Tag: Gadgets

Exploring the Boundless Spectrum: The World of Animal Hearing | August 29 2025, 17:56

From my notes as I read Ed Yong’s Immense World—

“..It is known that the range of audible frequencies for animals is different from that of humans, but I didn’t realize just how different. Imagine the highest pitch in the world—it would be just under 20 kHz, as it’s considered the upper limit of the audible range. Both the upper and lower limits tend to decrease with age. Most adults can’t hear sounds over 16 kHz. Anything above 20 kHz we call ultrasound.

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So, it turns out that our closest relatives, chimpanzees, can hear up to 30 kHz, dogs up to 45 kHz, cats up to 85 kHz, mice up to 100 kHz, and moths even up to 300 kHz. Imagine, there are so many high-frequency sounds around us, and how rich their sound world is compared to our limited one. It would be interesting to wear headphones that compress the range from 20-40000 Hz to 20-15000 Hz. Many animals, such as mice, actively use ultrasound for internal communication, beyond the hearing range of their predators.

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And when the topic of ultrasound comes up, it’s impossible not to mention bats with their echolocation. Turns out, it’s a wildly interesting topic.”

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Probably everyone knows that bats successfully hunt in caves, where no light penetrates at all, and they don’t crash into stalactites and stalagmites. There’s an English saying, blind as a bat, but actually, they can see. Some species see better, others worse. But let’s talk about echolocation.

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In general, it’s just radar. The bat screams, the sound bounces off a tree, comes back into its ears, and it gets information about how far away the tree is and whether to slow down or not. But the devil, as they say, is in the details. “Engineering” ones.

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Firstly, high-frequency sound attenuates quickly, so you need to shout very loudly for something to bounce back from a few meters away. Beyond that, bats simply don’t “see.” So, they do indeed shout very loudly, and it’s a directed scream. Specifically, they measured 138 decibels, the sound level of a jet engine if you stand next to it. But in the ultrasonic range.

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Secondly, when they scream so loudly, they need to plug their own ears so as not to kill their sensitive apparatus. It turned out that they have special muscles that block the inner ear during the scream.

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Thirdly, both they and their prey are on the move, very fast and erratic. Meanwhile, the speed of sound is about 343 meters per second. The bat’s brain must calculate the difference between the signal and the echo, taking into account both its own movement through space and the movement of the prey. It turned out that the bat’s vocal muscles can contract up to 200 times a second. Moreover, the frequency depends on the phase of the hunt. 200 times—that’s the final phase, when the moth is right in front of the nose, and tiny movements need to be tracked.

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Fourthly, the bat’s brain also has to cope with creating interference between what was shouted out two moments ago and what was shouted out a moment ago. Considering that the sound can echo off the far wall and the near branch. Plus there are waves from the cries of other bats, and they’re usually very numerous in caves. To manage this, they seem to throw a bit different modulation, plus this musculature allows them to “fire” very short pulses—a few milliseconds—and to renew pulses at their own frequency through very short intervals. Imagine what kind of computer in their brains performs the inverse Fourier transform.”

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So, all this works pretty well in small groups. But for example, the Brazilian free-tailed bats live in groups of millions. Really, together 20 million mouths shout something and wait for their echo from the walls and each other. You can’t just pick modulation and frequencies that easily, but somehow they manage. Not perfectly, and if they gather in a really big bunch in the cave, then they perform their commute to the hunt and back to the cave “by memory” – probably due to issues with echolocation. When a “door” was placed at the entrance to the cave, a bunch of bats crashed into it.

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Fifth, consider how they determine distance. It’s necessary to calculate the difference between the signal sent and the signal received (amid a bunch of noise from other bats), and for hunting, it needs to be calculated very precisely. And sound of course isn’t light, but 343 meters per second is also a lot. So studies have shown that bats can recognize differences as little as 1-2 millionths of a second, which allows them to determine distance to fractions of a millimeter. In other words, our eyes are significantly less accurate than their ears.

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Plus, a moth is actually a fairly complex 3D creation that reflects sound differently with its different parts. Otherwise, bats would eat everything that moves. They recognize. In complete darkness. A mouse’s scream contains a whole palette of frequencies, which reflect differently off parts of a moth, and the mouse’s brain somehow manages to translate this into a coherent picture. Moreover, for each of the constituent frequencies, the delay will be its own.

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Then, all this information is layered over time. Roughly speaking, a snapshot from one point is combined with a snapshot from a point a half meter to the right, then from a point half a meter forward, and so on many, many times, which enhances “sharpness” and detail. Overall, it’s the same with us – we only see the spot in front of us clearly while the rest is constructed by the brain. But the brain of a bat weighs 1-2 grams against our half kilogram.

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Think about it, you’re flying with such a built-in radar, and in front of you are two branches at the same distance, which produce essentially the same echo for their ears. And to distinguish them and understand that it’s not one object but two, you really need an advanced brain.

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So, they send pulses lasting 1-20 ms, plus longer pauses between pulses. The pulses are complex in terms of frequencies, so such bats are called frequency modulation (FM) bats. But there are about 160 species that have a much longer cry—many tens of milliseconds but with short pauses, and instead of a complex gamma of frequencies, these use a pure “note.” These bats are called CF—constant frequency. So here’s the thing with these bats—there’s a problem with the Doppler effect, which is an increase in frequency as the distance decreases. Since their brain is tuned to a strict frequency, like 87 kHz for example, they might lose their prey if the echo that reaches their ears is shifted in frequency. And what they do—they shout at a sound speed lower, so that after the Doppler effect it arrives at the correct frequency for the brain.”

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Incidentally, their radar has two modes—forward and downward, the echoes from which are processed separately. The downward radar provides information about position in space, and the forward radar—about the position in space of the prey.

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When I researched the subject, I found that yes, after 20 kHz humans hear nothing, with one exception—frequencies of 2.4 GHz and 10 GHz, which actually belong to the microwave range. Yes, humans can “hear” these frequencies, but not with the ear, but “hear.” This phenomenon is called the microwave auditory effect or the Frey effect. Initially, this effect was registered by people working near radars during World War II, and the sounds they perceived were not heard by others. It turned out that when pulsed or modulated microwave radiation was applied to areas around the cochlea, it was absorbed by the tissues of the inner ear, accompanied by their thermal expansion. In the course of this process, shockwaves are produced, perceived by humans as sound, which no one else hears. It was also discovered that with the appropriate choice of the modulating signal, it is possible to transmit information to a person in the form of individual words, phrases, and other sounds. Depending on the radiation parameters, the sound created in the head can be irritating, cause nausea, and even disable. The volume of the perceived sound can be changed, but acoustic trauma is not possible, as the eardrum does not participate in the process at all. Generally speaking, the method of specifically transmitting sonic messages that are absolutely inaudible to others opens up a whole bouquet of possibilities. I wonder if research is still being conducted on this topic. Google shows that they used to be pretty intense.”

I once published this along with a video, and Facebook reckons that if you publish a video, the text should be one, at most two lines. And in the end, almost no one saw this text. Everyone just watched the video of a bat flying around my apartment 🙂

Inside Apple AirPods: Design, Battery, and Antenna Secrets Revealed | August 23 2025, 01:52

Very interesting video about how Apple Airpods headphones work (in the comments). You can read about it, or you can just like this post and go check out the original video in the comments. It has pictures!

Battery. 6 hours of operation, but the capacity is only 2% of the iPhone battery capacity. “Dead zones” in the battery, which lead to reduced operating time, can occur due to sudden temperature changes or even just dropping the headphones on the floor. There is a very dense “layered cake” made from a couple dozen layers of anode-cathode. Batteries of fake AirPods or cheap analogs are much worse. Physics: Poor packaging means less active material and fewer lithium ions moving with each cycle => reduced energy density and increased internal resistance => more energy is lost as heat => battery wears out faster.

Antenna. It is located in the stem because the human head significantly dampens the signal. But there is little space in the stem. Metal strip antenna, size 2 mm by 10 microns(!). That’s thinner than human hair. At such size, it cannot maintain shape on its own. In other consumer electronics, antennas can be etched on the printed circuit board, but this limits them to two dimensions. For the AirPod stem, there isn’t enough space. Therefore, Apple uses a clever solution. They embedded the antenna in the surface of a molded plastic cylindrical part. There, clever conductive plastic is used, with added metal. A laser engraves the exact shape of the antenna in the form of small channels with a rough surface. Then, this groove is subjected to electroplating, first with copper, then covered with gold to protect against corrosion. As a result, a durable conductive track is formed, which matches the 3D geometry of the molded part, which would be impossible to create using traditional machining methods. The plastic not only structurally supports the antenna. Other components are attached to it, such as the cable wrapping around the stem to connect the antenna to the Bluetooth chip, the pressure sensor in the stem.

Microphone. In AirPods, not electret microphones, but MEMS: a microelectronic” version of the condenser type. Well, actually, this is not only Apple – any modern TWS headphones, unless they are the cheapest ones. That is to say, modern microphones are made using the same technology as types – photolithography, layer by layer, only in this case it’s a mechanical device, with calculated cavities and flexible layers. Separately interesting is how they make the cavities – they make holes through which etching solution penetrates inside and dissolves the sacrificial layers of silicon dioxide.

Because of such microscopic size, there are several microphones. But why more than one microphone is needed? At the bottom of the AirPods, you will see a small mesh that allows air to enter the second microphone. When you talk, your voice reaches both microphones, but not at the same time. With a difference of only a few millimeters, the chip can detect a delay of six microseconds between when your voice reaches each microphone. This is enough to determine where the sound is coming from and focus on it. Since it precisely knows the distance the microphones are from one another, the chip can compare each signal and amplify your voice during calls.

The third microphone is for noise cancellation. It is located right in front of the speaker, inside your ear.

The microphones consume about 130 mA, which would quickly drain the battery if they were always active. That’s why they are only turned on when you make a call or use noise cancellation. But AirPods are always waiting for a Siri request. How is this possible without constantly active microphones? Here’s a clever solution. Inside the part that is in your ear, there is a small sensor—an accelerometer. It’s the same type of sensor used in phones to determine orientation. But here it serves a different purpose. Instead of measuring orientation, it senses vibration. When you talk, your voice moves through your jawbone. And this vibration is detected by the accelerometer. This low-power consumption signal is enough to wake up the system and activate the microphones when it senses you want to activate Siri. Imagine that, eh?

The sound in AirPods is tuned not “by ear,” but based on a scientific model of the “ideal sound” (Harman curve), which describes the combination of frequencies most people find most pleasing. For this, there is a complicated system of calculated vents and meshes — to control the air flow, which prevents the occurrence of unpleasant “humming” or sharp sounds inside the ear canal. The larger the cells — more air passes through, smaller — less. Such is the mesh, visible as black things on the white earphone—I thought it was for beauty. No, this is exactly that mesh. But at the same time, some kind of moisture protection must be made, and here the mesh is porous. It is claimed that there is some sort of nano-coating that repels water.

Bluetooth. Why it is so immune to interference. Turns out, it uses frequency-hopping spread spectrum technology (Frequency Hopping). Bluetooth devices quickly switch between different channels many times a second and adapt accordingly.

Scam Alert: The Bond Ring Energy Hoax Following My Oura Ring Purchase | August 20 2025, 20:01

I had just bought the Oura Ring 4 when Facebook started running scam ads about the first ring that saps your energy for its own survival. My precious!..

Unlocking Smartwatches with Unique Heart Rhythms: A Missed Opportunity? | August 06 2025, 16:43

Why has no one made it so that smartwatches only unlock on the wrist of their owner, reading their unique heartbeat or other biometric data? This is in addition to having the owner’s phone nearby.

Officially, you can’t disable this in the settings of an Apple Watch — Apple intentionally made it such that when you put on the watch for the first time each day, it always requires a code, even if the iPhone is nearby. This is due to security policy: the watch may end up on someone else’s wrist, and the phone may just be nearby.

Moreover, every person has unique heart rhythm patterns, which include, for example, slight variations in the intervals between heartbeats, characteristics of the heart signal shape, and how the heart responds to different stresses. These microscopic differences create a unique picture” of heart rhythm that is difficult to fake or replicate. Watches have quite a lot of time, after being worn and before they are needed unlocked, to collect, process, and decide whether to unlock or not.

DIY Wireless Reaction Game: Building Interactive Button-Based Activities | July 28 2025, 22:26

Who knows their way around electronics? Any recommendations?

I want to make a thing some weekend. A big bulbous button. It lights up – you smash it. The app records the time from when it lights up to when it’s smashed. There might be several buttons and they could be scattered – on walls or the floor. WIRELESS. They might light up randomly – this is controlled by the app (phone or computer). Metrics like average reaction time are calculated on the fly for different understandings of the word ‘average’. For instance, you could place buttons on the ground a few meters apart and invent a moving game for the kids. Or attach them to a wall and smash them with a ball. Basically, it’s a technical question.

How would you do it – dumb buttons on an nRF24L01+ chip or smart buttons on an esp32 microcontroller?

In the first case, every such module listens to the radio: as soon as a command with its ID arrives from the central node, it turns on the light. After the button is pressed, it sends back a “pressed” message. The timer is on the side of the central node. Each button has an Arduino Pro Mini + nRF24L01+, but there will also be a central hub with either nRF24L01+ and Arduino Uno, Mega or ESP32, which collects the data and is connected to the computer (Bluetooth or WiFi).

In the second case, the buttons are connected via Bluetooth (BLE) or WiFi. The brains of the button is the ESP32, which needs to be programmed through a programmer.

Cost-wise, both approaches are roughly the same minus the cost of arcade buttons and 3D printing, somewhere around $10-15 per button.

The Art of Lawn Striping: Creating Light and Dark Patterns with Grass | July 14 2025, 14:42

We constantly drive past fields organized into stripes or checks. I finally found the time to look into how this is done. It’s called lawn striping, and the effect is achieved by bending the blades of grass in different directions.

The direction in which the grass bends determines whether a stripe will be light or dark. When the blades lean away from you, the lawn looks lighter because the light reflects off the broad and long surface of the blade. When the blades lean towards you, the lawn appears darker because you are looking at the tips of the blades (smaller reflective surface) and you see shadows under the grass. Therefore, mowing the lawn in opposite directions (up/down, left/right, north/south, east/west, etc.) creates the greatest contrast between the stripes. Interestingly, since the “color” of the stripe depends on the direction from which you look at it, a light stripe will appear dark if viewed from the opposite side.

This fuss over grass is a very American phenomenon. I overcome my laziness to mow the lawn only when the grass has indecently overgrown (the notion of “indecently overgrown” is also something I adjust each year after receiving tsk-tsk letters from the village administration). My neighbor, however, seems to do it every few days, and I once saw him kneeling in the grass—complaining that someone had dragged something across his lot, dropping some chips in the grass and ruining its perfection. Really, the only thing missing was a pair of scissors in his hands.

Persistent Notifications: The AirPods Pro Annoyance on a Flight | June 26 2025, 12:45

This weird thing appears on the phone and you can’t close it, it just keeps popping up again and again, every second. For about five minutes. It’s almost impossible to use the phone. Turns out, there’s a guy sitting one seat away from me on the plane, opening and closing an AirPods case, chatting with a girl. He’s got nothing better to do with his hands, darn it.

Discover Your Flight Gate Early with This Simple Plane Finder Hack | June 24 2025, 22:08

I just found a lifehack on how to determine your departure gate when it’s not yet displayed on the board. Go to planefinder net, enter your flight, and it shows the tail number of the airplane for that specific departure. Click on the link with the tail number, and it shows where the plane is arriving from—the gate it arrives at is known much earlier than the gate from where the new flight departs. So head to this gate, as it’s almost certain to appear on the board by the time someone gets around to updating it.

Yes, everything will go awry if they change the plane. But it’s very unlikely that the airplane will change, as any replacement has to be the same model otherwise it causes chaos with the already assigned seating, and airplanes are not changed often (although it has happened to me several times). Nonetheless, there’s nothing to do at the airport, and playing the game of guessing the gate is interesting.