ultrasonic

127 Articles

An AI-generated diagram of the coffee-making process is shown. A filter holds a basket of coffee grounds, which are contained in a paper filter. An ultrasonic transducer vibrates the basket.

Brewing Espresso With Ultrasonic Assistance

June 21, 2026 by 43 Comments

There are as almost as many kinds of coffee as there are of coffee drinkers, with each method for preparing the beverage appealing to a different kind of palate: moka pots, filter coffee, pour-over coffee, French presses, cold brews, espresso, and more produce their own unique flavours by extracting different compounds from the grounds to different degrees. Now, a new method has joined the throng: ultrasonic-assisted extraction, which can produce even an espresso at room temperature.

Espresso is normally made by forcing hot water through tightly-packed, finely-ground coffee beans, quickly producing a concentrated extraction. Its one of the hardest kinds of coffee to consistently make well, since the outcome is influenced by everything from grind size and packing density to temperature, pressure, and more. Ultrasonic agitation helps here by creating cavitation bubbles, which form shock waves as they collapse, breaking open the bean structure and producing small, strong jets of water. The experimental apparatus was built into a modified espresso machine. An ultrasonic transducer delivers vibrations to the basket containing the room-temperature slurry of coffee grounds for two or three minutes.

To quantify the results, the researchers analysed total dissolved solids, extraction yield, pH, colour, volatile components, and caffeine and chlorogenic acid contents. By varying ultrasonic power and grind size, the extraction yield and dissolved solids could be adjusted to closely match traditional espresso or cold-brew coffee. The other metrics had no significant differences, and a survey of 100 coffee drinkers found no preference between this and traditional espresso. When the drinkers tried the cold-brew coffees, they preferred the version made with ultrasonic assistance. The experiment succeeded in its goal of reducing energy consumption: the ultrasonic-assisted coffee took about a quarter as much energy to make.

If you still prefer a more traditional approach, we’ve covered some beautiful espresso machines before, including one made out of motorcycle engine parts.

An ultrasonic transducer with two wires attached to it by alligator clips floats very slightly suspended over a glass surface.

A Different Kind Of Ultrasonic Levitation

April 27, 2026 by 3 Comments

Ultrasonic levitation is by now a familiar trick: one or more ultrasonic transducers create a standing wave, and small objects can be held in the nodes of this standing wave. With a sufficiently large array of transducers, it’s even possible to control the movement of the object. This isn’t the only form of ultrasonic levitation, however, as [Steve Mould] demonstrated with his ultrasonic air hockey table.

This less familiar form of levitation was discovered by [Bob Collins] while working on torpedo guidance systems: when he tried to place a glass lens on an ultrasonic transducer it immediately slid off. He found during further experimentation that an ultrasonic transducer would levitate over any sufficiently flat and smooth surface. It works by trapping a very thin layer of air between the transducer and the smooth surface. When the transducer moves sharply toward the surface, it compresses a layer of air in between, and forces some air out, and the reverse happens while pulling back. However, during the downstroke, the gap through which air can escape is narrower than during the upstroke, and there is more surface-induced drag, meaning that the inflow and outflow of air through a narrow gap isn’t completely equal. At a certain distance, inflow and outflow balance, and the transducer floats on a thin layer of air. Continue reading “A Different Kind Of Ultrasonic Levitation” →

A device rather resembling a megaphone is lying on a table. The handle is made of black plastic. The horn is made of grey plastic, is hexagonal, and is not tapered. At the back of the horn is an array of silver ultrasonic transducers.

Accurately Aiming Audio With An Ultrasonic Array

January 18, 2026 by 36 Comments

When [Electron Impressions] used a powerful ultrasonic array to project a narrow beam of sound toward a target, he described it as potentially useful in getting someone’s attention from across a crowded room without disturbing other people. This is quite a courteous use compared to some of the ideas that occur to us, and particularly compared to the crowd-control applications that various militaries and police departments put directional speakers to.

Regardless of how one uses it, however, the physics behind such directional speakers is interesting. Normal speakers tend to disperse their sound widely because the size of the diaphragm is small compared to the wavelength of the sound they produce; just like light waves passing through a pinhole or thin slit, the sound waves diffract outwards in all directions from their source. Audible frequencies have wavelengths too long to make a handheld directional speaker, but ultrasonic waves are short enough to work well; [Electron Impressions] used 40 kHz, which has a wavelength of just eight millimeters. To make the output even more directional, he used an array of evenly-spaced parallel emitters, which interfere constructively to the front and destructively to the sides. Continue reading “Accurately Aiming Audio With An Ultrasonic Array” →

A rough, pixelated outline of a bird is shown in white in the top of the image. A red replica of this image is shown in a spectrogram in the lower half of the image. A smaller picture-in-picture display in the bottom right of the image shows a man sitting in a studio.

AVIF: The Avian Image Format

July 29, 2025 by 35 Comments

Humans have long admired the sound of birdsong, but to fully appreciate how technically amazing it is, you need an ultrasonic microphone. [Benn Jordan] recently created a video about using these microphones to analyze a collection of bird calls, even training a starling to repeat an image encoded in sound, and has some recommendations for amateurs wanting to get started in computational ornithology.

In the first part of the video, [Benn] set up automated ultrasonic recorders at home, made recordings in Florida and rural Georgia, and visited a starling named “The Mouth,” famous for his ability to mimic human sounds. As a demonstration of his abilities, [Benn] drew a simple bird shape in a spectrogram, converted it into sound, and played it for The Mouth several times. Initially, it didn’t seem that the starling would repeat it, but while he was analyzing his recordings later, [Benn] found the characteristic bird shape. The Mouth had been able to repeat it almost pitch-perfectly. It was in this analysis that the ultrasonic microphones showed their worth, since they were able to slow down the birds’ complex vocalizations enough to detect their complex structures without losing audio quality. Continue reading “AVIF: The Avian Image Format” →

High Frequency Food: Better Cutting With Ultrasonics

March 21, 2025 by 36 Comments

You’re cutting yourself a single slice of cake. You grab a butter knife out of the drawer, hack off a moist wedge, and munch away to your mouth’s delight. The next day, you’re cutting forty slices of cake for the whole office. You grab a large chef’s knife, warm it with hot water, and cube out the sheet cake without causing too much trauma to the icing. Next week, you’re starting at your cousin’s bakery. You’re supposed to cut a few thousand slices of cake, week in, week out. You suspect your haggardly knifework won’t do.

In the home kitchen, any old knife will do the job when it comes to slicing cakes, pies, and pastries. When it comes to commercial kitchens, though, presentation is everything and perfection is the bare minimum. Thankfully, there’s a better grade of cutting tool out there—and it’s more high tech than you might think.

Continue reading “High Frequency Food: Better Cutting With Ultrasonics” →

Setting The Stage For Open Source Sonar Development

January 24, 2025 by 19 Comments

At Hackaday, we see community-driven open source development as the great equalizer. Whether it’s hardware or software —  if there’s some megacorp out there trying to sell you something, you should have the option to go with a comparable open source version. Even if the commercial offering is objectively superior, it’s important that open source alternatives always exist, or else its the users themselves that end up becoming the product before too long.

So we were particularly excited when [Neumi] wrote in to share his Open Echo project, as it contains some very impressive work towards democratizing the use of sonar. Over the years we’ve seen a handful of underwater projects utilize sonar in some form or another, but they have always simply read the data from a commercial, and generally expensive, unit. But Open Echo promises to delete the middle-man, allowing for cheaper and more flexible access to bathymetric data.

Continue reading “Setting The Stage For Open Source Sonar Development” →

Hacked Ultrasonic Sensors Let You See With Sound

December 6, 2024 by 13 Comments

If you want to play with radar — and who could blame you — you can pretty easily get your hands on something like the automotive radar sensors used for collision avoidance and lane detection. But the “R” in radar still stands for “Radio,” and RF projects are always fraught, especially at microwave frequencies. What’s the radar enthusiast to do?

While it’s not radar, subbing in ultrasonic sensors is how [Dzl] built this sonar imaging system using a lot of radar principles. Initial experiments centered around the ubiquitous dual-transducer ultrasonic modules used in all sorts of ranging and detection project, with some slight modifications to tap into the received audio signal rather than just using the digital output of the sensor. An ESP32 and a 24-bit ADC were used to capture the echo signal, and a series of filters were implemented in code to clean up the audio and quantify the returns. [Dzl] also added a downsampling routine to bring the transmitted pings and resultant echoes down in the human-audible range; they sound more like honks than pings, but it’s still pretty cool.

To make the simple range sensor more radar-like, [Dzl] needed to narrow the beamwidth of the sensor and make the whole thing steerable. That required a switch to an automotive backup sensor, which uses a single transducer, and a 3D printed parabolic dish reflector that looks very much like a satellite TV dish. With this assembly stuck on a stepper motor to swivel it back and forth, [Dzl] was able to get pretty good images showing clear reflections of objects in the lab.

If you want to start seeing with sound, [Dzl]’s write-up has all the details you’ll need. If real radar is still your thing, though, we’ve got something for that too.

Thanks to [Vanessa] for the tip.