Why you can hear the temperature of water(nytimes.com)
nytimes.com
Why you can hear the temperature of water
https://www.nytimes.com/2024/05/09/science/hot-water-sound-cold.html
149 comments
This is something I noticed as a kid. We had a creek in our backyard, which,depending on the temperature the water would be louder or quieter. This annoyed our dog, which after a number of times caused me to notice. Running water is louder and much more sharp when it's cold out, and quieter and muffled when it's hot out. In the same way sounds are louder in a colder environment because there's already a low level of ambient energy contained in the air and so the energy disperses much more readily but dissipates much more quickly. Essentially a difference between a quick "crack" and a lingering "whump" in terms of auditory impact. This effect also propagates to solid materials, as cold metals and ceramics transmit sound better than warm ceramics or metals. A church bell quite literally is louder on a cold winter's day.
There is nothing like a small waterfall in a deep snow on a snowy day. All other sound is muffled by the snow cover and further dampened by the falling snow.
But the creek will ring like a bell. You can't hear it until you're almost on top of it. It's higher pitched, and will almost always have a tempo based on the shape of the bed of the falls.
There's a waterfall on our farm. It plays music in January. It's amazing, and no one believes me.
But the creek will ring like a bell. You can't hear it until you're almost on top of it. It's higher pitched, and will almost always have a tempo based on the shape of the bed of the falls.
There's a waterfall on our farm. It plays music in January. It's amazing, and no one believes me.
When I used to bake bread commercially early in the morning, the sound of the HVAC, proofing and baking systems would sound like music to me in concert. I can't tell if I was just hallucinating or what, but something about your experience reminded me of it.
My thought on the general "loudness" of cold months was due to reduced noise blocking or absorbing greenery like tree leaves, grass, etc. Which is then altered by a significant snowfall leading to sounds being softened again.
No one here has mentioned temperature inversion [0] which is responsible for a lot of the cold-induced amplification perceived in urban areas. It's quite a fascinating effect.
[0] https://wisconsindot.gov/Documents/doing-bus/eng-consultants...
[0] https://wisconsindot.gov/Documents/doing-bus/eng-consultants...
Cold air is also more dense, less momentous, and can transfer sound energy more efficiently between particles than hot air where the particles are spread out and have their own momentum to maintain rather than the sound's.
The volume of water flow should/would also vary at different times of the year, based on how much the water table is loaded.
Not sure how much of this would be complimentary to the acoustic effect of temperature. Either way, it’s not a simple single-solution explanation.
Not sure how much of this would be complimentary to the acoustic effect of temperature. Either way, it’s not a simple single-solution explanation.
Shouldn't that be an inverse relationship though? Without leaves on the trees you should get less reflection, consequently more of the noise should radiate upwards. Unless you're standing at the other side of a bush/greenery. In that case it definitely absorbs a lot
Lots of small unaligned surfaces, like leaves, scatter the sound and make it interfere with itself. Reflection only makes the sound louder if you have large smooth flatish surfaces.
Ah, I had never considered the interference aspect of sound reflections
I want to make a joke about the "three leaf" problem in acoustics, but I can't find a way to make it funny. Dang.
You made me chuckle. Mission accomplished.
HN is becoming worse and worse everyday :(
Assuming your comment is serious (rather than some quip), I think what we're seeing is differing visions for HN.
One group (me included) enjoys some levity, as long as it's high quality and doesn't get in the way of substantial discussions.
Another group would prefer that HN avoids that entirely.
It mostly seems like a matter of taste / preference, so I'm not sure how we can come to one kind on this, shy of seeing the pro-humour approach clearly hurting the site.
One group (me included) enjoys some levity, as long as it's high quality and doesn't get in the way of substantial discussions.
Another group would prefer that HN avoids that entirely.
It mostly seems like a matter of taste / preference, so I'm not sure how we can come to one kind on this, shy of seeing the pro-humour approach clearly hurting the site.
Usually I see high quality humor make it through. The low-effort Reddit quips get cratered.
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My guess is that frozen terrain is harder, which reflects more sound and makes hitting it noisier.
Could the audible difference be related to varying sound propagation through hot/humid vs cold/dry air?
I don't think so. If I pour hot water into a mug from the kettle, it sounds different with cold water with all the same equipment, room etc
That's my feeling as well. I can hear when the hot water has reached my shower.
I hear the same with my shower, but I'd wager most of the change in sound would be to do with pressure change between the hot and cold source.
That was what I thought at first too. However if it were pressure change, the sound would change when you move the knob, not when the hot water reaches the shower.
Also it's more-or-less the same pressure. It's the cold supply pressure pushing water out of your tank or through your tankless water heater.
Yes, the thermostatic mixing valve is worth understanding- it’s pretty neat.
In most plumbing (at least in the US), there is no difference in pressure between hot and cold because the hot input is the same cold water source.
I turn on the tap in the sink in the bathroom, when waiting for the hot water coming from the cistern. The water in the pipes have cooled down over night. I can hear the difference in the sound when it splashes in the sink, when it is hot. So yeah.
That doesn't surprise me at all. I can tell hot water from cold by how it looks when you pour it, (steam aside).
I'd imagine there may also be a component of sound bouncing off things? I think stuff contracts and expands when it hot or cold? So maybe something that is cold and contracted bounces the sound sharper too? Noooooo clue if that makes any sense, just a bunch of guessing from high school science class.
I think it's this. Sounds are very different based on the temperature and humidity of air. I have a piano at home and the difference is huge and very apparent over time.
Does your piano have a wooden body and sound board?
I'm sure piano techs are all over this topic, but (as a layman) I could imagine the wood's water content being quite relevant.
I'm sure piano techs are all over this topic, but (as a layman) I could imagine the wood's water content being quite relevant.
Piano soundboards are almost always wood. There are a handful of companies that offer carbon fiber soundboards but they are very rare and expensive. As the soundboard gains moisture, it swells and buckles as it has nowhere to go, which makes it louder and also raises the pitch a bit as the strings are pushed a bit. When it gets drier, it goes flat (structurally and musically). If it has been too moist, the wood cells will be compacted and crushed. If it is then dried, it will form cracks as the wooden structure rips itself apart when shrinking again.
A piano soundboard that has been built and kept in a desert for instance will not crack. But if you take a piano from a ~55% humid country and put it in a desert (or overly air-conditioned room! or right in front of a heat radiator!) it will die.
A piano soundboard that has been built and kept in a desert for instance will not crack. But if you take a piano from a ~55% humid country and put it in a desert (or overly air-conditioned room! or right in front of a heat radiator!) it will die.
Does a swollen soundboard noticeably affect pitch even when the piano has a cast-metal harp?
The one harp I've seen up close was in an upright piano I disassembled, and that harp was solid.
The one harp I've seen up close was in an upright piano I disassembled, and that harp was solid.
The harp doesn't actually lie flush on the soundboard; there should be some space in between. The harp is just there to bear the tension of all the strings. The strings are connected to the soundboard via a wooden so called bridge, which is a raised wooden element glued onto the soundboard. It has pins in it which the strings are held against in tension. Bridges have a coating of graphite usually, and combined with the fact that most notes have 3 strings, it creates kind of a blocky pattern.
Here you can see a soundboard, bridge, and hitch pins on the harp. The hitch pins on the harp can be seen up top, then in the middle the bridge and bridge pins, and then below that the soundboard. The hitch pins are located on the opposite side of the keys in a grand, or on the bottom of the piano in an upright. You can see on the right of the image that the harp has a structural element which floats over the bridge, with plenty clearance.
https://www.chuppspianos.com/wp-content/uploads/2014/03/Stei...
P.S. In some pianos you can really hear a metallic undertone produced by the harp, I find Yamaha pianos have a distinct sound that has it.
Here you can see a soundboard, bridge, and hitch pins on the harp. The hitch pins on the harp can be seen up top, then in the middle the bridge and bridge pins, and then below that the soundboard. The hitch pins are located on the opposite side of the keys in a grand, or on the bottom of the piano in an upright. You can see on the right of the image that the harp has a structural element which floats over the bridge, with plenty clearance.
https://www.chuppspianos.com/wp-content/uploads/2014/03/Stei...
P.S. In some pianos you can really hear a metallic undertone produced by the harp, I find Yamaha pianos have a distinct sound that has it.
It’s important, and can change the tuning in spring and fall cycles
most of the US is too dry in the home, and humidification is helpful for all wood in your home - to a point of course. Approx 55% is optimal
Of course in the south it’s the exact opposite - but A/C usually solves the problem.
Every homeowner should monitor their indoor humidity, it’s important for, wood floors, door trims, wood furniture, and our own health. Too much causes mold, too dry is hard on your respiratory system
most of the US is too dry in the home, and humidification is helpful for all wood in your home - to a point of course. Approx 55% is optimal
Of course in the south it’s the exact opposite - but A/C usually solves the problem.
Every homeowner should monitor their indoor humidity, it’s important for, wood floors, door trims, wood furniture, and our own health. Too much causes mold, too dry is hard on your respiratory system
Absolutely not. I first noticed this when visiting Iceland. The hot streams bubbling out of the ground sounded the same as boiling hot water being poured from a kettle, not the kind of cold-water stream sound you'd normally expect in the north in winter.
You can try it yourself. Take two identical kettles, boil the water in each of them and pour it somewhere. Obvious difference.
You can try it yourself. Take two identical kettles, boil the water in each of them and pour it somewhere. Obvious difference.
My piano has a Dammp-Chaser automatic humidifier and dehumidifier system that works well. My piano tech uses a moisture meter to check the soundboard at tuning time and the wood’s moisture has been fairly stable for more than two decades.
That is definitely a thing, but I can tell when the hot water arrives at the bathroom tap by the sound of the water hitting the bowl. So it’s the water too, I’m pretty certain.
Thank you for the great anecdote and explanation, it was fun an very illustrative to visualize the concepts while reading your comment
The video is also excellent.
https://youtu.be/9w3Zl3KBDpI
https://youtu.be/9w3Zl3KBDpI
The intro was hilarious! Thank you :)
You controlled for the volume / depth of water, which for the same mass would be greater when warmer, and the resulting changed interaction with objects ...?
I wonder how well it maps to notions of a “cold reverb” or “warm synth” in music production.
As the article mentions, most people know how to tell the difference by sound but if you were to ask them they would say no, it's impossible.
That just makes me wonder how many other things there are that people subconsciously learns, without it ever becoming obviously noticeable for them?
That just makes me wonder how many other things there are that people subconsciously learns, without it ever becoming obviously noticeable for them?
AC electricity on painted metal objects can be felt by sweeping fingertips, even though there's no current path.
You're absolutely right that people ignore whole lot going on around them in terms of sound, smell etc.
You're absolutely right that people ignore whole lot going on around them in terms of sound, smell etc.
I have felt this (?) often. Dragging fingers over a (metal) Mac Mini, some random laptop, a metal keyboard. Presumably this feeling triggers already at low power levels, otherwise I'd probably be dead.
This is because the device is using an isolated, ungrounded switched-mode power supply to convert mains voltage efficiently and using small, cheap and light components. There is a small capacitance (and extremely high resistance), between the primary and secondary windings of the transformer in the SMPS. An SMPS switches at 100s of kHz, and with this virtual capacitor inside the transformer you couple the high frequency switching into a 100kHz+ voltage noise and this would radiate out along the power conductors and your product fails its electromagnetic emissions certification. Now you can't sell it, and this is usually a problem. It might also interfere with other devices like pacemakers or fire alarms or phone signals or whatever, but it's the not being able to sell it that will really upset your boss. Bloody interfering big-state regulators, can't even blast EM radiation in your own customers' homes. So you have to fix it.
To counteract the noise, you attach a (special, you'll see "Y") capacitor between the primary and secondary sides, right next to the transformer. Now that high frequency noise sees an "easy" short-circuit and it is contained in a small loop within the power supply, not leaking out into the outside world. This needs to be much larger than the (very small) transformer capacitance so it dominates that system.
The downside of this is that now you have an appreciable capacitance between the primary and secondary side. In a grounded system, you connect the primary side of that big capacitor to ground and everything is fine. In an ungrounded system, you can only connect it to something referenced to one of the two wires you have: line or neutral. This means that a small current will flow into the capacitor from each side at line frequency (50 or 60Hz) and the secondary side, connected to the case, will float at some appreciable fraction of mains voltage. You, a damp meatsack, prodding the secondary side with your fleshy protruberances, have capacitance as well. So when you touch this case, that's floating at AC voltage around 100-200V (depends where you are in the world) there's a small current that flows between you and the case as well as the charge flows back and forth. This is what you feel via your nerves, which can detect miniscule currents in this range. Because the capacitors linking you to the mains are, in an absolute sense, small (though far larger than the transformer capacitance), the current is limited to a small amount, far under a milliamp. Actually this would still happen without the bigger capacitor, as there's already some capacitance there, but it could only provide an imperceptible current even to the bio-miracle of the human nervous system. So you have to balance EMI reduction (more capacitance better) against this sensation (more capacitance makes it more noticeable and eventually with a really huge capacitance it would be its own safety hazard).
Why a special capacitor? Well, if were to fail to a short between primary and secondary, now your isolated case is not isolated, it's connected directly to the mains supply and there's no earth wire to dump current to and blow the RCD. So if it didn't immediately blow the fuse (and even then, it needs many 10s of amps to do that to the whole circuit if you don't have fused sockets or plugs in your country, and even then it can also set itself and things nearby on fire without blowing a fuse using only an amp or two if you're unlucky) because it's sitting on, say, metal earthed desk, it's now still floating at mains voltage. However, now it won't deliver microamps, it can deliver a lot more though that carbonised previously-a-capacitor-now-a-small-resistor. If you touch it and have a decent connection to ground, instead of the interference with pacemakers, it can become a turbocharged pacemaker, but your heart doesn't work so well at 50/60Hz and may object to this by going on strike. Regulators for some reason think this is a problem, so you use a special safety capacitor called a "Y" or "X" type, depending on exactly how you use it, which is designed to satisfy them that you probably won't discontinue anyone's sinus rhythm or burn down a building (even if they've actually consented by buying your product!)
So, while is this not an intentional effect, it's also an calculated aspect of the power supply design in the absence of an earth wire and is not a sign of a defect or danger. Other than reminding you that the only thing between you and mains voltage is insulation that's carefully specified, regulated and tested to be safe, for some standardised definition of "safe", of course.
You can also see a much stronger version of this effect with a plasma globe (remember them?). The frequency and the voltage is much higher than 50Hz mains, but the principle is the same: the sphere surface is isolated plastic, there's a very small capacitance to the coil. The current flowing in the low pressure gas in the void is what makes the tendrils. With your with your hand on it, you float at very high voltage and can even produce a tiny sub-millimetre, continuous spark to other objects as the small current flows back and forth into this small capacitance. In retrospect, that plasma globe probably has questionable EMI behaviour when doing that!
To counteract the noise, you attach a (special, you'll see "Y") capacitor between the primary and secondary sides, right next to the transformer. Now that high frequency noise sees an "easy" short-circuit and it is contained in a small loop within the power supply, not leaking out into the outside world. This needs to be much larger than the (very small) transformer capacitance so it dominates that system.
The downside of this is that now you have an appreciable capacitance between the primary and secondary side. In a grounded system, you connect the primary side of that big capacitor to ground and everything is fine. In an ungrounded system, you can only connect it to something referenced to one of the two wires you have: line or neutral. This means that a small current will flow into the capacitor from each side at line frequency (50 or 60Hz) and the secondary side, connected to the case, will float at some appreciable fraction of mains voltage. You, a damp meatsack, prodding the secondary side with your fleshy protruberances, have capacitance as well. So when you touch this case, that's floating at AC voltage around 100-200V (depends where you are in the world) there's a small current that flows between you and the case as well as the charge flows back and forth. This is what you feel via your nerves, which can detect miniscule currents in this range. Because the capacitors linking you to the mains are, in an absolute sense, small (though far larger than the transformer capacitance), the current is limited to a small amount, far under a milliamp. Actually this would still happen without the bigger capacitor, as there's already some capacitance there, but it could only provide an imperceptible current even to the bio-miracle of the human nervous system. So you have to balance EMI reduction (more capacitance better) against this sensation (more capacitance makes it more noticeable and eventually with a really huge capacitance it would be its own safety hazard).
Why a special capacitor? Well, if were to fail to a short between primary and secondary, now your isolated case is not isolated, it's connected directly to the mains supply and there's no earth wire to dump current to and blow the RCD. So if it didn't immediately blow the fuse (and even then, it needs many 10s of amps to do that to the whole circuit if you don't have fused sockets or plugs in your country, and even then it can also set itself and things nearby on fire without blowing a fuse using only an amp or two if you're unlucky) because it's sitting on, say, metal earthed desk, it's now still floating at mains voltage. However, now it won't deliver microamps, it can deliver a lot more though that carbonised previously-a-capacitor-now-a-small-resistor. If you touch it and have a decent connection to ground, instead of the interference with pacemakers, it can become a turbocharged pacemaker, but your heart doesn't work so well at 50/60Hz and may object to this by going on strike. Regulators for some reason think this is a problem, so you use a special safety capacitor called a "Y" or "X" type, depending on exactly how you use it, which is designed to satisfy them that you probably won't discontinue anyone's sinus rhythm or burn down a building (even if they've actually consented by buying your product!)
So, while is this not an intentional effect, it's also an calculated aspect of the power supply design in the absence of an earth wire and is not a sign of a defect or danger. Other than reminding you that the only thing between you and mains voltage is insulation that's carefully specified, regulated and tested to be safe, for some standardised definition of "safe", of course.
You can also see a much stronger version of this effect with a plasma globe (remember them?). The frequency and the voltage is much higher than 50Hz mains, but the principle is the same: the sphere surface is isolated plastic, there's a very small capacitance to the coil. The current flowing in the low pressure gas in the void is what makes the tendrils. With your with your hand on it, you float at very high voltage and can even produce a tiny sub-millimetre, continuous spark to other objects as the small current flows back and forth into this small capacitance. In retrospect, that plasma globe probably has questionable EMI behaviour when doing that!
Interesting! Thanks for the cool info dump. Lack of earthing seemed like the obvious source of problems, but I knew nothing about the details.
Given that one of the devices in question was a Mac Mini (which did indeed have a two-prong plug without earthing), I wonder why Apple didn't put in a little more effort to give consumers an earthed plug. There's more than enough margin on their devices, and computer-like appliances normally have grounded plugs here anyway (Netherlands).
Unearthed two-prong plugs are slightly more convenient here because they fit in more sockets. But I'd prefer earthing over that small convenience.
Given that one of the devices in question was a Mac Mini (which did indeed have a two-prong plug without earthing), I wonder why Apple didn't put in a little more effort to give consumers an earthed plug. There's more than enough margin on their devices, and computer-like appliances normally have grounded plugs here anyway (Netherlands).
Unearthed two-prong plugs are slightly more convenient here because they fit in more sockets. But I'd prefer earthing over that small convenience.
If you can't rely on your customers always having an earthed outlet to hand (as you can't in countries that permit unearthed sockets, or often have dodgy electrics), you have to design it to work without the earth line in case a customer uses that socket.
Adding an earth conductor would require a thicker, less flexible 3-wire cable, a bigger plug (in the countries that have the option of a 2-pronger) and a three-pin power connector if it's not a captive cable, which is bigger and heavier. To ground that Y capacitor node means taking the earth conductor from the socket to near the SMPS transformer, and you have to maintain strict clearance and creepage distances between that conductor and the live/neutral regions at all points. Modern power supplies are very compact, so this is actually more of an ask than you might expect.
As the device is already designed to meet or exceed safety requirements without the earth wire, all it does is avoid the tingle and add weight, volume, design effort and component cost. As mass market devices produced by the hundreds of millions, this is not deemed a good tradeoff.
You can avoid this on your own, however, by grounding the case yourself, by connecting any exposed metal to a local earth point. Remember that Macs are anodised, so the surface isn't really conductive, (which actually amplifies the effect at the point of contact as a thin insulator is also a capacitor!).
Adding an earth conductor would require a thicker, less flexible 3-wire cable, a bigger plug (in the countries that have the option of a 2-pronger) and a three-pin power connector if it's not a captive cable, which is bigger and heavier. To ground that Y capacitor node means taking the earth conductor from the socket to near the SMPS transformer, and you have to maintain strict clearance and creepage distances between that conductor and the live/neutral regions at all points. Modern power supplies are very compact, so this is actually more of an ask than you might expect.
As the device is already designed to meet or exceed safety requirements without the earth wire, all it does is avoid the tingle and add weight, volume, design effort and component cost. As mass market devices produced by the hundreds of millions, this is not deemed a good tradeoff.
You can avoid this on your own, however, by grounding the case yourself, by connecting any exposed metal to a local earth point. Remember that Macs are anodised, so the surface isn't really conductive, (which actually amplifies the effect at the point of contact as a thin insulator is also a capacitor!).
I see! Apple had the option to supply a fat three-prong plug here, which wouldn't fit in any unearthed socket, except for fake ones (which do exist but are generally older extension cords over here). But as you say, they likely didn't think this was worth the trouble + customer inconvenience if they couldn't rely on earthing elsewhere.
At least in the UK, it's infamously only Earthed if you use the long extension cable (instead of plugging 'wall wart' in directly) that they no longer supply.
> Unearthed two-prong plugs are slightly more convenient here because they fit in more sockets.
That argument doesn't work here, all are 3 pin. It's a conducting third pin too, even though it's NC, which isn't even compliant.
My suspicion is that it's way more noticeable on European voltages (frequency could also be a factor?) so they don't notice in the US and don't care. I have a few products that do it; they're all US companies except one Japanese (slightly lower than US even at 100v, and product primarily sold to US I suspect).
My Framework laptop will shut down if it touches a charging but un-Earthed MacBook.
> Unearthed two-prong plugs are slightly more convenient here because they fit in more sockets.
That argument doesn't work here, all are 3 pin. It's a conducting third pin too, even though it's NC, which isn't even compliant.
My suspicion is that it's way more noticeable on European voltages (frequency could also be a factor?) so they don't notice in the US and don't care. I have a few products that do it; they're all US companies except one Japanese (slightly lower than US even at 100v, and product primarily sold to US I suspect).
My Framework laptop will shut down if it touches a charging but un-Earthed MacBook.
I absolutely *loved* reading your comment! It was the right mixture of knowledgeable and humorous, and kept me gripped, not unlike a fine wodehouse novel. :)
Once you can feel it (say 50V) then you can have data problems with anything else plugged in.
So often worth fixing even if you don't worry about getting a shock.
So often worth fixing even if you don't worry about getting a shock.
I don't think it's quite the same thing. Laptops in particular often have machined (?) surfaces that feel very weird to the touch, regardless of electricity. HP in particular is a regular offender, though I haven't touched many apple computers.
I've experienced it and it's markedly different how a laptop feels when plugged into the wall Vs not: it's because of a relatively high voltage (but also high impedance, so not dangerous, though sometimes painful if it focuses through a small point like a USB cable) hum you tend to see in the ground of most modern power adaptors due to noise reduction capacitors.
No, this is a different thing. It's leakage current from ungrounded power supplies (the two-prong apple power brick) and it's extremely noticeable. Couple hundred microamps, feels like licking a 9 volt battery.
Is that explained by capacitance? I'm sure the capacitance of your finger through paint is pretty low but capacitors allow AC to pass
While trying to take photos of last night's aurora my phone touch screen was acting a bit wonky. I wondered if it could somehow be related.
Can you provide an example of an object where this can be felt? I’ve touched hundreds of painted electrical enclosures on energized transformers, panels, switchgear, etc and have never noticed this.
Macbook plugged into a non-grounded charger.
There are many examples of humans being able to observe a difference, yet deny their capability to discern on the basis of abstract rational knowledge.
Another example is frame rates: while its well known that the bandwidth of light sensitive cones on the retina is around 30Hz cycle frequency (and thus ~60Hz framerate), many gamers felt the difference of higher framerates, even though many of the same gamers denied observability of this difference on the basis of knowledge of this basic biological fact.
The biological fact is not wrong: if screen pixel projects are at rest on the retina. But when the eye is rotating to follow a depicted object on the screen, then speeds higher than ~60 pixels per second result in motion blur that would be absent when observing a real life object moving at the same angular speeds. The biological fact is still true, but simply not naively applicable in the context of motion blur due to eyeballs rotating while observing a display.
Another example is frame rates: while its well known that the bandwidth of light sensitive cones on the retina is around 30Hz cycle frequency (and thus ~60Hz framerate), many gamers felt the difference of higher framerates, even though many of the same gamers denied observability of this difference on the basis of knowledge of this basic biological fact.
The biological fact is not wrong: if screen pixel projects are at rest on the retina. But when the eye is rotating to follow a depicted object on the screen, then speeds higher than ~60 pixels per second result in motion blur that would be absent when observing a real life object moving at the same angular speeds. The biological fact is still true, but simply not naively applicable in the context of motion blur due to eyeballs rotating while observing a display.
It's more complicated than that, brain cuts out the blurry "in between" frames when you move your eyes. Which means it has to extrapolate the images from before the movement to fill the gaps. There's many weird effects of this hack - for example when you look at something moving very fast (like wheels of passing vehicles) but don't move your eyes - it looks blurry. But when you move your eyes - the frame in your brain "freezes" and you can notice non-blurry details on the fast moving things. There are even ways to force eyes to see stuff from the past (like seconds' hand on a clock moving at different rates depending if you move your eyes).
You can't actually say that human eye has a strict fps, so the higher screen fps the less weird interactions with the ugly hacks in our brains.
You can't actually say that human eye has a strict fps, so the higher screen fps the less weird interactions with the ugly hacks in our brains.
when your eyes are motion tracking an object there is no cutting-out going on, that only happens when the brain intentionally decides to track a new object
Your eyes being analog and the 60Hz display being offset from your own cycle frequency would play large roles in that.
Eyes don't have a synchronous cycle. Every individual receptor has a relaxation time starting from the last excitation.
the phenomenon I describe is much simpler, and is remediated by having the backlight of a 60 Hz display have a very short single on strobe. If they backlight remains on or flashes multiple times during a single frame then the pixel will draw a long streak on the retina (because the eye was rotating to track a depicted moving object)
Sample and hold motion blur during smooth pursuit is far from the only visual artifact resulting from low frame rates.
What are others?
I'm not sure if you've seen them, but there are LED glow sticks that look normal when stationary but leave sort of a trail of distinct after images rather than a smooth blur when waved. I've seen LED Christmas lights that have a similar effect when you scan your eyes past them quickly. It's called the phantom array effect, and it's caused by a flickering light (LEDs lit with less than 100% duty cycle) moving rapidly across the visual field.
Mitigating sample and hold motion blur by blacking out the display for some of the frame time turns your display into a flickering light source, so it can potentially produce the same effect for small bright objects on dark backgrounds when either the object moves rapidly on screen or you scan your eyes across the screen. It's fairly niche in that it'd only affect some rather specific scenes and even then can depend on how the scene is viewed (it won't occur if you track the only fast-moving bright object with your eyes, and it's much reduced in higher ambient light), but the flicker fusion rate is generally several kilohertz, so you'd need to boost the hell out of the frame rate to guarantee the effect is eliminated altogether.
More generally, an object that is moving rapidly enough for its screen position to change by many pixels per frame can have its motion look jerky even without motion blur. And, in fact, motion blur can help disguise that.
Mitigating sample and hold motion blur by blacking out the display for some of the frame time turns your display into a flickering light source, so it can potentially produce the same effect for small bright objects on dark backgrounds when either the object moves rapidly on screen or you scan your eyes across the screen. It's fairly niche in that it'd only affect some rather specific scenes and even then can depend on how the scene is viewed (it won't occur if you track the only fast-moving bright object with your eyes, and it's much reduced in higher ambient light), but the flicker fusion rate is generally several kilohertz, so you'd need to boost the hell out of the frame rate to guarantee the effect is eliminated altogether.
More generally, an object that is moving rapidly enough for its screen position to change by many pixels per frame can have its motion look jerky even without motion blur. And, in fact, motion blur can help disguise that.
This is a very interesting concept
Is there a way to sync the monitor’s refresh rate to a different phase/offset?
It would be cool to play with that setting and see the effects on our perception of the screen
Is there a way to sync the monitor’s refresh rate to a different phase/offset?
It would be cool to play with that setting and see the effects on our perception of the screen
Not much of an electrician but wouldn’t the phase kind of randomly reset every time you turn the monitor on and off?
Our eyes are good at adapting to all kinds of things - like really small red, green and blue lights in an array can look like anything to us
Our eyes are good at adapting to all kinds of things - like really small red, green and blue lights in an array can look like anything to us
That makes a lot of sense
About turning the screen on and off, it’s very slow if I want to change it in real time. It would be nice to have a little nob on the side and just change the phase one way or the other in correspondingly :)
About turning the screen on and off, it’s very slow if I want to change it in real time. It would be nice to have a little nob on the side and just change the phase one way or the other in correspondingly :)
I think you're the one denying rational knowledge here. People are different, and there are in fact people who cannot tell the difference between higher frame rates, as shown in studies.
Just because you can see it doesn't mean others can.
Just because you can see it doesn't mean others can.
the problem is not rational knowledge, its misapplying rational knowledge in circumstances where it does not apply.
its extremely easy to reproduce, and I have not encountered anyone who fails to see it once told how to reproduce it:
suppose your screen is 1920 pixels wide (Full HD). suppose a patter contains high spatial bandwidths, i.e. high spatial resolutions like text.
obviously if a monitor is able to display say at a 60 Hz frame rate, then motion blur would be essentially absent if the font bitmap is moved 1 pixel per frame, or at least the motion blur would be constrained to 1 pixel of horizontal blur.
to traverse about 1920 pixels from the left side of the screen to the right at 1 pixel per frame (or 60 pixels per second) would take 32 SECONDS. Half a minute!
consider much faster velocities, say 3 seconds for a word to move from the left side of your screen to the right, thats motion blur such that a pixel is blurred the length of 10 pixels! Most people would not consider this very fast at all.
now take note of the DPI of the screen and print the same text at the same dimensions on paper, and hold it up close to your screen, and move it from left to right in about 3 seconds, while following it with your eye. You wont see motion blur on the real piece of paper, but you will on the digitally rendered text of same dimensions and velocity...
once you understand this phenomenon, you will understand in what sense the flicker bandwidth of human retina at rest with respect to a visual stimulus should not be confused for a sufficient framerate to accurately reproduce the perception of visual stimuli representing motion, unless the backlight is strobed at a very low duty cycle. but then flicker becomes visible again unless we bump the framerate up a notch again.
its extremely easy to reproduce, and I have not encountered anyone who fails to see it once told how to reproduce it:
suppose your screen is 1920 pixels wide (Full HD). suppose a patter contains high spatial bandwidths, i.e. high spatial resolutions like text.
obviously if a monitor is able to display say at a 60 Hz frame rate, then motion blur would be essentially absent if the font bitmap is moved 1 pixel per frame, or at least the motion blur would be constrained to 1 pixel of horizontal blur.
to traverse about 1920 pixels from the left side of the screen to the right at 1 pixel per frame (or 60 pixels per second) would take 32 SECONDS. Half a minute!
consider much faster velocities, say 3 seconds for a word to move from the left side of your screen to the right, thats motion blur such that a pixel is blurred the length of 10 pixels! Most people would not consider this very fast at all.
now take note of the DPI of the screen and print the same text at the same dimensions on paper, and hold it up close to your screen, and move it from left to right in about 3 seconds, while following it with your eye. You wont see motion blur on the real piece of paper, but you will on the digitally rendered text of same dimensions and velocity...
once you understand this phenomenon, you will understand in what sense the flicker bandwidth of human retina at rest with respect to a visual stimulus should not be confused for a sufficient framerate to accurately reproduce the perception of visual stimuli representing motion, unless the backlight is strobed at a very low duty cycle. but then flicker becomes visible again unless we bump the framerate up a notch again.
I’d say lots of behavioural cues, for instance related to dominance. Many people feel like they’re behaving freely because they’ve completely internalized the constraints their social position imposes upon them.
The McGurk effect https://www.youtube.com/watch?v=2k8fHR9jKVM is another example, which might be described as people learning to lip read without them being aware that they have done so.
Apparently I can't lip read, as I never heard anything other than "baa" even as the video was claiming that I should be hearing something different.
Yeah, I don't understand what I was supposed to be seeing or hearing in that clip, and they never bothered to explain it.
The guy says "Baa" and we see his lips move accordingly. Then we hear him say "Baa" again, but this time he's obviously pronouncing something else, judging by his lip movements. We don't know what he's saying (or at least those of us without lip-reading skills don't), but nothing unusual or tricky seems to be happening.
What am I missing?
The guy says "Baa" and we see his lips move accordingly. Then we hear him say "Baa" again, but this time he's obviously pronouncing something else, judging by his lip movements. We don't know what he's saying (or at least those of us without lip-reading skills don't), but nothing unusual or tricky seems to be happening.
What am I missing?
From making the same motions with my mouth I was able to figure out that the other thing he's saying is "faa", so I'm guessing some people literally hear "faa" even though the audio is "baa"?
> how many other things there are that people subconsciously learns, without it ever becoming obviously noticeable for them?
95%+? Stuff like how to jiggle keys on a keyring to get the right one for the door you're about to unlock? This only works for your keyring, it's highly kinetic, tactile, initial condition dependent etc, yet yet can usually be done unconsciously IME with the 6 keys on my keyring.
95%+? Stuff like how to jiggle keys on a keyring to get the right one for the door you're about to unlock? This only works for your keyring, it's highly kinetic, tactile, initial condition dependent etc, yet yet can usually be done unconsciously IME with the 6 keys on my keyring.
I _think_ I can tell whether a car is an ICE / hybrid / electric just by the way their weight shifts around corners. My friends maintain they cannot, but under test conditions,
I'm sure they'd be fine.
Are you sure it's weight distribution and not conducted engine vibration and gear shift patterns? Seems like it'd be difficult to control for (assuming we're already controlling for engine noise).
I'm pretty sure it's weight distribution. Like I can tell the difference between a hybrid Camry and a pure ICE Camry based on how it bobs over speed bumps, not just in cornering / acceleration.
I remember the first time I noticed that I could guess correctly which fingertip a friend shining a tiny red pen laser was shining it on, just from minuscule temperature differences.
That you can feel artificial lighting as heat (the actual light, demonstrated as it was a laser some distance away) at such a low power level (<5mW) was pretty surprising to me.
That you can feel artificial lighting as heat (the actual light, demonstrated as it was a laser some distance away) at such a low power level (<5mW) was pretty surprising to me.
Reminds me of Feynman's trick of guessing which book on a bookshelf a person had handled based on the smell.
Poor storytelling in modern cinema.
There is a cool veritasium video in which they show we are sensitive to changes in the magnetic field surrounding us
We can’t consciously tell, but they can see our brain lighting up when sensing the changes
Link to video: https://youtu.be/dg3pza4y2ws?si=-yXtwIu2n4QR_1Wi
We can’t consciously tell, but they can see our brain lighting up when sensing the changes
Link to video: https://youtu.be/dg3pza4y2ws?si=-yXtwIu2n4QR_1Wi
I noticed if I stare into the forest without focusing on any particular thing my vision starts to shimmer a bit and sometimes there are distinctive little perturbations in my peripheral vision.
My mind wants to immediately look directly at the perturbations at an almost instinctive level. If I do look I frequently see a leaf moving in the wind or a bird or squirrel moving around in the tree.
By intentionally using this effect rather than actively scanning the forest I find I am much better at finding birds when bird watching or seeing larger animals such as foxes, deer, or snakes moving in the grass.
It's amazing how many things our bodies are capable of that we don't know about until we step away from electronics and machinery and just let the body do its thing.
My mind wants to immediately look directly at the perturbations at an almost instinctive level. If I do look I frequently see a leaf moving in the wind or a bird or squirrel moving around in the tree.
By intentionally using this effect rather than actively scanning the forest I find I am much better at finding birds when bird watching or seeing larger animals such as foxes, deer, or snakes moving in the grass.
It's amazing how many things our bodies are capable of that we don't know about until we step away from electronics and machinery and just let the body do its thing.
The woman who can smell Parkinson's comes to mind as a recent example.
Many people can perceive polarized light.
Most of your knowledge is implicit.
When running some water to warm up before turning on the shower head, I can tell when the hot water has arrived by the distinct change in the sound as it splashes on the shower basin. The splash sounds soften when the water starts to run hot.
This is the same context where I noticed this. One of those weird things that would be really easy to google but I never did. Wasn't expected to get that random mystery solved today but I'll take it!
Archived: https://archive.ph/ITRzw
And the audio clip (which doesn't work on the archive): https://static.nytimes.com/podcasts/2024/05/09/science/09tb-...
Someone appears to have made an android app to attempt to distinguish temperature from sound of pour -
https://petter.saterskog.com/ai-thermometer/index.htm
I thought I'd heard the 'stickiness' of the water affects how it sounds. Not sure if that is stiction or something else.
I thought I'd heard the 'stickiness' of the water affects how it sounds. Not sure if that is stiction or something else.
I thought I wouldn't be able to tell the difference, but when he told me to pause the video to try to guess, I listened to the audio of pouring water again, and thought about "which one sounds like when I pour tea", and that way I could identify the warm/cold water. Interesting!
I noticed the sound when making hot chocolate for my child. I figured there are a number of things at play... the leidenfrost effect when the water hits the much hotter edge above the waterline in a kettle(not in this video), the air over the hot water being more humid (and thus lighter), the much higher vapor pressure, the difference in surface tension, the dissolving of the hot chocolate powder, etc.
Viscosity isn't something I considered... but it makes sense.
Viscosity isn't something I considered... but it makes sense.
I can definitely hear when the shower gets hot. Cool to have some explanation behind it.
Likewise. My shower takes quite a long time to run hot, and I can usually hear when it has reached the point where it is no longer too uncomfortable to get in.
Yeah, my shower takes a a while to run hot, so I also listen for when the water is ready.
It took a while to find the original source files [i.e. the ones the author published as supplementary information]
Includes raw recordings as well as actual raw results for those of us without NYT subscriptions.
https://osf.io/brp2a/?view_only=7f49783ebbf646b29af32ca64524...
Audio comparison video, the fun part for me anyway.
https://osf.io/brp2a/files/osfstorage/62fe7d9da06acd0f5b2db3...
Includes raw recordings as well as actual raw results for those of us without NYT subscriptions.
https://osf.io/brp2a/?view_only=7f49783ebbf646b29af32ca64524...
Audio comparison video, the fun part for me anyway.
https://osf.io/brp2a/files/osfstorage/62fe7d9da06acd0f5b2db3...
Absolutely, yes. Pouring hot water into a cup sounds very different from pouring cold water into a cup. Even the flow looks visibly different, hot water is a lot more "lively". Noticed this as a kid, never made a mistake.
also the sound the cup makes when you hit it with a spoon while stirring
From personal experience, walking on snow/ice sounds different based on temperature. From my time of walking to work at 6am in Michigan when I was younger, I could tell the temperature in approximately 10 degree F increments based on the sound. At least between 30F to -10F
This is a well-known phenomenon in Nordic countries I believe. There is a verb "narskua" in Finnish which is only used to describe the sound of walking on snow in below freezing temperatures.
Google AI tells me:
"The Finnish word narskua translates to "crunch" or "scrunch" in English. It's an onomatopoetic verb that describes the sound snow makes when you step on it in very cold temperatures"
Google AI tells me:
"The Finnish word narskua translates to "crunch" or "scrunch" in English. It's an onomatopoetic verb that describes the sound snow makes when you step on it in very cold temperatures"
There's definitely many, many different sounds of snow and ice based on temperature, and probably humidity, pressure, etc. Or what those conditions were 2 days ago when the snow fell, what they were yesterday, and what they are now. I live in Canada, Québec so maybe that makes me some kind of subjective authority.
As someone from Arizona I learned relatively late in life that ~15F is when my nose hairs start to freeze.
Link to the preprint: https://arxiv.org/abs/2403.14740
Can anyone explain why hot water tastes different to cold water? Is taste not separable from temperature or is there another mechanism at work?
Taste is absolutely linked with temperature. Cold vs hot coffee for example. Don’t know exactly why. Most things tend to taste “more” when hot. Could be the intensity of molecular activity, which is what temperature is, that varies and so registers more or less strongly with our taste preceptors
This can be more readily observed with food IMO. Hot pizza tastes way better than cold pizza (though, of course, cold pizza still tastes great)
I'd guess much of this difference is also due to the fats in the cheese & meats solidifying at cold temperatures, and thus less readily coating taste receptors.
Or why kids tend to let their ice cream melt into “soup”, it tastes sweeter when warm
A lot of things at play.
1) We actually can sense "coldness" or "hotness" as separate tastes. Think about mint candies or pepper for example.
2) Our receptors have different sensitivity based on the temperature. For example cold sweet drink feels much less sweet. That's why warm cola is disgustingly sweet for example.
And water does contain a lot of dissolved salts which have a taste.
3) More than half of the taste we feel is actually coming from the smell, and warm water contains more vapour, and therefore, more smell.
So our brain takes all these inputs from different sources and synthesises the feeling of taste in our brain.
Source of this knowledge is from: https://www.cookingforgeeks.com
1) We actually can sense "coldness" or "hotness" as separate tastes. Think about mint candies or pepper for example.
2) Our receptors have different sensitivity based on the temperature. For example cold sweet drink feels much less sweet. That's why warm cola is disgustingly sweet for example.
And water does contain a lot of dissolved salts which have a taste.
3) More than half of the taste we feel is actually coming from the smell, and warm water contains more vapour, and therefore, more smell.
So our brain takes all these inputs from different sources and synthesises the feeling of taste in our brain.
Source of this knowledge is from: https://www.cookingforgeeks.com
I would imagine it has with the biomechanics of our tongue as it relates to available dissolved minerals.
Just look at the inside of any water heater. Usually disgusting! This is why we heat cold water up when we cook, rather than start with hot water
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I read about the viscosity difference in hot/cold water a while back. Every time I think about it while drinking water, I put my water down. I don't know why it bothers me so much but it does. I feel like I peered into the eyes of God and can never return to normal life.
Humans can sense quite a few strange things. Like the smell of rain up to 100 parts per trillion.
I was taught to listen to the sound the water made in the sink to tell when the hot was ready. I had always assumed this was something most folks already knew about.
Do you know how to download sound from nytimes.com? I can show the article on the website (not on archive one) and I would like to analyze the sound in audio software.
If you wade through the (incredibly verbose) HTML you can eventually find a script with the source for the audio file, which is:
https://static.nytimes.com/podcasts/2024/05/09/science/09tb-...
https://static.nytimes.com/podcasts/2024/05/09/science/09tb-...
It's easy enough to reproduce - may as well run a quick experiment and record that.
You some controls: for example, the same mass/second of water - your water pressure might differ between hot and cold sources.
Let us know the results please
Second sample has significant hi-hat style sustain, since I know it is hot water it should be a steam. First sample has really little amount of this sound which might be produced from bubbles. First sample is really interesting because it has 2 bass lines: first starts at 900Hz and rising to 100Hz, second starts at 600Hz and quickly dropping to 400Hz and keep lowering slowly to 300Hz. Definitely not harmonicas, it is something like 2 independent resonating frequencies for something inside of glass-and-water sound source. Bassline of second sound is singular fat line; firstly it starts at 700Hz and slowly grows upto 1kHz.
Probably the 2 basslines from the first samples (cold) was something that bothered the dog, maybe the thing is in rich sound such as chord vs single note. I don't care about bubbles but when I will have an access to a nice microphone I will try to record more samples of this. The hard part is how to remove water from the glass between 2 or more experiments because it is important to have really similar setups without moving the glass even slightly.
Probably the 2 basslines from the first samples (cold) was something that bothered the dog, maybe the thing is in rich sound such as chord vs single note. I don't care about bubbles but when I will have an access to a nice microphone I will try to record more samples of this. The hard part is how to remove water from the glass between 2 or more experiments because it is important to have really similar setups without moving the glass even slightly.
Also hard vs soft water may sound different, not just carbonated water. Soft water feels smoother and silkier on the skin because it contains less minerals.
I always thought I could do this but hadn't admitted it to anyone because of its preposterousness. Huh.
Yes, for sure, but at what resolution?
The article doesn’t even give the reason lmfao journalism is so dead
Huh, I guess this is why movies never have convincingly cold water. Everyone is shivering, but it never sounds cold.
Googling, it sounds like cold showers are fairly common in movies https://www.reddit.com/r/explainlikeimfive/comments/dg52a5/e...
That kind of sound effect is usually added in post anyway.
Right, my point is that everything about a scene should sound cold. Foley work can get you some of the way, but the ambient temperature is probably less like a prop and more like white balance. Since no one is approaching it that way, it never sounds right. If you didn't grow up in the cold you probably never noticed, but few movies ever properly convey it.