View previous topic | View next topic


Page 1 of 1

11731.  Thu Dec 02, 2004 10:09 am Reply with quote

Here's one for Gray (for the physics) and Gaazy (for the music). In the last series I wrote a question for the music special about the possibility of a singer shattering glass or crystal with his voice, a trick which is somtimes attributed to Caruso amongst others. My researches indicated that it was impossible for sound to have this effect unless it was very loud, precisely pitched, and sustained - ie that it couldn't be done by the human voice. Furthermore, I understand that Caruso's widow went on record to deny that he had ever done it (no source for that, though).

Just before the recording, though, two of the researchers said that they had definitely seen it done on TV many years ago. Also, JumpingJack and I together personally witnessed a bizarre moment when a small boy screamed after being bitten by a sheep (as well he might) and the window of the car he was standing next to shattered (my car, as it happens). So we judged the question unsafe and pulled it because we didn't have time to nail it down.

I still think it'd be a nice bit of business, though, having the panel attempting to break glass on the show - so what's the truth here?

Other interesting stuff about Caruso also welcome.

11732.  Thu Dec 02, 2004 10:10 am Reply with quote

The watermelon is a good fruit: you eat, you drink, and you wash your face.
Enrico Caruso (attr)

11742.  Thu Dec 02, 2004 12:58 pm Reply with quote

My preliminary delvings come up with the story of the Memorex tape people, who have often used the human voice to shatter wineglasses as part of their sales demonstrations.

The clincher, however, is that they amplify the recorded voice to about 94dB in order to accomplish the feat. No human voice could do that without amplification, and - as the shattering is caused by a note's frequency (its vibration exactly matches that of the glass) rather than its origin - an amplified mouse-squeak would presumably work just as well.

11746.  Thu Dec 02, 2004 1:11 pm Reply with quote

Well, it's theoretically possible - meaning that there's a well-understood mechanism by which it could happen. This is not to say, however, that it did happen at any point. I can't see why it shouldn't have, though, and here's why.

When you push a small child on a swing, you hardly have to push it at all, but eventually - as if by magic - the child is swinging with gusto, many metres back and forth. This is due to the same phenomenon as glass-shattering. The central concept to note is that a small force, applied at the same frequency as the natural system, will soon make the natural system oscillate wildly.

A child on a swing is basically a pendulum - and as we all know, a pendulum always swings with a regular period, irrespective of how wide it's swinging.
Attempt to push the child with the wrong frequency - e.g. sometimes when it's not closest to you and you'll have no success getting the altitude it seeks (and probably push it off the swing). As a side note, you can get away with pushing it twice as often as you need, and you'll still get the swing going, but be wasting half your pushes, when the child is furthest away. This 'twice-as-fast-ness' is called 'a harmonic', and accounts for the fact that you can get several notes out of, say, a trumpet without using the valves.

Anyway, the same thing applies for any system, really, and an object such as a glass is just another system. The glass's natural frequency is a product of the macro-structure of the object (its shape - i.e. a bell shape for a wine glass) and the micro-structure of the material of which it's made (i.e. the molecular bonds in the glass).

For the glass in question, you can get the natural frequency by flicking it with a finger (any system, when given an 'impulse', will then helpfully resonate at its natural frequency). Then, when you bombard the glass with a force of that frequency (yes, sound waves are a force: a pressure wave propagated through air), it will, if pitched accurately enough, be able to 'pump' the glass system so that it 'swings' more and more until eventually the structure can't absorb the energy in it, and it'll shatter.

If the frequency is accurate - try using a frequency generator and an amplifier - then the volume (also known as amplitude) is not too important. As long as the energy in the sound wave is consistently enough to overcome the energy loss in the glass, the energy in the glass's vibration will build and build, and the outcome is inevitable.

Think of pushing that kid on the swing, just a little bit each time, at exactly the right moment each time, and the outcome is also inevitable: you will, in fact, have to stop pushing after a while to prevent the intervention of the Child Protection Agency...

11768.  Thu Dec 02, 2004 7:18 pm Reply with quote

Similar to all that business about bridges collapsing, either from wind blowing through or from troops marching over in lock-step.

What you have said seems to confirm the view that the trick couldn't be done by the opera singer, though (pace Tintin and Madame Castafiore or whatever she was called) because it's presumably impossible to hold a note that accurately.

11775.  Fri Dec 03, 2004 3:12 am Reply with quote

No - I think Memorex's experiment proves that the note can be held accurately (the glass is pinged with a rubber hammer just before the singer is recorded, to establish the exact pitch); Gray's contribution suggests that the limitations on a live singer would be more in the order of lung capacity, in that he or she would never be able to hold the note long enough.

It would still appear from the Memorex model that a highly-amplified recording of a singer's voice will break the glass almost immediately.

11777.  Fri Dec 03, 2004 4:12 am Reply with quote

Good stuff. Now, about the small boy and the car window - this was a short, sharp shriek and the window just shattered immediately. Do we have to conclude that it was a coincidence that the window broke at that exact moment? This is possible, of course, but there was no other apparent reason for the window to break.

11787.  Fri Dec 03, 2004 12:30 pm Reply with quote

Hmm - I can't think how that might have happened. Unless the shriek was at exactly the window's natural frequency, and it already had a crack in it or something to weaken it. Still a good set of coincidences...

11804.  Fri Dec 03, 2004 6:35 pm Reply with quote

Opera singers also have a disagreeable amount of vibrato, so much of their energies would be wasted. What we need is a nice robust treble.

And that, m'lud, is the case for the defence.

140206.  Tue Jan 30, 2007 2:25 am Reply with quote

This appears to be a long-dead topic... but I thought it would interest people to learn that QI got this one wrong... it IS possible to break glass with the human voice WITHOUT using amplification (or any other aid, for that matter). It was done on US television on the show Mythbusters by the voice coach Jaime Vendera. The clip from the show can be seen on youtube, and Jaime Vendera has images of himself doing it on his website.

140289.  Tue Jan 30, 2007 6:12 am Reply with quote

This is an extremely interestign topic. And here I was thinking it was about David Caruso, highly amusing 'actor'. My mum watches CSI:Miami purely so she can watch him take his glasses off. True. She the superiour CSI:Crime Scene Investigation for the stories.

On topic...

In school we were shown a video of a glass breaking after being bombarded with sound. The glass itself was encased in a box made of (presumably) tougher glass because (so the presenter said) the volume and pitch required would damage the veiwers' ears. They also said that it was impossible for a human voice to break a glass with their voice alone; it would require electrical amplification. I'd concede to Mythbusters on that one though.

The programme was still interesting. They showed the glass when the sound was just below the amplitude that would break it. It wobbled like jelly.

141380.  Fri Feb 02, 2007 6:50 am Reply with quote

I don't know what the highest note it is possible for a normal fully grown male to reach (I'm sure musicologists will enlighten us) but I once read that it has only been captured on recording twice- once by Caruso and once by Roy Orbison.

Any truth or is it back in the ever expanding Urban myth/cock and bull drawer?

141824.  Sat Feb 03, 2007 9:08 am Reply with quote

Are male countertenors included in this attempt for the highest sung note? Andreas Scholl sings some fairly high notes. I've never heard Caruso though.


Page 1 of 1

All times are GMT - 5 Hours

Display posts from previous:   

Search Search Forums

Powered by phpBB © 2001, 2002 phpBB Group