Helium (some extra stuff) - Periodic Table of Videos

More about Helium. The main video is at • Helium - Periodic Tabl...
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Featuring Sir Martyn Poliakoff and Neil Barnes.
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[@Povland]

Neils face kills me. He looks so serious, but when Martyn starts to speak Neil face lightens up

[@TheodoreTsatsaronis999]

Povland oh man you are absolutely right😂😂😂😂

[@ZaphodHarkonnen]

Neil's reaction is what makes that whole thing amazing.

[@chabis]

Even a stone couldn't watch this video without smiling, I'd say ;-)

[@Tuning3434]

+Povland I'm suspecting Neil is deliberately trying to become a meme.

[@Povland]

Neil is the best meme

[@Wezleigh]

“I sure hope I don’t die from breathing helium, but that would be an interesting video”

[@pseudomonad]

That's commitment!

[@daedra40]

Gotta love the professor.

[@therugburnz]

Wezleigh Sir Martyn uses that classic British humor to its classic subtlety.

[@ATH_Berkshire]

Wezleigh i

[@Biped]

Neil's face approves

[@LateNightHacks]

Neil's reaction is even more funny

[@chabis]

LateNightHacks He has a very special (probably very British) way of enjoying himself. But he definitely does.

[@avi1923]

6:42 Neil's smile made my day!! Great video!! 👌👌👌

[@gaminawulfsdottir3253]

Neil always cracks me up.

[@stefanklass6763]

The sound of the Phone doesn’t pitch up because the speakers work completely different from the vocal chords. Our voice is an instrument that works with airflow, like a pipe or a trumpet or a saxophone, so the sound-creating device resonates with the air in a certain compartment whereas the speaker has a membrane that is driven by an electric coil. The frequency is forced upon it by the electric signal and can‘t be changed. It is quieter because the membrane can‘t transmit enough energy to the lighter gas as it would to air. If you want to design speakers for a helium atmosphere, you have to give them a greater amplitude or a larger surface area. I postulate that a pipe would pitch up when you play it with helium, but a guitar wouldn’t. It would just be more quiet like the speaker.

[@fearofchicke]

Stefan Klass wouldn’t comparing a speaker to a drum be a better analogy?

[@KalebMarshallDulcimerPlayer]

Have you ever checked what helium does to the pitch range of your voice? I've checked my own, with an electronic tuner, and helium doesn't seem to change anything. I hypothesize that helium acts like an EQ and adjusts the overtones and undertones.

[@stefanklass6763]

fearofchicken It might depends on the sort of drum. I‘m not sure if some drums are dependent of the resonating air inside (or how much influence it has)

[@Braedley]

I agree with the first part, but I have to think through the second part. I was thinking about a wave theory explanation and the interface between the helium and air causing total internal reflection, but that would imply the index of refraction for helium is higher than the index of refraction for air, but that doesn't jive with the observed speeds of sound (speed of sound in helium is apparently about 3x as much as air). Is energy carried in a sound wave proportional to the density of the material? If that's the case (which "feels" right to me), then the speaker producing the same amplitude (or modestly higher amplitude) waves would mean those waves carry less energy.

[@leosedf]

Great, now let's build insulating foam with helium, will attenuate sound even more.

[@thorwaldjohanson2526]

As a diver myself I have to correct the explanation with the helium and deep sea diving. While it is true that nitrogen goes into your blood and it is a problem, the main reason for divers breathing helium is that nitrogen and oxigen become toxic at higher pressures. Nitrogen poisoning can occur at 40+m and it's a bit like being drunk, oxygen poisoning occurs at depth of 50-60m, which causes your muscles to cramp, including your breathing muscles. So it is impossible to dive deeper with normal air. Since Helium is a nobel gas, it's not toxic at all and you can just mix more and more helium into your mixture, the deeper you go in order to keep the partial pressures of nitrogen and oxygen below their toxic limits

[@z987k]

And to expand on this, helium comes out of solution much easier than nitrogen and actually makes the bends a bigger problem when diving on tri-mix.

[@user-sx4yu3nw4j]

Bingo; oxygen toxicity is a killer. I’m a little disappointed they weren’t able to include a clip of the ‘helium descrambler’ device he was describing, being used by heliox or trimix divers 🤷🏻‍♂️

[@z987k]

@Tt Miller it's toxic at certain concentrations. You reduce the partial pressure of o2 down to just above hypoxic levels.

[@user-sx4yu3nw4j]

Tt Miller of course, nobody is suggesting ALL the O2 be removed, it just needs to be *very* carefully controlled to avoid the lethal threat of toxicity. Normally, on the surface, the air we breathe has a LOT more O2 in each breath than we could possibly metabolize. But it’s ndb because it’s not at high pressure. Only when you breathe O2 under high pressure AND at sea-level concentrations is toxicity an issue. There’s nothing that can be done to address the high pressure issue at depth, that’s just part of diving. But the concentration of O2 can be controlled... and that’s where heliox and tri-mix comes in.

[@motobrikerestorations1354]

@@user-sx4yu3nw4j Not a diver but a dive boat chief engineer. I remember standing with the LST's listening to the divers it sat explaining an issue. I never had an idea what they where saying but the LST's happily interpreted. Not sure about 'descamblers' except for through water comms

[@detritus10001]

I love the professor. This channel makes me wish I had gone to university. It took me until the age of 25 to realize I wanted to be a chemist. Thank you to the team, and Brady for making these video possible.

[@lennyface2586]

2 comments

[@electronicsNmore]

Looking at you with that voice.......hilarious. Called the "Bends", because you feel the pain in your joints, especially when you move them. I dove with a buddy in the past that got the Bends.

[@taofledermaus]

CONGRATULATIONS on 1 million subs!!

[@ArtyomPlatonev]

how are you everywhere that i watch?

[@theburningtoastmonsterofur7028]

Congrats

[@danparden8103]

my other favorite channel

[@nelsonalmeida8827]

The professor says, at about 2:55, that helium is used by divers to avoid "the bends". That is not correct (as briefly noted by the text on screen). The reason that helium is used by divers is to minimize the narcotic effect of nitrogen, which can be severely debilitating. That is why sports divers commonly use trimix (a mixture of oxygen, nitrogen and helium) for dives below 40m. Commercial divers, on the other hand, tend to use heliox (just oxygen and helium) for deep dives. In any case, whatever the gas mix being used, there is a need to control the ascent speed and, quite often, do decompression stops, to avoid decompression sickness ("the bends"). In fact, there is no reduction in decompression time from using helium in the breathing gas.

[@user-sx4yu3nw4j]

Nelson Almeida nitrogen narcosis, yes, but at extreme depths oxygen toxicity is lethal

[@user-sx4yu3nw4j]

Nelson Almeida this is what happens when a chemist tries to answer a physiology question

[@Ktulu789]

So Neil CAN laugh! What an amazing discovery! I bet that he goes HeHeHe!

[@fdavillar]

In diving: Adding to the BENDS problem caused by the Nitrogen, the OXYGEN become toxic in specific high partial pressures. As an example the normal air (21% O2) have "toxic O2 pp" from 64m deep (7.4 Bar) and beyond.

[@lohphat]

The risk with breathing He is hypoxia -- displacement and thus insufficient absorption of O2. You will pass out and you may experience respiratory arrest. You will not feel as though you're suffocating because there's no build-up of CO2 which triggers the gasping/suffocation response, so you continue -- then you may experience euphoria thinking it's enjoyable...until you lose consciousness. So don't do this alone -- just like diving or hiking or boating. Have someone who can help you.

[@lohphat]

Ejuice Vaper No need, l lost a loved one this way.

[@kasnitch]

lol Neil . is he a guard at the palace on days off ?

[@RWBHere]

Argh! His cover is blown!

[@tayet6875]

I really enjoyed this addition to the Helium chapter!

[@luppa79]

6:45 What a wonderful world playing, bag floats down and the guys appear from behind... what movie magic!

[@nathanz4441]

I'm collecting as many elements as I can because of your videos. I hope you received one million subscribers.

[@denispol79]

Niel's face, when he's fighting the smile... priceless!

[@bpark10001]

It is helium 4 that becomes a superfluid at 2 degrees K, not helium3. Helium 4 cannot be used as a refrigerant below 2K because of this, so the rare helium 3 must be used for refrigeration of very low temperature experiments. (Magnetic effects can also be used to achieve these low temperatures.)

[@christopherleubner6633]

The helium recondensor on a MRI uses a mix of helium 3 and 4 to make a mixture that won't liquefy at the condensation point of helium 4. The gas fill is extremely expensive for these cryogenic cooling devices.😮

[@tidytibsgmail]

The reason the sound is getting quieter starting at 5:30 to 5:35 is the Helium in the bag (0.178 kg/m3 or 0.011 lbs/ft3) is almost 7 times less dense than air (1.229 kg/m3 or 0.076 lbs/ft3). Sound would have to work harder to transmit energy from one point to another to produce sound at the same volume. This is the same effect when you are vacuuming out air of a chamber with a speaker playing music. I hope that clarifies things.

[@koharaisevo3666]

It quieter perhaps because Helium molecules hit the bag with less kinetic energy due to its smaller mass than air molecules.

[@ianto3453]

Koha Raisevo But they move faster too

[@koharaisevo3666]

Only sound (pressure wave) propagate faster, Helium molecules do not move faster

[@KairuHakubi]

I would imagine it's because of the barrier. The sound has to change speed AND smack into some plastic. It can do one or the other more easily

[@ianto3453]

Koha Raisevo I meant the mass of the molecules results in faster movement and therefore the same kinetic energy as any other gas at the same temperature

[@DanGrossberg]

Kinetic energy is the same, but momentum is less. Less momentum, therefore less kinetic energy, is transferred to the bag.

[@hashidatackey8758]

HeHe

[@brennonstevens467]

HeHeHeHe

[@theatheistpaladin]

Impossible. Noble gas. Good day, sir!

[@shamsulalam4113]

What do you mean by hehe

[@sjaroszczyk]

haha he does'n get hehe

[@proximacentauri8038]

TheAtheistPaladin lol

[@bnnttdenn]

Neil's silence and his facial expressions makes him special ...

[@ted467]

6:43 new profile picture.

[@altebander2767]

It makes sense for the speaker to become more silent in "not air". The Helium surroundings probably have a different impedance than an environment of air. This creates an impedance missmatch and part of the wave will travel back to the speaker instead of being radiated. Or in layman's terms. The speaker is essentially a membrane pushing against the air. Now the energy it can transfer depends on the amount the air is shifted and the force the membrane has to put up with. The energy is essentially the product of this. Now if the "air" around it is easier or harder to shift, the membrane will either move the same amount as before, or move less. In both cases the amount of transmitted energy is lower. Imagine riding a bikecycle, if you shift in a gear where it's to hard to pedal you won't get far. The same goes for a gear where it's really easy to pedal. Unless you have the right gear (impedance) you won't get optimal energy transfer. Obviously the pitch cannot change as that's determined by the rhythm the speaker membrane moves. BTW in case you ever wondered what that large horn is for on a gramophone player. It's purpose is to gradually change the impedance. That way you can transmit more of the energy. Another place you can hear a sudden change is when standing in front of a large wall at some distance. Any noise you make towards the wall will be reflected back to you after some delay. In German this is called an "Echo" and a popular past time among children. At the wall the acoustic impedance changes abruptly so you get a reflection. If you are in a tunnel you can sometimes hear the opposite, you shout something towards the exit, and the opening will reflect part of it.

[@antiHUMANDesigns]

The vocal cords rely on the movement of air to vibrate, so if the air is different, the vibrations will be different. However, a speaker relies on electromagnetism, so ti doesn't matter if the air changes. Helium is light than air, so it provides less resistance for the vocal cords, so they can vibrate faster using the same tension. But a speaker will vibrate at the same speed even in vacuum or underwater. Could someone please try playing a guitar in helium? :D It should make the notes slightly higher, but it's still the weight of the string that mostly affects how fast it vibrates, not so much the air resistance - I think.

[@johnries5593]

Since I'm under the impression that vocal chords vibrate in almost exactly the same way strings do, I would think that playing a guitar (or any other stringed instrument) in a heliox atmosphere would have almost exactly the same effect as speaking in one.

[@antiHUMANDesigns]

I think that the much heaver weight of the steel strings will mean that their tension plays a larger role than the air that they displace. And since vocal cords have a larger surface, they should depend mroe on the air, whicle a guitar string is very thin and cuts through the air. A guitar string doesn't produce much sound at all, it is the fact that the vibrations carry into the body that makes it loud.

[@antiHUMANDesigns]

Yes, wind instruments would be affected at least as much as vocal cords, perhaps even more.

[@mechadense]

The attenuation in volume is due to the impedance mismatch at the inter medium boundary layer. The usual demo-experiment is a chain of many coupled pendulums that features a sudden step in length.

[@matthiasstammler4641]

mechadense Looking for that exact answer to like.

[@Cinimod105]

Does that mean that if you put your head into the helium-filled plastic bag, it would sound normal without being muffled?

[@user-sx4yu3nw4j]

This is what happens when a chemist tries to answer a physics question.

[@TheArrogantMonk]

Something about those two scientists together brings me such joy

[@ramiusz7336]

Neil cracks me up even more in this one. Glad you got his reaction.

[@rezonite]

Why do I feel so calm listening to you talk?

[@andrewbritton6973]

It's great to see that this channel is almost at 1 million subscribers!

[@Emerson1]

The phone becomes quieter because a) the speaker draws less energy in helium than air.. it is almost like its playing in a weak vacuum (the lower density of helium absorbs less energy from the speaker than does air.. water for example would absorb even more.. so if the current draw of that speaker were measured,say with a miliampmeter, it would be less in helium, more in air, and even more in say water) and b) the acoustic impedance mismatch between the helium and the air causes some of the waves to reflect back at the bag interface (this would apply even if the bag were not there , at least for a moment until the helium would escape). - great video!

[@CONNELL19511216]

It's called 'the bends' because the physical action of N2 bubbles on the muscular and nervous system causes painful spasms including arching of the back

[@muonneutrino2909]

The original name for decompression sickness (DCS) was "caisson disease". This term was introduced in the 19th century, when caissons under pressure were used to keep water from flooding large engineering excavations below the water table, such as bridge supports and tunnels. When the workers returned to the surface after a long shift in the caisson, sometimes the pain in their joints caused by the nitrogen bubbles in their blood would cause them to bend their arms and legs to reduce the pain.

[@Bondubras]

I think the phone becoming quieter is a factor of air density. While it is true that the lighter helium molecules transmit sound faster, Helium also has a much lower molecular density as well, i.e. there's more space between the molecules. The human voice is partially created by what amounts to a resonance chamber that changes the notes of sound coming off of the vocal chords, so since Helium makes the initial sound run at a higher pitch, it makes sense that the final product would be higher as well. This is just compounded by the lower molecular density. The phone, however, is too small have that type of resonator built in so any sounds heard are caused almost entirely by frequency modulation through a speaker that pushes against the air in very specific patterns. So if there's less air to push against, it means that there's less of the frequencies being transmitted. A real interesting halfway point would be a subwoofer or bass speaker. Those work on the same frequency modulation principles as a standard speaker like the phone, but have resonators like the human voice. I'd imagine that a subwoofer in a helium atmosphere would sound quieter, AND have a higher frequency, if only out of the resonator channels.

[@SuperRockyMountainSRM]

Love this professor. You make wrinkles in my brain. Thank you for sharing knowledge to the world.

[@jacobosaavedra7743]

and when the helium filled bag came down from the roof, louis, said, "what a wonderful world". yes, in deed it is.

[@jasoniswrongabouteverythin8230]

10/10 video. Top tier KZbin content. Best thing that's happened all year.

[@shashankd95]

CONGRATULATIONS ON ONE MILLION SUBSCRIBERS Periodic Videos !

[@splitty2530]

Hey periodic videos, thank you for all of your great content. I enjoy it immensely. I love watching your videos on individual elements and seeing applications of them I've only read in books. I do have one gripe, a small one mind you. If you refer to a paper or study, I would like to know who wrote the paper or conducted the study. By mentioning them, you can do all of science a favour by getting people interested in the work and study of people they haven't heard of yet. Thank you again for all your hard work

[@MindCrime550]

In the semiconductor industry, helium is relatively "popular." The fabs are already insanely clean but within the actual equipment certain processes are so sensitive to things like oxygen it has to be absolutely purged clear of oxygen to like 1 part per billion. Since helium is very small but also easily detectable it is used to leak check very critical atmospheres and vacuum chambers. We use turbo pumps, left for hours to pump down to mTorr^-6+ values on each chamber of our machines and then charge them with helium. then we used a very sensitive helium "sniffer" to detect leaks and if you have a "big leak (loose fitting)" you can detect it from 20 feet away. So anyways, helium helps make the cpus/gpus/ram/phones/etc that you're watching this on.

[@davidquirk8097]

I seem to remember from a Horizon programme about saturation diving from the late 70's or early 80's that the main reason for using Helium / Oxygen mix wasn't the bends but Nitrogen Narcosis (referred to as 'rapture of the deep' caused by the pressure of the oxygen/nitrogen mix. This has the effect of impairing the diver's judgement during the dive. The bends only takes effect during surfacing. You still need to decompress when diving on Helium/Oxygen mixes because the problem of dissolved gasses in the blood stream is still there.

[@sjiht0019]

1 million subscribers! congratulations!

[@shashankd95]

HAPPY BIRTHDAY PROFESSOR!! Thank you for making these amazing videos on Chemistry - Written on Dec 16th

[@jonnypowell1998]

Divers use He for two reasons. It isn't narcotic like nitrogen and when added to the breathing mixture it reduces the partial pressure of oxygen which allows for deeper dives since O2 is toxic at high pressures.

[@dw1444]

correct

[@gasdive]

Well you can have N2 based mixtures that are hypoxic. There was quite a bit of Hypoxic N2 saturation diving done in the 60's and early 70's. So hypoxic mixtures isn't actually a reason to use He. Its done for the narcosis, the reduced work of breathing, reduced heat capacity which keeps the divers warmer and the reduced decompression times after long exposures.

[@444stick]

Give this man an hour long video. He keeps saying interesting things then cutting short because of the time constraint.

[@JamesKaramath]

Quite late now, but only recently discovered these great vids from Nottingham! It's helium-4 that goes superfluid at 2.2 K, not helium-3 - (although it does too at 1 mK dependent on the magnetic environment due to its unpaired nucleon). I'm surprised at the lack of note change for the speaker too (maybe because its a standing wave problem sound generated by our vocal cords (frequency is density dependent) and not for a speaker (pure mechanical oscillation created travelling wave)?) , but the attenuation isn't surprising. It's probably the same principal as why acoustic coupling gel is needed to be smeared on a women's stomach for a pre-natal scan. Sound (as with all waves) will partially reflect when there is a change in medium, the greater the difference in medium density (strictly acoustic impedance), the greater the reflection. The density difference is much greater here going between different media so I'm gonna blame that.

[@chrisshaw7328]

The man just has a knack for teaching, I'm fairly sure there's something to having an almost unhealthy obsession for a subject... and speak slowly enough to convey it clearly without overwhelming any of your audience. Previous experience even leads me to suspect that a touch of eccentricity plays a significant role in the same vein as an electrolyte or a catalyst in a chemical reaction, there's a formula in there I'm sure of it but as yet it's just a hypothesis lol.

[@Nighthawke70]

Easy explaination for the bag experiment. Remember that in a given space there are far fewer helium molecules than normal air. In a nutshell, the sound waves did not transmit through helium as well as though air. In some nuclear device tests there have been fizzles due to helium poisoning the reaction, halving or even 2/3 of the theoretical yield.

[@NikeaTiber]

A friend of mine is a physics professor. One day he was thinking about how helium makes your voice a higher pitch, and wondered if argon would make your voice a lower pitch. So he tried it, and as it turns out his conjecture was correct, it does. He started feeling *very* short of breath, and realized that due to the density of the argon he wasn't breathing it all out. So he got up against the wall and did a handstand to get some assistance from gravity and let the argon drain out of his lungs. Even though both can be dangerous, at least helium will leave your lungs with no extra effort. As a welder, I have plenty of bottled argon at my disposal, but I'm terrible at doing handstands, so I've had no desire to see what my voice sounds like after breathing argon. Just thought it was an interesting tangent.

[@kixxknuckles1st732]

Thanks for you hard work everyone at periodic videos

[@fernandoschuindt1665]

The KZbin channel TechIngredients has some amazing videos displaying the sound blocking properties of Helium, and even goes into describing the principle. Worth it.

[@SouthwesternEagle]

Now THIS was a GOOD one!! You answered every question I had!

[@mj2068]

indeed, what a wonderful world, and even more importantly, what a bunch of wonderful people in these videos. thank you all.

[@RandomMan-nv2qh]

Congratssss reaching 1 million subscribers !! ! !

[@mechadense]

Search youtube for saturation diving/divers! There are some interesting videos of such divers in their hyperbaric chamber. Beside their helium voices (which is quite a bit worse than at 1atm surface level and thus makes normal communication via speaking pretty much impossible) they need to deal with isolation, health issues, food issues (e.g. no soda), difficult hygiene, cuttoff of professional medical care and both physical and mental stress. These operations are super expensive, hard work and high responsibility). The hyperbaric chamber is in many repects like a "spaceship". The "divers" cannot leave it even in emergency situations. The chamber is permanently located on the ship above the water surface. Only the coupled diving bell (that is even less spacious) goes down to working depth. From the bell the divers venture out in their diving suits which are again less spacious "spaceships for the divers heads". If the warm water temperature regulation system for the wet body suit does malefunction you die very quickly. So happened.

[@theshadowknows6969]

I love this channel so much.

[@Roy_Godiksen]

5:40 That is Very fascinating. I would expect helium to be Less resistance and the sound would maybe even be louder. This is an experiment worth working further on.

[@oscarfernandez2437]

We need more videos with the professor ! I feel like he have thousand stories to tell !!

[@GiddeonFox]

The attenuation of sound is actually used on rocket upper stages to help dampen vibrations and resonances, though they use nitrogen until right before launch since helium is so expensive :)

[@CanyonF]

Happy Birthday professor!

[@paterfamiles]

I think that helium in driving is to replace nitrogen to prevent nitrogen necrosis (which occurs between 3 and 4 atmospheres at 99 to 132 ft below the surface of water.) And if i am not mistaken nitrogen necrosis happens when the amount of nitrogen that dissolves into the blood Causes an effect that is similar to drunkenness. I also believe that any desolved gas ,because it is under pressure, in the blood can cause the bends. Thats why deep sea diversm must decompress slowly to allow the gases to come out of solution and pass through the lungs un till some sort of equilibrium is attained then decompressed at a slightly lower pressure un till a new equilibrium is attained. This is repeated until the diver submerges from the water. Even then the diver should not fly in a plane for an amount of time or ascend to a high altitude untill there sostem has fully equalized. All the aforementioned is relevant to compressed submarines or chambers. For military submarines and most research submarines the cabins are not pressurized which limits the depths that can be attained by the submarine, so it still has the advantage of being able to surface quickly. I hope this is useful. I always enjoy and am educated by these Great KZbin videos. Thank you!

[@adebowalekonstantinov404]

The reason the iPhone sound was muffled is likely due to the sudden change of density in the two gases. Helium, having about 1/10 the density of air, has sound moving through it then suddenly into the much denser air, causing the sound waves to reflect back into the bag due to a refractive index gradient. It's like being underwater and barely hearing the faint murmur of voices from people outside of the pool, because, just like in the helium example, most of the sound waves are reflected off the surface of the water. It's also why at a certain angle we can have total internal reflection in an air-water boundary (when a water surface acts like a mirror from the inside, just like when looking inside a fish tank at a certain angle).

[@201950201950]

The density of the helium causes the sound to be thinner because it's not as dense. The normal atmosphere oxygen and so on is thicker so it amplifies the waves.

[@detritus10001]

Ah, Louis Armstrong! My hometown hero! One of the only things we have to me proud of in Louisiana, US.

[@k.c.lejeune6613]

Beau Remington I'm from southern Louisiana myself, around the Lafayette area.

[@oldoddjobs]

Self-hating for applause, pathetic

[@lennyface2586]

2 comments

[@williamarmstrong7199]

That is perfectly understandable. 1st thing the speaker is not a resonance cavity or relying on the mass of a gas causing a fibre to vibrate. So the sound will not change in the same way. 2nd the attenuation is due to the reduced mass of helium compared to air. I would hypothesize that if you did the same with Hydrogen gas the attenuation would be 3 Db more than with Helium. Likewise if you put the phone in a denser gas the sound level should increase also.

[@dewetvanrooyen8458]

So nerdy , I love it , thanks for your videos.

[@Malfunct1onM1ke]

My definition of a great day, is seeing another periodic video online with Sir Martyn, Neil and Hard-as-Nails Brady behind the camera :)

[@sethapex9670]

I think because the helium atoms have much less mass than normal molecules in the air, they move around much more quickly in response to sonic vibrations. more of this movement can then be transferred away as heat rather than sound.

[@sethapex9670]

@@benschreyer8295 sure, I was just pointing out this fact to explain why the sound from the phone was more attenuated by helium than air.

[@quistan2]

The cell phone was quieter in the helium for the same reason sound don't travel in a vacuum, and travels long and loud in a liquid, and the same reason you can make a rudimentary telephone with string and plastic cups. If you had a hypothetical solid rod that stretched a thousand miles that you were capable of swinging as easily as a fly swatter with the hopes the end would reach the speed of light, you would find that the solid object would flex in a wave that matched the speed of sound in that solid. Sound travels faster in denser materials but I think requires more energy to resonate them.

[@juicestain1232]

Congrats, 🎊🎉🎈🍾 you have 1,000,000 subscribers!!!!!!!!!!!

[@christiantroy7722]

Thanks for the great videos always helpful and great information I'm not a science student but I like to learn about all these things you show always interesting to watch

[@ZeedijkMike]

You guys are the best. Thanks for yet another great video.

[@s_mores]

I could listen to the professor all day

[@fr89k]

If you ever intend to breathe Helium (or N²O, which is probably a more common thing), NEVER take it directly from the pressurized container. Always put it into a balloon first. Otherwise the pressure from the pressurized container might rip your lungs. And even if this is not happening, the gas cools down while it expands and thus could cool down the lung to a point that also damages it...

[@MichaelHuang1]

Happy birthday, professor!

[@lii1Il]

Sound is muted because a vacuum is the greatest insulator which also reduces sound, and helium or hydrogen displaces air which is denser, thus reducing sound.

[@billygoose3759]

HAPPY 70TH BIRTHDAY POLIAKOFF

[@mizutoryu242]

This was the best music placement ever.

[@roberthayward1140]

I've been thinking about the sound attenuation when a bag of helium is placed over the iPhone. My hypothesis is that the high speed of sound in helium produces destructive interference when the sound waves reach the microphone. This speed increase means sounds re radiating into air from various parts of the bag surface will be slightly out of phase as they reach the microphone. The attenuation of the sound would be a result of destructive interference. Thank you so much for all the wonderful videos.

[@nwarsaleh3037]

Amazing

[@Vrga]

1 million subscribers,congrats :)

[@misium]

Attenuation is still caused by difference in the speed of sound in helium and air. When a wave meets a medium with a different speed of progression, some of it will reflect, and some of it will pass through and refract. It is the same principle as with light and glass - air edge. In the case of a helium closed in a plastic bag, there is the plastic in the bag as well, but its thickness is to small to matter for the wavelengths of the sound we hear.

[@Aviator27J]

Haha I love Neil! Stoic one moment, cracking up or peeking around the corner with a smile the next!

[@dannyfergusson3243]

5:41 @Periodic Videos Its because there is less mass being pushed by the speakers since its lighter and thus it cant hit the plastic as hard so it doesnt pass through as easily

[@fluffyfloof9267]

HeHe, i love how Neil just barely manages to not burst into laughter …how often did you shoot this scene? …so good!

[@BkDelta]

I like when they add exotic chemistry into these videos. It shows the "rules" are fuzzier than most people think

[@sergiosuaza8972]

this channel has reached a million subscribers

[@benw543]

Sound is conducted through air as a preasure wave as the pure Helium inside the bag is alot less dense then the regular atmosphere outside the bag it makes sense that the phone would be quieter inside the bag as there is less gas for the sound wave to proporgate through.

[@RWBHere]

At around 6:00 the attenuation is caused by poor impedance matching between the speaker diaphragm and the much less dense Helium gas. The speakers are optimised for best impedance matching with air; which is mainly Nitrogen and Oxygen.

[@dstpro]

In my opinion the lower speaker volume of the iPhone in Helium is due to acoustic impedance. The air density matches better with the speaker in terms of energy transfer.

[@NoahSpurrier]

I read a story awhile back that stated that exposure to helium can destroy a critical component in smart phones. Helium isn’t reactive, of course, but it’s very small and can permeate through certain materials. I believe the helium was getting into a MEMs component where the lower density of helium would mess up the resonance timing of the micro mechanical device.

[@mateface1313]

6:42 Neil smiled again

[@tonyvertrees3816]

Happy Birthday Sir Martyn!

[@Abitibidoug]

I think the helium attenuated the sound more because of its lower density. It's like if you had the music playing in a bell jar and pumped out some air but not all, the sound would be conducted less efficiently. In a higher density medium sound travels farther. I've noticed that underwater you can hear the sound of a boat propeller from a long distance because sound travels so well.

[@mickelilltroll77]

The pressure amplitude from an acoustic point source is: p = Q* rho *c *k / (4 * pi *r) = Q *rho *f / (2*r) f is the sound-frequency, Q is the volume flow from the source , r is the distance , and rho is the density of the medium/gas. The volume-flow will only change very slightly with densities as low as air or helium, since the mass-loading of the gas is small compared to the moving mass of the transducer. So p ~ rho of the gas more or less.

[@mickelilltroll77]

dB-Level = 20*log10(0.1786 /1.225) = -16.7 dB, where -9 dB equals perceptual a sound that is half as loud (simplified). (See "Fletcher-Munson" curves for a more accurate model of loudness). I predict that the sound-level decreases with 17 dB when you fill the bag with Helium.

[@spamviking8591]

Only time I've ever seen Neil crack a smile.

[@JohnTackman]

Helium is actually used by divers on very deep dives because oxygen toxicity becomes a problem at very high pressures (and therefore high partial pressure of oxygen) and so does nitrogen, so you need to "spread out" the partial pressures to make the gas breathable, helium doesn't become toxic under pressure so the deeper you go, the more nitrogen and oxygen you need to replace with helium. This is called 'Trimix' diving (mix of three gasses). "The bends" is also known as decompression sickness and is the problem of nitrogen bubbles forming in the divers tissues, joints and blood if surfacing too quickly after your dive (dive length and depth and personal physiology determines what is "too quickly").

[@dukebouwer]

Grats on a million subs!

[@FernandoVinny]

6:40 the perfect soundtrack for this scene