100 thoughts on “Barking Dog (slow motion) – Periodic Table of Videos

  • Taso Gramm Post author


  • JoshwdP Post author

    I suppose it makes sense now that the noise is so loud, because the vibrations must excite the air so it generates sound!

  • Stephen Kile Post author

    That one at 5:32 is the best.

  • DanielBrennan9 Post author

    Delighted to see a review of Professor Poliakoff and his work in Chemistry World this month!

  • Chance Post author

    Wow, Impressive!

  • Robbie Rendall Post author

    its like a pulse jet

  • Emma Messinger Post author

    I have a different theory, I believe the gases in the bottom become so compressed under the energy and force that it thickens to the point where the fire can't ignite it all at once, this is also helped by the small diameter of the pipe, and the noise is actually created due to oxygen or other gases trying to escape the tube all at once. I noticed an almost vacuum effect towards the bottom, it'd be interested to see if this experiment still worked the same on a larger scale and would also like to see the barking dog in slow motion but from a bottom view looking up to see if the fire has a inward dip on it. 

  • Cooper Gates Post author

    Each time a pressure wave shoves down to the bottom, you can see drops of CS2 condense on the inner wall of the tube and evaporate again once the pressure drops.

  • Ricki Nielsen Post author

    It is a bit a matter of chemists trying to understand physical systems.

    If you didn't think this (or similar) pulsing took place, where would you expect the sound to come from? Something have to create oscillating pressure waves, else it would just have been a pop.

  • Navik Shah Post author

    it would be good to see if it can be controlled with sound and even if it can be paused in the middle

  • Benny Heflinger Post author

    When I listen to my dogs bark (actual dog) audio recording and look at it on an oscilloscope, if you were to zoom in on the wavelength you can see the individual vibrato patterns.  I love this because this is like a visual version of just that!  The amount of vibrations in the sample and the shape in which is vibrates determines the way it sounds, for example…sine wave shapes determines the resonance (the acoustics of the sound) and the amount of vibrations/cycles/hertz in the given second of the sample determines the pitch.  This initial sound is probably about 140hz but I wouldn't be surprised if you would get different sounds out of different sizes and shapes of tubes. =)

  • Tord Magnus Dyrkorn Post author

    Warning: This video contains Michael from Vsauce.

  • Alex Mackay Post author

    Hi everyone. What's the purpose of doing this science experiment? I'd love to do this in class. 😀

  • Kyle Carmichael Post author

    I love that something done so often is able to provide such a great learning experience, not just to us non-scientists but even scientist, learning shouldn't stop and it doesn't stop, well done well done indeed!!

  • Alex Post author

    I love blue fire

  • Sam Chapa Post author

    Why not do a secondary experiment? Use different sized test tubes (widths and lengths), an oscilloscope w/microphone and test for sound pressure level and frequency differences to see if the flame front vibrations correlate with sound frequencies produced. Might be a fun experiment.

  • TheTimtam112 Post author

    His mini-me lego figure on the globe has a really quite demanding likeness 

  • Mwyann Post author

    This guy has the most boring screensaver ever.

  • TheAnonymmynona Post author

    it would be nice to test the theory
    you clould for example place a verye fast working presure measurement device (i dont know the right english word) at the bottom

  • Matthew Coleman Post author

    if we have different lengths of tubes does the frequency of sound change? if so then if the frequency resonated with the glass you could break the glass.

  • katuroo Post author

    could tonal rods be placed in the tube – maybe one in the middle not touching the sides going all the way up to the top / to produce different sounds? would the rod then vibrate a frequency that would break the tube?

  • James Klett Post author

    any relation to a type 1 supernova?

  • Bruce Webster Post author

    I think it may be an effect of the mass of the gas flowing from the top of the tube. As the burning gas leaves the top of the tube its momentum is acting like a plunger and drawing the flame front upwards and lowering the pressure of the gas below it. Hense why you see the vapour form. This will only last a certain length of time until the pressure drop is enough to draw the flame front downwards. This would set up an oscillation, very similar to the one that is used in pulse jets. The frequency change could be related to a perhaps decreasing density and hence mass of the material in the tube, or that the reduction in unburnt fuel changes the pressure/volume relationship of the system in effect changing the 'spring constant'

  • BloodySeaGulls Post author

    Man I love experimental science.

  • Lolo Bergkamp Post author

    If look at this video with english subtitles, you have a funny mistranslating at the 1:46 mark.
    instead of "races to the bottom" you have "racist obama"

  • Postghost Post author

    What is the fallout at 1:46?

  • Aden B Post author

    Uh-oh, somebody didn't give vsauce any credit…

  • Kasriel Lewis Post author

    Would be interesting to hook up a pressure sensor a the bottom of the tube and sample at the same or close to the same speed as the high speed camera as well as maybe hooking up a microphone and sampling that as well and see how all three pieces of data correlate as well as to verify the correctness of the professors hypothesis.

    Either way very cool, thanks 

  • john sherdahl Post author

    My guess , just like plain fumes in a container are more highly flammable then a heavier gasses , when the actual gas in the tube starts to burn , it gives-off a lighter burn-off secondary gas , and when the flame gets pushed-up by the pressure , it resences the lighter burn-off fumes from the original burn off of the original gasses , inturn does a multiple reaction effect from each of these processes burns !…

  • Nathan Hunt Post author

    Whoever edits these videos has a great sense of humor.

  • Wayne Dollery Post author

    Could you measure the 'beat frequency' of the reaction by correlating the sound of the reaction to the slow motion video?

  • Jetman640 Post author

    I have knew about the reverb back when I was around 10 or 11, having done this with some butane or alcohol and a milk bottle or pop can, and though not as magnificent you get about the same result as the air fuel ratio gets right.

  • Slurpon Muhdick Post author

    Its a pulsejet engine.

  • Irval Firestar Post author

    Hm, if you look closely at the bottom part of the test tube thing during the slo-mo you can see condensation forming during every circulation and then disappearing just as quickly.

    Another proof of it being a pressure wave from the flame front, I guess?

  • TaLorde Hornbro Post author

    I used to do this all the time at my friends house as a 10 year old. He had a weight bench. The weight bar was 5 or 6 feet long and hollow. I'd spray a generous amount of aerosol deodorant on one end thrown light it on fire. Id then spray more deodorant thru the tube, but from the opposite end. The fire would spray out the other end violently. Then receed as a "fireball" back into the tube, all the way thru and shoot out the other end. It made the exact same sound generated by your barking dog demonstration.

  • Dom Brazzale Post author

    It looks like the pressure waves are creating vapor below the flame if you look closely.  The vapor even travels downward to the same rhythm of the wave.

  • Darkavatar Post author

    It sounds awesome in the slow footage…

  • Alex Proshkin Post author

    I knew this because of Vsauce

  • Alastair Corsair Post author

    Very lovely blue, reminds me of, Cherenkov radiation, you guys should talk about that one sometime.

  • Ghost Emblem Post author

    First time on this channel, the format is reminiscent of numberphile

  • Snankz Post author

    "If you want to understand how the universe works, one may think in terms of vibrations, frequency and energy." As you can see the flame vibrates. Think of that, the first phrase is from Nikola Tesla. Put your head to think. XD

  • meetn2veg Post author

    If you feel it of value, perhaps several pressure gauges or indicators could be moulded at regular intervals down the length of the tube to show, over a few experiments, just what sort of pressures this reaction is making.

    I'm sure that even the final graph of time/mbar would even be fascinating.

  • SoundMaster Post author

    sounds more like a muscle car

  • Julien Post author

    Hi 9gag 🙂

  • jem laey Post author

    Also notice how when the pressure wave reflects off the bottom of the tube and is coming back up, it pushes through the flame, again pushing it up, but look at the top of the tube: some of the flame gets pushed out of the tube each oscillation. Very cool indeed

  • Mica Santos Post author


  • Nick Pollard Post author

    Does anybody know where the BD Shaw footage came from, and whether there is any more of it available?

  • RaynaDJ Post author

    This is arguably my favourite ever sound.

  • GiggitySam Entz Post author

    If you like the reaction in slow motion as well, Thoisoi2 made a video about it, look it up ^^

  • Shehab Ellithy Post author

    I noticed Micheal from Vsauce. Someone confirm.

  • HAISPAM Post author

    I don't think the pressure wave is bouncing off the bottom of the test tube, but rather off of the gas beneath the reaction. You can see it being pressed down with each "stage".

  • life42theuniverse Post author

    I was thinking at first that's really cool… then I realized if there wasn't some kind of oscillating pressure there wouldn't be anything to create a sound.

  • Codenwarra Cove Post author

    Stinks and bangs

  • DippnDonuts Post author

    I never knew Albert Einstein was still alive 😂

  • Vincent Russell Post author

    star wars sounds?

  • AmarthwenNarmacil Post author

    So, is the sound actually the pressure wave and not the flame itself?

  • gorillaau Post author

    Supposing you inverted the tube, such that you light the bottom of the tube??

  • Guilherme Francescon Cittolin Post author

    Had one ever tried to measure the speed of the flame front and the shock wave, so we could check how close we get to the speed of sound?

  • Jake Quinn Post author

    Is this reaction linked to pulse jets in any way? What would happen if you put a valve/spark plug at the bottom of the large test tube, and kept the ignition going by adding 3N20+CS2?

  • Rishav Koirala Post author

    5:24 Is that who I think he is?

  • bluierox Post author

    The first man looks like science

  • andre Post author

    it sounds like a lightsaber lol

  • TheNeonOutlaw Post author

    You gents got a link to Colonel Shore's lecture?

  • Celt Gunn Post author

    Always wows me seeing the brilliant blue flames chugging up out of the tube. I love seeing the blue flame at the bottom pulsing as the fuel burns down the tube. 👍

  • bhull242 Post author

    I actually expected this from the earlier videos. For one, a rapidly, smoothly moving flame in a tube probably wouldn't make that sort of sound. It makes more sense for there to be oscillating shockwaves. For another, I could see a series of flashes as the flame traveled downwards, which suggests that the flame's motion isn't as smooth as it appears. Plus, at the end, you sort of see the top of the flame rapidly changing in length.

  • Mikkaa 19 Post author

    + Periodic Videos hi, could you ask one of your physicist friends what would the fromula for the acceleration of the flame front in such reactions after it reaches speed of sound be? that is, when the mixture is ignited from the open end and the other one is closed. I looked literally everywhere but i cannot find this info and im certain it was something impressive!
    It would be awesome if ou answered, i love your videos!

  • Dylan Rohrback Post author

    If I might ask, what chemicals in the reaction causes that bright blue flame? Just for curiosity's sake.

  • deathsChemist Post author

    i kinda get the feeling that these oscillations are what causes the sound, you know what i mean? of course the sound gets higher as the flame goes down the tube, it's causing pressure waves at a greater frequency.

  • Cracked Emerald Post author

    Did anyone else see the weird circular cloud that appeared at the ceiling at the end of the experiment?

  • ARDEACT Post author

    5:25 That sounds like a pretty loud V8 (Earrape warning)

  • Seth Apex Post author

    we kind of should have expected something like this, if the flame rushed smoothly down the tube it shouldn't make such a loud sound, if any. Sound comes from the vibration of air, so unless the vibration were coming from the tube itself for some reason, we should expect the flame to vibrate like that.

  • Julian Lin Post author

    Turn your volume down
    This is awesome

  • Otakutaru Post author

    So, is this "oscillation" of pressure the ascending roar we hear? It could be actually fun to calculate it if we knew the frames per second of the footage, and then correlate it with the pitch of the sound we would hear at 100% frame speed… I guess.

  • Donald Sleightholme Post author

    i think if you could keep the reaction going and surround the tube with photovoltaic panels then you would a new way to generate electricity. 🤔

  • Ted Dwiers Post author

    try an inlet vent…
    see what happens with that!!

  • J. Han Post author

    In the beginning it looks like a will o' wisp or ghost light found in many cultures. So pretty.

  • MadZ Post author

    Strange you didn't mention the correlation with SOUND…I guess the increasing of the speed of the oscillations is the increasing in the peach of sound…Why not to COMPARE the flame oscillations with the sound wavelenght and frequency? =)

  • ian kleinschmidt Post author

    ad some trumpet-like shape piece to it so it sounds even more scary 🙂

  • superdude123032 Post author

    That's where the sound comes from, isn't it? The pressure waves bouncing back and forth?

  • IamJiva Post author

    some more wonder youtu.be/FSdBB1vBDKY ("Platinum Catalysis" youtube video)

  • Jairdon Porter Post author

    Sound more like a car like a 488

  • adam podlofsky Post author

    Is there any reason why one could not generate the barking dog "effect" (the descending flame and the whoosh sound) with any volatile flammable mixture in a long tube? Is there something unique about the nitrous oxide + carbon disulfide reaction that makes it work, or makes it work better?

  • Peter Walker Post author

    Oscillation = sound.

  • Amrit Post author

    What if you pour lean air fuel(petrol or alcohol) mixture in the tube and light it ?

  • Joseph Burgis Post author

    what happens if you purposely vent the bottom of the tube?

  • Mark Hodgson Post author

    Looks like a pulse jet

  • Mark Hodgson Post author


  • Kickemall1964 Post author

    I guess the sound it makes comes from pushing air out of the tube.
    It explains the sound going up in pitch.
    Couldnit the effect come from a shortage of oxygen.
    It belches the burned gasses and gets its next gasp of air into the tube.

  • Pedro Pinheiro Post author


  • James Petersen Post author

    Have you compared the change in frequency of the oscillating flame front with the audio waveform? I'm curious if the rising pitch of the barking sound is causally related.

  • Matthew Jackman Post author

    I wonder how this experiment would work with a variable pressure release valve on the bottom of the tube (pretty bloomin well attached might I add)

    The barking sound could become completely different as I imagine it occurs due to those oscillations .

  • Domenic Perito Post author

    lol the oscillation is from the sound cause by resonance

  • Domenic Perito Post author

    its at the frequency of the sound you hear

  • Ryad Arlan Post author

    I dont see the point of this or why so much time is spent showing it. Its the smart ones that frustrate me.

  • Tsetsi Post author

    Dogs that bark dont bite

  • Benjamin Newlon Post author

    Dog? More like trombone blast.

  • MrWombatty Post author

    More proof that chemistry & physics are undoubtedly linked!

  • Koolaid Black Post author

    "It involves a test tube, a really big test tube.. this is just a model" No one commented on that great joke? Come on

  • The Conservative Dude Post author


    Gotta love the professor

  • Bradford Mailloux Post author

    I know it's an old video, but have you guys ever considered putting an electronic pressure sensor inside to record the pulses? You could have one stuck into a cork plugging a tube that has both sides open (like the extra long one).

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