 2025 by 43 Comments

Airbags are an incredibly important piece of automotive safety gear. They’re also terrifying—given that they’re effectively small pyrotechnic devices that are aimed directly at your face and chest. Myths have pervaded that they “kill more people than they save,” in part due a hilarious episode of The Simpsons. Despite this, they’re credited with saving tens of thousands of lives over the years by cushioning fleshy human bodies from heavy impacts and harsh decelerations.

While an airbag is generally there to help you, it can also hurt you in regular operation. The immense sound pressure generated when an airbag fires is not exactly friendly to your ears. However, engineers at Mercedes-Benz have found a neat workaround to protect your hearing from the explosive report of these safety devices. It’s a nifty hack that takes advantage of an existing feature of the human body. Let’s explore how air bags work, why they’re so darn loud, and how that can be mitigated in the event of a crash.

Continue reading “Airbags, And How Mercedes-Benz Hacked Your Hearing” →

Back To The 90s On Real Hardware

August 22, 2025 by 8 Comments

As the march of time continues on, it becomes harder and harder to play older video games on hardware. Part of this is because the original hardware itself wears out, but another major factor is that modern operating systems, software, and even modern hardware don’t maintain support for older technology indefinitely. This is why emulation is so popular, but purists that need original hardware often have to go to extremes to scratch their retro gaming itch. This project from [Eivind], for example, is a completely new x86 PC designed for the DOS and early Windows 98 era.

The main problem with running older games on modern hardware is the lack of an ISA bus, which is where the sound cards on PCs from this era were placed. This build uses a Vortex86EX system-on-module, which has a processor running a 32-bit x86 instruction set. Not only does this mean that software built for DOS can run natively on this chip, but it also has this elusive ISA capability. The motherboard uses a Crystal CS4237B chip connected to this bus which perfectly replicates a SoundBlaster card from this era. There are also expansion ports to add other sound cards, including ones with Yamaha OPL chips.

Not only does this build provide a native hardware environment for DOS-era gaming, but it also adds a lot of ports missing from modern machines as well including a serial port. Not everything needs to be original hardware, though; a virtual floppy drive and microSD card reader make it easy to interface minimally with modern computers and transfer files easily. This isn’t the only way to game on new, native hardware, though. Others have done similar things with new computers built for legacy industrial applications as well.

Thanks to [Stephen] for the tip!

Continue reading “Back To The 90s On Real Hardware” →

Measuring A Well With Just A Hammer And A Smartphone

December 19, 2024 by 38 Comments

What’s the best way to measure the depth of a well using a smartphone? If you’re fed up with social media, you might kill two birds with one stone and drop the thing down the well and listen for the splash. But if you’re looking for a less intrusive — not to mention less expensive — method, you could also use your phone to get the depth acoustically.

This is a quick hack that [Practical Engineering Solutions] came up with to measure the distance to the surface of the water in a residential well, which we were skeptical would work with any precision due to its deceptive simplicity. All you need to do is start a sound recorder app and place the phone on the well cover. A few taps on the casing of the well with a hammer send sound impulses down the well; the reflections from the water show up in the recording, which can be analyzed in Audacity or some similar sound editing program. From there it’s easy to measure how long it took for the echo to return and calculate the distance to the water. In the video below, he was able to get within 3% of the physically measured depth — pretty impressive.

Of course, a few caveats apply. It’s important to use a dead-blow hammer to avoid ringing the steel well casing, which would muddle the return signal. You also might want to physically couple the phone to the well cap so it doesn’t bounce around too much; in the video it’s suggested a few bags filled with sand as ballast could be used to keep the phone in place. You also might get unwanted reflections from down-hole equipment such as the drop pipe or wires leading to the submersible pump.

Sources of error aside, this is a clever idea for a quick measurement that has the benefit of not needing to open the well. It’s also another clever use of Audacity to use sound to see the world around us in a different way.

Continue reading “Measuring A Well With Just A Hammer And A Smartphone” →

Minichord Wants To Help You Find Rad Chord Progressions

November 28, 2024 by 8 Comments

If you’re good at music theory, you can probably find all the chords and progressions you need just by using your fingers and a suitable instrument. For a lot of musicians, though, remembering huge banks of chords can be difficult, and experimenting with combinations can quickly become tedious and tiring. Enter the minichord, a tiny version of the Omnichord synth designed by [Benjamin] that offers to help out by putting all the chords you need a mere button press away.

The minichord is based around the Teensy 4.0, a capable microcontroller platform if ever there was one. It’s paired with a bunch of tactile buttons which are used to tell the Teensy which chord you desire to play. Various combinations of buttons can be used to play more advanced chords, too. There are potentiometers on board as well for volume control, as well as a touch pad for “strumming” arpeggios and other fine control tasks. An online interface allows modifying the presets onboard, too.

[Benjamin] hopes to get the minichord into production; it’s currently in a Seeedstudio competition that could see that happen, based on likes on the project video. The minichord isn’t the only player in this space, of course. The Orchard synth has been making similar waves this week. We’ve seen [Benjamin’s] work before, too. Video after the break. Continue reading “Minichord Wants To Help You Find Rad Chord Progressions” →

Audio On Pi: Here Are Your Options

August 12, 2024 by 35 Comments

There are a ton of fun Raspberry Pi and Linux projects that require audio output – music players, talking robots, game consoles and arcades, intelligent assistants, mesh network walkie-talkies, and much more! There’s no shortage of Pi-based iPods out there, and my humble opinion is that we still could use more of them.

To help you in figuring out your projects, let’s talk about all the ways you can use to get audio out of a Pi or a similar SBC. Not all of them are immediately obvious and you ought to know the ropes before you implement one of them and get unpleasantly surprised by a problem you didn’t foresee. I can count at least five ways, and they don’t even include a GPIO-connected buzzer!

Let’s rank the different audio output methods, zoning in on things like their power consumption, and sort them by ease of implementation, and we’ll talk a bit about audio input options while we’re at it.

Continue reading “Audio On Pi: Here Are Your Options” →