How Do Slient Sounds Break Glass?

[Bartmanhomer]

I was watching CSI: NY and there was a bank robbery that the robbers who dressed like Holly Golightly look-alikes rob a jewelry store used a device with a silent sound capable of breaking glass. I was so amazed at how did they do that? How did a silent sound be able to break glass?

[hamishspence]

Maybe it's ultrasonic or infrasonic - only silent to human ears?

[akma]

Human ears only hear sounds in certain ranges (generally 20-20,000 hertz), and since it broke glass, I'm guessing it was higher pitched.
Although I wouldn't trust the science used in CSI, I'd say it's plausible.

[Khedrac]

Scientifically speaking "sound" is pressure waves in the air (or other medium).

(Philosophically speaking sound is what you hear, hence the tree falling question.)

Sticking to science, because you said CSI:

There are two ways to break glass with a pressure-wave - one is to apply more pressure than the glass can take - this is mainly things like explosive pressure wave fronts, but I suspect a sonic boom is also this.
The second is to oscillate the glass at it's resonant frequency (or something close to it) and at this point that usually takes a lot less direct energy. This is how a very few singers have been able to break wineglasses.

As the other posters have said, it is very likely that the frequencies involved would be out of human hearing range (and possibly most animals - to avoid a lot of barking dogs).

A "silent sound" effectively combines the two definitions - it is silent (philosophically) and sound (scientifically).

[halfeye]

I don't think it's possible.

[BisectedBrioche]

I don't think it's possible.

It's actually quite possible.

When a piece of glass makes a ringing sound, it's basically vibrating and producing the sound. The same sound played back will conversely cause it to vibrate; if you do it loud enough it'll do so with enough force to shatter.

https://www.bbc.com/future/article/2...ass-with-sound

[snowblizz]

When Mythbusters tested breaking glass with sound there was only not too loud hum coming from the speakers IIRC. When they had the human singer do it, aided and unaided it was a lot louder.

Similarly when they were testing if there is a brown note the speakers were pumping out such a low frequency no human could hear it.

Then again the CSI series gives the appearance of science but that's all it does. Grab a big bag of salt when watching it. The principle of the idea is sound (), but it is likely the way they actually presented it in the show is fantastical.

[halfeye]

It's actually quite possible.

When a piece of glass makes a ringing sound, it's basically vibrating and producing the sound. The same sound played back will conversely cause it to vibrate; if you do it loud enough it'll do so with enough force to shatter.

https://www.bbc.com/future/article/2...ass-with-sound

Right, but that sound is going to be audible. When the glass breaks, if it breaks, you will hear the sound of breaking glass.

[Keltest]

Right, but that sound is going to be audible. When the glass breaks, if it breaks, you will hear the sound of breaking glass.

Well if thats the standard youre going by, what you want is a blast of sound so loud that your eardrums immediately explode, followed by, i dunno, somebody smashing a glass with a speaker or something.

[Willie the Duck]

Right, but that sound is going to be audible. When the glass breaks, if it breaks, you will hear the sound of breaking glass.

I think you are both right for how you think the situation is being framed. I don't think anyone else thought that the glass-break was silent, only the sound that caused the glass to break. Only the OP can answer the question with regards to the show in question.

And to the OP -- just remember that CSI is hot-buttered garbage with regards to both how science works and how forensics/criminal justice work.

[GloatingSwine]

Glass can be broken by sound waves at its resonant frequency. As each "wave" of sound arrives the vibration the last one created in the glass object is reaching exactly the same peak and so more and more energy keeps getting added to the vibration until it overcomes the structural strength of the glass.

It takes about 120dB within about half a Hz of the resonant frequency to break a wine glass.



That said, the CSI example is bunk for a number of reasons:

1. The resonant frequency of glass is within the audible range of human ears (typically about 550-700Hz depending on the glass).

2. It only really works on very thin bits of glass (that's why they always use wine glasses).

3. Jeweller's store display cases will be made of tempered or toughened glass, which don't have a uniform structure due to the way they've been treated and so won't have a uniform resonant frequency, meaning that the inner layers will damp the vibrations of the outer and cause the resonance effect to disappear.

[Peelee]

When Mythbusters tested breaking glass with sound there was only not too loud hum coming from the speakers IIRC. When they had the human singer do it, aided and unaided it was a lot louder.

Similarly when they were testing if there is a brown note the speakers were pumping out such a low frequency no human could hear it.

Then again the CSI series gives the appearance of science but that's all it does.

Amusingly enough, Mythbusters also gives the appearance of science!

[Keltest]

Amusingly enough, Mythbusters also gives the appearance of science!

I will defend the Mythbusters approach to science with my dying breath.

...except for the part where they almost killed themselves because they forgot to properly secure a cannon. Thats not something that needs repeating.

[GloatingSwine]

Amusingly enough, Mythbusters also gives the appearance of science!

Until they get bored, then they explode something.


Although on the note of volume, a pure low tone at 120dB is not going to be perceived as "loud" as a high tone at the same volume, and a human singer is going to have a lot easier time maintaining the volume at a higher tone.

[Bohandas]

The sound has to be a multiple of the frequency the glass naturally vibrates at when tapped. This will cause the energy imparted by the sound to resonate inside of it and gradually build up (as long as sound keeps being applied) until so much energy has built up that the object bursts.

(This can also be achieved by lightly tapping an object at the object's natural frequency, which was the principle behind Nikola Tesla's "Earthquake Machine")

I will defend the Mythbusters approach to science with my dying breath.

Same here. Except for the part where they made an abandoned bridge preceptibly shake with the aforementioned earthquake machine but then declared the machine busted because they're Californian and apparently don't count something as an earthquake or earthquake-like unless it's at least 5 or 6 on the richter scale

[Keltest]

The sound has to be a multiple of the frequency the glass naturally vibrates at when tapped. This will cause the energy imparted by the sound to resonate inside of it and gradually build up (as long as sound keeps being applied) until so much energy has built up that the object bursts.

(This can also be achieved by lightly tapping an object at the object's natural frequency, which was the principle behind Nikola Tesla's "Earthquake Machine")



Same here. Except for the part where they made an abandoned bridge preceptibly shake with the aforementioned earthquake machine but then declared the machine busted because they're Californian and apparently don't count something as an earthquake or earthquake-like unless it's at least 5 or 6 on the richter scale

Its been a while since i saw the episode, but werent they on a suspension bridge, IE one designed to move and shift rather than hold rigid?

[Eldan]

When Mythbusters tested breaking glass with sound there was only not too loud hum coming from the speakers IIRC. When they had the human singer do it, aided and unaided it was a lot louder.

Similarly when they were testing if there is a brown note the speakers were pumping out such a low frequency no human could hear it.

Then again the CSI series gives the appearance of science but that's all it does. Grab a big bag of salt when watching it. The principle of the idea is sound (), but it is likely the way they actually presented it in the show is fantastical.

I mean, the Mythbusters also showed that they had to select already flawed wineglasses first, as it didn't work on all the glasses. And giant plate glass is probably a bit harder than some crystal wineglass.

[arimareiji]

Something that might be food for thought to weirdos who think as far out of the box as I often do:

We see a certain spectrum of light. (Other species see different spectra, and for that matter perceive different ranges of sound, but let's leave that alone.)

We can't directly perceive UV light, although we can see the result of it striking surfaces that then shine in the visible spectrum.

UV light can still sunburn us all the way to purple, as I discovered one weekend when I fell asleep at the beach with a friend.

Our ability to perceive a form of energy directly doesn't impact its ability to cause effects that will occur independent of our perception.

[Peelee]

I will defend the Mythbusters approach to science with my dying breath.

Mythbusters is a great TV show. Everyone on it was an amazing engineer.

**** scientists, though.

[Keltest]

Mythbusters is a great TV show. Everyone on it was an amazing engineer.

**** scientists, though.

Only if you assume their goal is to write a research paper.

"This seems strange, lets try and find out more!" is the most fundamentally scientific attitude you can possibly have.

[Peelee]

Only if you assume their goal is to write a research paper.

Not at all; also if you assume their goal is to conduct experiments. Which, unless I've been watching some other Mythbusters, is the entire premise of the show.

"This seems strange, lets try and find out more!" is the most fundamentally scientific attitude you can possibly have.

I wholly agree! Of course, there's a lot of room between attitude and execution. Again, I'm not saying the show wasn't good (it was), or that they weren't fantastic engineers (they were). I'm saying the show was not scientific. It doesn't make the show less entertaining. It doesn't make the people worse engineers. It doesn't lessen anything at all about Mythbusters. And yet there's always pushback, which I have to note never actually contains any arguments on how it actually is scientific.

Hell, it's not even like it couldn't be scientific! There's scientists who shoot chickens out of a cannon at planes! The difference between those people and the Mythbusters crew is that those people are actually doing it scientifically, which is lengthy, detailed, and incredibly well-documented, while the Mythbusters crew just kind of throws some stuff at the wall and sees what sticks. Which, again, makes for a great show when done by great engineers.

[Mechalich]

Not at all; also if you assume their goal is to conduct experiments. Which, unless I've been watching some other Mythbusters, is the entire premise of the show.

I wholly agree! Of course, there's a lot of room between attitude and execution. Again, I'm not saying the show wasn't good (it was), or that they weren't fantastic engineers (they were). I'm saying the show was not scientific. It doesn't make the show less entertaining. It doesn't make the people worse engineers. It doesn't lessen anything at all about Mythbusters. And yet there's always pushback, which I have to note never actually contains any arguments on how it actually is scientific.

Hell, it's not even like it couldn't be scientific! There's scientists who shoot chickens out of a cannon at planes! The difference between those people and the Mythbusters crew is that those people are actually doing it scientifically, which is lengthy, detailed, and incredibly well-documented, while the Mythbusters crew just kind of throws some stuff at the wall and sees what sticks. Which, again, makes for a great show when done by great engineers.

Mythbusters was plenty scientific, what it was not was rigorous. Mostly they took a lot of ideas from popular culture, translated them into scientific hypotheses, and then did initial tests. Their experiments were often lacking in precision and accurate measurements and they had very little, if any repetition for what they were doing (though that's mostly related to the fact that they were making a TV show, not trying to get published).

In many ways Mythbusters operated at the level of late 18th, early 19th century scientific rigor, only using modern tools and equipment (especially explosives). You couldn't do a statistical analysis on basically any experiment they conducted but in many cases the results were sufficiently obvious that they could offer conclusions anyway.

It is absolutely possible to conduct low-rigor science and achieve useful results - most commonly the result of 'promising, investigate with more rigor.' Now, in the 21st century it is generally no longer possible to do this in terms of physics or chemistry with regard to anything at all commercially applicable, mostly because all such pioneering work was done centuries ago. The whole point of Mythbusters was to instead investigate eccentric possibilities where no one had bother to do this before (or at least no one had bothered to do so on record).

[Willie the Duck]

And yet there's always pushback, which I have to note never actually contains any arguments on how it actually is scientific.

Peelee, you haven't make any actual arguments about how the show isn't scientific, despite you being the one to make a claim. Please do not be the guy to wear the badge of burdensome outspokenness because others haven't carried your water for you. I have too much respect for you to let that go unchallenged.

That said, you are correct -- Mythbusters is predominantly a engineering experimentation show, designed mostly around questions vaguely like 'how does such and such a basic applied science concept play out in real life in a given (apparently 'myth'-like) situation. It rarely delves deep into base scientific principles or anything like that. Science is not the primary wheelhouse of the show, so much as engineering. That's leaves open whether it is '**** scientists' or not.

[arimareiji]

I wholly agree! Of course, there's a lot of room between attitude and execution. Again, I'm not saying the show wasn't good (it was), or that they weren't fantastic engineers (they were). I'm saying the show was not scientific. It doesn't make the show less entertaining. It doesn't make the people worse engineers. It doesn't lessen anything at all about Mythbusters. And yet there's always pushback, which I have to note never actually contains any arguments on how it actually is scientific.

Hell, it's not even like it couldn't be scientific! There's scientists who shoot chickens out of a cannon at planes! The difference between those people and the Mythbusters crew is that those people are actually doing it scientifically, which is lengthy, detailed, and incredibly well-documented, while the Mythbusters crew just kind of throws some stuff at the wall and sees what sticks. Which, again, makes for a great show when done by great engineers.

YMMV, but to me it often seemed they were more determined to reach an entertaining and/or pre-ordained conclusion than to conduct probative research. Personally, I far prefer channels like Smarter Every Day -- they may take longer to figure something out, and it may not be a compelling "mystery solved", but they always leave you feeling like you actually learned something and can be confident that any answers reached are full truth rather than an incomplete and possibly misleading truth.

And they built a cannon capable of shooting a baseball past the speed of sound. XD

[Willie the Duck]

YMMV, but to me it often seemed they were more determined to reach an entertaining and/or pre-ordained conclusion than to conduct probative research.

The certainly clearly knew what would happen before trying any number of their experiments. I remember them doing a 'could you surf on a wave produced by exploding dynamite in a pond' and thinking 'I know you know how much energy is actually in a stick of dynamite. You have got to know the answer already, yet here we are because you get to blow stuff up.'

[Bartmanhomer]

I've heard of Mythbusters but I've never watched the show before.

[Keltest]

YMMV, but to me it often seemed they were more determined to reach an entertaining and/or pre-ordained conclusion than to conduct probative research.

I mean, they were. A vast majority of the time, they were trying to achieve a particular result. That was sort of the entire premise. They were very much asking "can we do this specific thing" rather than "what happens if we do X".

One that comes to mind is the "knock your socks off" episode. They very much went beyond the realm of plausible human forces and conditions to achieve it, but the forces involved WILL pull socks off feet if you apply them in the correct proportions. Its just not something a pair of humans will ever do outside of deliberate lab conditions.

[Tyndmyr]

Then again the CSI series gives the appearance of science but that's all it does. Grab a big bag of salt when watching it. The principle of the idea is sound (), but it is likely the way they actually presented it in the show is fantastical.

This, definitely. The science on there is basically what you'd get if someone who wasn't a scientist googled randomly for cool ideas that sounded sciency, read the first paragraph, and then invented the rest in order to get a cool show.

It's...pretty rough in terms of accuracy.

[Peelee]

Mythbusters was plenty scientific, what it was not was rigorous. Mostly they took a lot of ideas from popular culture, translated them into scientific hypotheses, and then did initial tests. Their experiments were often lacking in precision and accurate measurements and they had very little, if any repetition for what they were doing (though that's mostly related to the fact that they were making a TV show, not trying to get published).

In many ways Mythbusters operated at the level of late 18th, early 19th century scientific rigor, only using modern tools and equipment (especially explosives). You couldn't do a statistical analysis on basically any experiment they conducted but in many cases the results were sufficiently obvious that they could offer conclusions anyway.

It is absolutely possible to conduct low-rigor science and achieve useful results - most commonly the result of 'promising, investigate with more rigor.' Now, in the 21st century it is generally no longer possible to do this in terms of physics or chemistry with regard to anything at all commercially applicable, mostly because all such pioneering work was done centuries ago. The whole point of Mythbusters was to instead investigate eccentric possibilities where no one had bother to do this before (or at least no one had bothered to do so on record).

What you describe as scientific-but-not-rigorous also fits perfectly for divining Aristotlean physics - a seemingly good but wholly incorrect way to calculate things. This is hardly the fault of Aristotle, who was quite possibly the smartest man to be wrong about just absolutely everything, but in the modern age that simply doesn't cut it. Rigor is required for science. No rigor is no science. That's the equivalent of people in Facebook saying "do your own research!" and equating googling for a half hour to be "research".

Mythbusters is fun, entertaining run by excellent engineers who took many a science class and are damn well versed in chemistry and physics, and who aim to see if they can more or less conform or nullify a belief. The "more or less" part knocks it out of being scientific.

And if you think scientists in the 18th century were being about as scientific as the Mythbusters crew, I think you are doing those scientists a disservice. Our greatest accomplishments as a people have been due to our ability to predict what will happen if we do X, which is the basis of all science. We truly do stand on the shoulders of giants, and diminishing them diminishes us all.

Peelee, you haven't make any actual arguments about how the show isn't scientific, despite you being the one to make a claim.

Now that is a fantastic rebuttal! Short version, they don't follow any scientific rigor or use the scientific method. I've never found the claim of "that show isn't scientifically proving anything" to be a knock against them any more than "that show is not animated" would be; it's a simple statement of fact that just days "they weren't trying to be that though". And while yes, your issue that I never said why absolutely has a buttload of merit, I do still stand by my claim that whenever I say that it's not scientific, almost invariably people respond by trying to bring scientific methods down to the way Mythbusters operates instead of trying to elevate the way Mythbysters operates to the level of scientific methods.

[arimareiji]

I mean, they were. A vast majority of the time, they were trying to achieve a particular result. That was sort of the entire premise. They were very much asking "can we do this specific thing" rather than "what happens if we do X".

One that comes to mind is the "knock your socks off" episode. They very much went beyond the realm of plausible human forces and conditions to achieve it, but the forces involved WILL pull socks off feet if you apply them in the correct proportions. Its just not something a pair of humans will ever do outside of deliberate lab conditions.

Thank you for expressing what I was trying to get at, much better than I did. (^_~)°

We might disagree, but that never bugged me... but to me it seemed like on rare occasions the converse could also happen. I.e. if it was more entertaining to "bust" a possibility, sometimes they would push the envelope to make it not possible.