Acoustic Engine Harnesses The Power Of Sound

February 21, 2025 by Dan Maloney 33 Comments

If you think sonic booms from supersonic aircraft are a nuisance, wait until the sky is full of planes propelled by up-scaled versions of this interesting but deafening audio resonance engine.

Granted, there’s a lot of work to do before this “Sonic Ramjet” can fly even something as small as an RC plane. Creator [invalid_credentials] came up with the idea for a sound-powered engine after listening to the subwoofers on a car’s audio system shaking the paint off the body. The current design uses a pair of speaker drivers firing into 3D printed chambers, which are designed based on Fibonacci ratios to optimize resonance. When the speakers are driven with a low-frequency sine wave, the chambers focus the acoustic energy into powerful jets, producing enough thrust to propel a small wheeled test rig across a table.

It’s fair to ask the obvious question: is the engine producing thrust, or is the test model moving thanks to the vibrations caused by the sound? [invalid_credentials] appears to have thought of that, with a video showing a test driver generating a powerful jet of air. Downloads to STL files for both the large and small versions of the resonating chamber are provided, if you want to give it a try yourself. Just be careful not to annoy the neighbors too much.

Thanks to [cabbage] for the tip via [r/3Dprinting].

Replacement PCB Replicates Early 80s Modem

February 21, 2024 by Bryan Cockfield 29 Comments

It’s certainly been a few decades, but plenty of us remember a time before widespread access to broadband internet, when connections were generally made over phone lines using acoustic modems. In the 90s these could connect you to AOL and Napster well enough, but in the early 80s the speeds were barely enough to read text as it loaded. A company called Hayes set out to change this with some of the first useful, widely-available modems for the PCs at the time. While they couldn’t keep up with the changing times there’s still a retro community that has these antiques, and to modernize it a bit this drop-in replacement for the PCBs replicates these old modems almost exactly.

The new PCB is equipped with everything needed to get a retro computer online again, including all the ports to connect a computer without any further modifications. It houses a few modern upgrades beyond its on-board processors, though. Rather than needing an actual acoustic coupled phone, this one has an ESP32 which gives it wireless capability. But the replacement PCB maintains the look and feel of the original hardware by replicating the red status LEDs at the front, fitting into the original Hayes cases with no modifications needed at all, and even includes a small speaker through which it can replicate the various tones, handshakes, and other audio cues that those of us nostalgic for this new online era remember quite well.

For those looking for a retro feel without the hassle of getting antique networking equipment functional again, this type of upgrade that preserves the essence of the original hardware is an excellent way of keeping retro computers functional on modern networking equipment. But if you absolutely must get the networking equipment exactly right down to the last patch cable, you might end up having to build your own ISP from scratch.

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Feeling The Heat: Railway Defect Detection

March 28, 2023 by Dan Maloney 29 Comments

On the technology spectrum, railroads would certainly seem to skew toward the brutally simplistic side of things. A couple of strips of steel, some wooden ties and gravel ballast to keep everything in place, some rolling stock with flanged wheels on fixed axles, and you’ve got the basics that have been moving freight and passengers since at least the 18th century.

But that basic simplicity belies the true complexity of a railway, where even just keep keeping the trains on the track can be a daunting task. The forces that a fully loaded train can exert on not only the tracks but on itself are hard to get your head around, and the potential for disaster is often only a failed component away. This became painfully evident with the recent Norfolk Southern derailment in East Palestine, Ohio, which resulted in a hazardous materials incident the likes of which no community is ready to deal with.

Given the forces involved, keeping trains on the straight and narrow is no mean feat, and railway designers have come up with a web of sensors and systems to help them with the task of keeping an eye on what’s going on with the rolling stock of a train. Let’s take a look at some of the interesting engineering behind these wayside defect detectors.

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An acousto-optic tunable filter and laser

Acousto-Optic Filter Uses Sound To Bend Light

September 10, 2021 by Dan Maloney 17 Comments

We all know that light and sound are wave phenomena, but of very different kinds. Light is electromechanical in nature, while sound is mechanical. Light can travel through a vacuum, while sound needs some sort of medium to transmit it. So it would seem that it might be difficult to use sound to modify light, but with the right equipment, it’s actually pretty easy.

Easy, perhaps, if you’re used to slinging lasers around and terms like “acousto-optic tunable filter” fall trippingly from your tongue, as is the case for [Les Wright]. An AOTF is a device that takes a radio frequency input and applies it to a piezoelectric transducer that’s bonded to a crystal of tellurium oxide. The RF signal excites the transducer, which vibrates the TeO₂ crystal and sets up a standing wave within it. The alternating bands of compressed and expanded material within the crystal act like a diffraction grating. Change the excitation frequency, and the filter’s frequency changes too.

To explore the way sound can bend light, [Les] picked up a commercial AOTF from the surplus market. Sadly, it didn’t come with the RF driver, but no matter — a few quick eBay purchases put the needed RF generator and power amplifier on his bench. The modules went into an enclosure to make the driver more of an instrument and less of a one-off, with a nice multi-turn pot and vernier knob for precise filter adjustment. It’s really kind of cool to watch the output beam change colors at the twist of a knob, and cooler still to realize how it all works.

We’ve been seeing a lot of [Les]’ optics projects lately, from homemade TEA lasers to blasting the Bayer filter off a digital camera, each as impressive as the last! Continue reading “Acousto-Optic Filter Uses Sound To Bend Light” →

Piezo Pickup Makes Wax Records Easy To Digitize

June 23, 2021 by Dan Maloney 27 Comments

Sound recording and playback have come a long way in the last century or so, but it’s fair to say there’s still a lot of interesting stuff locked away on old recordings. Not having a way to play it back is partly to blame; finding an antique phonograph that plays old-timey cylinder recordings is pretty hard. But even then, how do you digitize the output of these fragile, scratchy old recordings?

As it happens, [Jan Derogee] is in a position to answer these questions, with an antique phonograph and a bunch of Edison-style wax cylinders with voices and music from a bygone era locked away on them. It would be easy enough to just use the “reproducer” he previously built and set up a microphone to record the sound directly from the phonograph’s trumpet, but [Jan] decided to engineer a better solution. By adding the piezo element from an electronic greeting card to his reproducer, potted with liberal quantities of epoxy and padded with cotton, the piezo pickup was attached to the phonograph arm in place of the original stylus and trumpet. The signal from the piezo element was strong enough to require a shunt resistor, allowing it to be plugged directly into the audio input jack on a computer. From there it’s just an Audacity exercise, plus dealing with the occasional skipped groove.

We appreciate [Jan]’s effort to preserve these recordings, as well as the chance to hear some voices from the past. We’re actually surprised the recording sound as good as they do after all this time — they must have been well cared for.

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A Scientist Made An Artificial Black Hole In The Lab, And You Won’t Believe What Happened Next

March 8, 2021 by Dan Maloney 53 Comments

OK, that was a little click-baity, but then again, so was the announcement this week that a scientist had confirmed Hawking radiation with a lab-grown black hole. It sure got our attention, at least.

As it turns out, the truth is both less and more than meets the eye. The article above was eventually edited to better reflect the truth that, alas, we have not yet found a way to create objects so massive that even light cannot escape them. Instead, physicist [Jeff Steinhauer] and colleagues at the Technion-Israel Institute of Technology have developed an acoustic model of black holes, which is what was used to observe the equivalent of Hawking radiation for the first time. Hawking radiation is the theoretical exception to the rule that nothing makes it out of a black hole and would imply that black holes evaporate over time. The predicted radiation would be orders of magnitude weaker than the background radiation, though, making it all but impossible to detect.

That’s where [Steinhauer]’s sonic black holes come in. In these experiments, phonons, packets of mechanical vibrations that stand in for photons, are trapped in a fast-moving stream of fluid. The point in the stream where its speed straddles the local speed of sound is the equivalent to a real black hole’s event horizon; phonons inside that boundary can never escape. Except, of course, for the sonic equivalent of Hawking radiation, which the researchers found after 97,000 attempts.

When we first stumbled upon this story, we assumed a lab-grown black hole, even an acoustic analog, would take a CERN’s-worth of equipment to create. It turns out to be far simpler than that; [Steinhauer], in fact, built his black hole machine singlehandedly from relatively simple equipment. The experiments do require temperatures near absolute zero and a couple of powerful lasers, so it’s not exactly easy stuff; still, we can’t help but wonder if sonic black holes are within the reach of the DIY community. Paging [Ben Krasnow] and [Sam Zeloof], among others.

[Featured image credit: Nitzan Zohar, Office of the Spokesperson, Technion]

Raspberry Pi Crazy Guitar Rig Turns You Into A Hard ‘N Heavy One-Man Band

October 7, 2020 by Sven Gregori 18 Comments

It’s a common problem: you’re at a party, there’s a guitar, and your plan to impress everyone with your Wonderwall playing skills is thwarted by the way too loud overall noise level. Well, [Muiota betarho] won’t have that issue ever again, and is going to steal the show anywhere he goes from now on with his Crazy Guitar Rig 2.0, an acoustic guitar turned electric — and so much more — that he shows off in three-part video series on his YouTube channel. For the impatient, here’s video 1, video 2, and video 3, but you’ll also find them embedded after the break.

To start off the series, [Muiota betarho] adds an electric guitar pickup, a set of speakers, and an amplifier board along with a battery pack into the body of a cheap acoustic guitar. He then dismantles a Zoom MS-50G multi-effect pedal and re-assembles it back into the guitar itself with a 3D-printed cover. Combining a guitar, effect pedal, amp and speaker into one standalone instrument would make this already an awesome project as it is, but this is only the beginning.

Touch screen and controls closeup — RPi touch screen running SunVox, plenty of buttons, and integrated multi-effect pedal on the left

So, time to add a Raspberry Pi running SunVox next, and throw in a touch screen to control it on the fly. SunVox itself is a free, but unfortunately not open source, cross-platform synthesizer and tracker that [Muiota betarho] uses to add drum tracks and some extra instruments and effects. He takes it even further in the final part when he hooks SunVox up to the Raspberry Pi’s GPIO pins. This allows him to automate things like switching effects on the Zoom pedal, but also provides I/O connection for external devices like a foot switch, or an entire light show to accompany his playing.

Of course, adding a magnetic pickup to an acoustic guitar, or generally electrifying acoustic instruments like a drum kit for example, isn’t new. Neither is using a single-board computer as effect pedal or as an amp in your pocket. Having it all integrated into one single device on the other hand rightfully earns this guitar its Crazy Guitar Rig name.

(Thanks for the tip, [alex]!)

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