Sine-wave Speech Demonstrates An Auditory One-way Door

October 7, 2023 by Donald Papp 40 Comments

Sine-wave speech can be thought of as a sort of auditory illusion, a sensory edge case in which one’s experience has a clear “before” and “after” moment, like going through a one-way door.

Sine-wave speech (SWS) is intentionally-degraded audio. Here are the samples, and here’s what to do:

Choose a sample and listen to the sine-wave speech version (SWS). Most people will perceive an unintelligible mix of tones and beeps.
Listen to the original version of the sentence.
Now listen to the SWS version again.

Most people will hear only some tones and beeps when first listening to sine-wave speech. But after hearing the original version once, the SWS version suddenly becomes intelligible (albeit degraded-sounding).

These samples were originally part of research by [Chris Darwin] into speech perception, but the curious way in which one’s experience of a SWS sample can change is pretty interesting. The idea is that upon listening to the original sample, the brain — fantastic prediction and learning engine that it is — now knows better what to expect, and applies that without the listener being consciously aware. In fact, if one listens to enough different SWS samples, one begins to gain the ability to understand the SWS versions without having to be exposed to the originals. In his recent book The Experience Machine: How Our Minds Predict and Shape Reality, Andy Clark discusses how this process may be similar to how humans gain fluency in a new language, perceiving things like pauses and breaks and word forms that are unintelligible to a novice.

This is in some ways similar to the “Green Needle / Brainstorm” phenomenon, in which a viewer hears a voice saying either “green needle” or “brainstorm” depending on which word they are primed to hear. We’ve also previously seen other auditory strangeness in which the brain perceives ever-increasing tempo in music that isn’t actually there (the Accelerando Illusion, about halfway down the list in this post.)

Curious about the technical details behind sine-wave speech, and how it was generated? We sure hope so, because we can point you to details on SWS as well as to the (free) Praat software that [Chris] used to generate his samples, and the Praat script he wrote to actually create them.

Creating An Automated Hydrogen Generator At Home

October 6, 2023 by Maya Posch 34 Comments

Everyone and their pet hamster probably knows that the most common way to produce hydrogen is via the electrolysis of water, but there are still a number of steps between this elementary knowledge and implementing a (mostly) automated hydrogen generator. Especially if your end goal is to create liquid hydrogen when everything is said and done. This is where [Hyperspace Pirate]’s latest absolutely not dangerous project commences, with the details covered in the recently published video.

Automated hydrogen generator setup, courtesy of [Hyperspace Pirate]'s dog drinking bowl. — Automated hydrogen generator setup, courtesy of [Hyperspace Pirate]’s dog drinking bowl.

Since electrolysis cannot occur with pure water, sodium hydroxide (NaOH) is used in the solution to provide the ions. The electrodes are made of 316 stainless steel, mostly because this is cheap and good enough for this purpose. Although the original plan was to use a stacked series of electrodes with permeable membranes like in commercial electrolysers, this proved to be too much of a hassle to seal up leak-tight. Ergo the demonstrated version was attempted, where an upturned glass bell provides the barrier for the produced hydrogen and oxygen. With this system it’s easy to measure the volume of the produced hydrogen due to the displaced water in the bell.

Once enough hydrogen gas is produced, a vacuum pump is triggered by a simple pair of electrodes to move the hydrogen gas to a storage container. Due to hydrogen embrittlement concerns, an aluminium tank was used rather than a steel one. Ultimately enough hydrogen gas was collected to fill a lot of party balloons, and with the provided information in the video it should be quite straightforward to reproduce the system.

Where the automation comes into play is with a control system that monitors for example how long the vacuum pump has been running, and triggers a fail safe state if it’s more than a set limit. With the control system in place, [Hyperspace Pirate] was able to leave the hydrogen generator running for hours with no concerns. We’re hopeful that his upcoming effort to liquify this hydrogen will be as successful, or the human-rated blimp, or whatever all this hydrogen will be used for.

Continue reading “Creating An Automated Hydrogen Generator At Home” →

Metamaterial Enables Topological Pumping Of Elastic Surface Waves

October 3, 2023 by Maya Posch 3 Comments

Although it is generally assumed that surface elastic waves (vibrations) — such as those of earthquakes — will travel mostly unimpeded until their energy dissipates, there are ways to ‘steer’ this energy using metamaterials.

Time response of the topological surface wave transport.(A to C). The magnitude of total displacement field at 0.5 ms, 2.5 ms, and 4 ms, respectively. A 50-cycle tone burst signal centered at 41.88 kHz is simulated on the bottom supercell. (Wang et al., 2023) — Time response of the topological surface wave transport.
(A to C). The magnitude of total displacement field at 0.5 ms, 2.5 ms, and 4 ms, respectively. A 50-cycle tone burst signal centered at 41.88 kHz is simulated on the bottom supercell. (Wang et al., 2023)

A recent study by [Shaoyun Wang] and colleagues in Science Advances details how a carefully modelled grouping of columns creates what is termed a synthetic dimension. In their experimental setup, it is demonstrated how an applied wave is guided across the metamaterial, rather than spreading out the way which we would expect to see in conventional materials.

Interestingly, in the paper it is also demonstrated how the same technique can be used to create a wave-splitter that diverts the wave energy in two distinct directions. Due to the innate resistance of this type of structure to defects, manufacturing it is not too complicated.

In this experiment the metamaterials were milled out of a block of aluminium on a CNC mill, which makes it seem eminently realistic that it could be scaled up and translated to other applications. Conceivably annoyances like vibrations from road traffic and heavy machinery, all the way up to the destructive energies of earthquakes could one day be reduced, redirected or even extinguished using structures as demonstrated here.

Femtosecond Laser Clones Itself In Glass

October 3, 2023 by Maya Posch 4 Comments

When researchers at the Galatea laboratory in Switzerland set out to create a femtosecond laser in glass they weren’t certain it was going to work. To be precise, their goal was to create a femtosecond laser cavity using carefully aligned optics. Rather than using the traditional, discrete method, they used a commercial femtosecond laser to carve out the elements of the optical cavity in glass. The choice for glass came down to the low thermal expansion of this material, and it being transparent for the optical frequencies being targeted.

Generic concept of an “all-glass” optical device, with the various stages of fabrication. (Credit: Antoine Delgoffe et al., 2023)

Even after using the existing laser to create the rough laser cavity, the resulting optical mirrors were not aligned properly, but this was all part of the plan.

By also adding slots that created a flexure mechanism, brief laser pulses could be used to gradually adjust the mirrors to create the perfect alignment. During subsequent testing of the newly created laser cavity it was found to be operating as expected. The original femtosecond laser had successfully created a new femtosecond laser.

Perhaps the most tantalizing aspect of this research is that this could enable much faster and ultimately cheaper production of such laser systems, especially once the tedious and currently completely manual mirror alignment procedure is automated. In addition, it raises the prospect of producing other types of optics including splitters and guides in a similar manner.

The measurement results of: (a) RSSI in dBm collected from gateway 2 and (b) soil moisture during the winter period. (Credit: Maja Škiljo et al., 2022)

Using LoRa Nodes As Soil Moisture Sensing Antennas

October 2, 2023 by Maya Posch 9 Comments

Implementation of LoRaWAN-based soil moisture sensing device. (Credit: Maja Škiljo et al., 2022)

Although we generally think of Internet of Things (IoT) and similar devices as things that are scattered around above ground, there are plenty of reasons to also have such devices underground. These so-called IoUT devices are extremely useful when it comes to monitoring underground structures, but communication via radiowaves is obviously impacted when soil is in the way. Although there are ways to get around this, a 2022 paper by Maja Škiljo and colleagues in Sensors covers an interesting way to make use of this signal attenuation property of changing moisture levels in soil.

By quantifying the exact attenuation of the signal received at the gateways, they were able to determine the soil moisture levels around the LoRa node which had been buried at a depth of approximately 14 centimeters. This LoRa node used off-the-shelf components consisting of an ATmega328P-based Arduino Pro Mini and SX1276-based RFM95W LoRa module with a spring antenna.

During experimentation in- and outdoors it was determined that a narrowband, printed (PCB) antenna was optimal for soil moisture sensing purposes. Other than the interesting question of how to keep soil moisture sensing nodes like this powered up over long periods of time (perhaps periodic retrieval to replenish the battery), this would seem to be a very interesting way to monitor the soil moisture levels in something like a field, where each node can provide its own ID and the received signal providing the relevant data in the form of the SNR and other parameters recorded by the gateway.

(Heading image: The measurement results of: (a) RSSI in dBm collected from gateway 2 and (b) soil moisture during the winter period. (Credit: Maja Škiljo et al., 2022) )

Micro Robot Disregards Gears, Embraces Explosions

September 30, 2023 by Donald Papp 18 Comments

Researchers at Cornell University have developed a tiny, proof of concept robot that moves its four limbs by rapidly igniting a combination of methane and oxygen inside flexible joints.

The device can’t do much more than blow each limb outward with a varying amount of force, but that’s enough to be able to steer and move the little unit. It has enough power to make some very impressive jumps. The ability to navigate even with such limited actuators is reminiscent of hopped-up bristebots.

Electronic control of combustions in the joints allows for up to 100 explosions per second, which is enough force to do useful work. The prototype is only 29 millimeters long and weighs only 1.6 grams, but it can jump up to 56 centimeters and move at almost 17 centimeters per second.

The prototype is tethered, so those numbers don’t include having to carry its own power or fuel supply, but as a proof of concept it’s pretty interesting. Reportedly a downside is that the process is rather noisy, which we suppose isn’t surprising.

Want to see it in action? Watch the video (embedded below) to get an idea of what it’s capable of. More details are available from the research paper, as well.

Continue reading “Micro Robot Disregards Gears, Embraces Explosions” →

Building A Human-Sized Pop-Pop Boat

September 29, 2023 by Lewin Day 7 Comments

Pop-pop boats are a neat little science teaching tool that many children end up playing with at some point or other. They’re normally sized to float around a sink or bathtub. [Steve Mould] recently got the opportunity to board a much larger example, sized for an actual human passenger.

The boat belongs to the The AHHAA Science Center in Estonia, along with a smaller model about half the size. Both are fired by propane gas burners to give them some real heat output into the water tank, far beyond what you’d get from little tea light candles. In the case of the larger boat, it uses a series of valves to allow the tank to be filled with water while the rear thrust pipes are closed.

At the larger scale, it’s more easy to visualize the flow out of the boat’s rear outlets. It’s by no means a fast way to get around on the water, with a top speed somewhat less than walking pace. It’s also very loud. Regardless, it’s amusing to see the pop-pop engine work even when scaled up to full size.

If you’re looking for an in-depth explanation of how pop-pop boats work, [Steve Mould] has covered that previously. Video after the break.

Continue reading “Building A Human-Sized Pop-Pop Boat” →