|
| | Jaime Vendera, the vocal power house that breaks crystal with nothing but his voice, has graciously allowed Mythbusters Fan Club access to his great interview with Roger Schwenke, the staff scientist for Meyer Sound. Roger has helped out the Mythbusters before - remember the ducks - and has been named an Honorary MythBuster by the guys! So sit back and get into the mindset of the guys who made this episode happen! Thanks Jaime!
Jaime Vendera, vocal coach extraordinaire with Kari at M5Industies
Used With Permission
| |
ROGER SCHWENKE
STAFF SCIENTIST
FOR MEYER SOUND
Roger Schwenke is the staff scientist for Meyer Sound, a professional sound company who handles the sound requirements of artists such as K.D. Lang and Celine Dion. Roger was present in both New York for my Good Morning America and in San Francisco for the MythBusters episode. Here are the views from a scientist’s point of view on the art of breaking glass.
Jaime: Roger, good to hear from you again. Let’s start this interview by learning a little bit about your background.
Roger: Well, I grew up in Woodbridge,Virginia, which is a suburb of DC, and I went to the college of William and Mary in Williamsburg VA., which is in Williamsburg Virginia. I got a Bachelors degree in physics.
Jaime: So how did you end up at Meyer Sound?
Roger: Well, like a lot of physics majors, I had big dreams of solving the grand unified theory and all that sort of thing, and of course, being a heavy metal guitarist. Ha-ha. And I realized that these things were incompatible. A friend of mine went to Penn State, so I decided to go there. Then I got my P.H.D. in acoustics at Penn State doing targeted fusion for sonar. Then I got interested in signal processing, because the Navy is one of the biggest funders of graduate work in acoustics. There aren’t many others. After I got my P.H.D., my first job was here at Meyer Sound.
Jaime: How long have you been there?
Roger: Four Years.
Jaime: Can you explain the physiology of shattering a glass with the human voice?
Roger: Objects have different resonant frequencies depending on their shape. They are also more or less resonant depending on other properties and chemistry. There are wine glasses that you can rub or tap and they will play a really loud note, and there are other objects that you can tap on that won’t produce much of a note. They still have resonant frequencies, but they are very damped. Like a pillow is damped; it doesn’t make much sound. So a glass has exceedingly low dampening and has huge resonant frequencies. So you can play it and it will resonate, and the glass is physically moving, and it’s moving the air, then you hear that pitch. The way that we are breaking the glass; is that we are creating sound and the sound is moving the glass. This is called reciprocity. Since the glass can create sound, we can create sound which will force the glass to move.
Jaime: So, once the glass reaches it’s threshold, it breaks?
Roger: The glass has some maximum strength. Once you get the glass to bend or move past a certain amount, it will eventually break.
Jaime: Jim Gillette told me that if the glass is 550.4 hertz, and I hit 550.3 or 550.5 hertz, it wouldn’t break. The pitch has got to be dead on. When you were doing your analysis, did this seem to be the case or was there any play in that area?
Roger: I found almost the exact same sensitivity. The less damping something has, the more specific you have to be about the frequency that will get it to move. If a glass was 550.3 hertz, I could be sitting there using the computer and frequency generator and tuning in to 550.2 hertz, and the glass would be shaking and the straw would be dancing but the glass wouldn’t break. But as soon as I moved that frequency by .1 hertz…Bang! It would break.
Jaime: So when you got it to the exact frequency, what would you say was the lowest amplitude possible for shattering these glasses?
Roger: That depended very much on the glass. Eventually I got pretty good at breaking them, such that, I would turn it on and they’d break so fast that I couldn’t even measure the sound level, because the sound of the glass breaking was louder than the sound that broke the glass.
Jaime: Overall, did they vary that much per glass? Were they roughly 90 decibels, 100 decibels? Did you have any data to go off of?
Roger: I guess the lowest I can say that I reliably measured it was 105 decibels. That was your voice at 105 dB, and the speaker can go up to 135 dB. If I understood more about what it takes to break a glass, it might be possible to break them at lower than 105 dB.
Jaime: Are you still baffled? Are you still working with figures?
Roger: Unfortunately, there is not a huge market for glass shattering devices. Ha-ha. I’m working on some methods that use gravity. I think it’s going to be more efficient, and cost effective that way. I have one or two theories left that I haven’t tested yet. So maybe enough people will watch the show over and over again and ask me the question, “why do you need the hole in front of the speaker?” Then I’ll get annoyed and have to come in on the weekends, and bust all the glasses the MythBusters left me and figure it out.
Jaime: Do you remember what my top decibel level was in New York? I think you told me it was 100 decibels.
Roger: Yeah, right. The opera singers were singing around 90 dB, and you were above 100 dB.
Jaime: When we auditioned the opera singers, did it really seem that loud in the room we were using at the Discovery Building? I’m so used to my loud voice that it doesn’t really bother me. To me it didn’t seem that loud.
Roger: Yeah, it was pretty loud. All of the opera singers took a step back (ha-ha) when you were really belting it out. Although we were using a speaker, you were noticeably louder than all of the other singers.
Jaime: What assumptions or correlations did you make between the glass I was shattering and my voice. I remember measuring all of those glasses in New York the night before Good Morning America and you were saying that it didn’t make any sense because I was breaking glasses that you thought would be harder for me, and having some difficulty on ones you figured would be easier.
Roger: There were some glasses that seemed to be more damped than others. So, that means it would take more energy to break them, but you could be a little less precise about the frequency. Then there were some glasses that were less damped, and, they would take less energy to break them but you had to be more precise about the frequency.
Jaime: So, apparently there wasn’t a pattern developing?
Roger: Well at first I thought that it would be easier for you to break the less damped, because they would take less energy overall, you just had to hit the note exactly right. It seems that I was wrong, because in New York, it was easier for you to break the more damped. You could definitely sing loud enough, but if you were slightly off of the frequency, the glass wouldn’t break.
Jaime: It’s funny you say that, because I have broken over 20 glasses by voice alone, and it’s just the opposite. I can break the glasses that really resonate (less damped) as opposed to the other glasses. I have broken the damped ones, but I still can’t seem to develop a pattern. Some Glasses, I’ve pulled directly out of the box and unwrapped them, hit the note, and Kaboom! I broke three in a row one day within 10 minutes. Others were a beast to break. I just couldn’t get them resonating really well. I am trying to develop a perfect system for breaking these glasses. I’m only breaking the harder ones by pure determination.
Roger: Well, I separated out 5 well damped, and 5 less damped glasses. That’s not necessarily enough to find a real pattern with. So, I’m not convinced that there’s a pattern. I am definitely convinced that different glasses can be very different. Ha-ha.
Jaime: I’m determined to find a pattern, because I’m still screaming at them. Ha-ha. So what purpose does the hole in front of the speaker serve? Ha-ha.
Roger: I still don’t know. Ha-ha. I can tell you some things that that does NOT help. It makes the sound louder, but we really don’t need it any louder for the glass to break. When we drive that speaker into limiting, we’re hitting 135 dB, and we know that we can break them at 105 dB.
Jaime: So, it’s not the level alone that’s breaking the glasses.
Roger: No, not at all. Some other things that are happening are, the hole is creating constant distortion, it’s creating harmonics.
Jaime: And that’s not a good thing?
Roger: Well, with a signal generator, I can generate a signal that has all of those harmonics, and more, and that signal will not break the glass, even a 135 dB or greater. And it’s not the size of the hole alone. Because the MythBusters brought a 4-inch hole and we could break the glass just as easily as using a 2-inch hole. Meyer Sound makes a 4-inch speaker, so we tested the 4-inch speaker. We could get it close to 105 dB and we knew that you could break them at 105 dB, but we couldn’t get the speaker to break the glass. So it’s something that the hole is doing.
Jaime: I happened to notice something peculiar during practice the day before GMA. When we were practicing, right before the glass would break, the glass would start to be sucked towards the hole as if the hole were serving as a vacuum or creating some magnetic force between the glass and the hole. When I’ve been breaking these with my voice alone, a friend of mine told me that the same thing is occurring. It seems my upper lip is getting pulled towards the glass.
Roger: That’s really interesting. It makes sense that when you put that hole there, that higher order nonlinear acoustic phenomenon are happening. Unfortunately I haven’t had the time to analyze that yet, because it doesn’t make good footage for MythBusters. Ha-ha.
Jaime: On to San Francisco… Were you anxious to see whether I could shatter a glass or not?
Roger: Oh yeah, absolutely. No one has ever seen it before.
Jaime: The one thing I did notice is that I seemed to be blowing them up a lot easier this time around with an amplifier. They seemed to explode within seconds. I’m assuming this is because I have gotten used to zeroing in on the frequencies by practicing at home.
Roger: Yeah I noticed that.
Jaime: Were you surprised when I taught Adam Savage to break a glass?
Roger: Oh Yeah! Absolutely. You do need to get the frequency just right. It was surprising that you were able to help him that fast.
Jaime: But Adam had a good voice, he really does. He was breaking them a lot easier than a lot of the opera singers. It was a rush to see him do so well. I was really proud of him and very happy.
Roger: What I think was happening is, the opera singers would break a glass, then get that pitch stuck in their head. When we’d put another glass up, it wouldn’t be the same pitch, but the singers would keep singing the last pitch and couldn’t find the new frequency.
Jaime: But, Adam broke three!!! He was able to adapt to the frequency. It must be because of my excellent teaching skills. Ha-ha. You know, I’ve broke over 20 glasses by voice alone, and over 50 glasses by amplifier, and I’d bet money on it that very few were the exact same frequency. I’ll find some that are close to the same frequency and line them up. I’d break one and jump right to the next and it just wouldn’t go. But the day I broke 3 in a row by voice alone, none of them were even close to the same frequency. Like you said, they are all so different that you have to focus on each individual glass. When we used an amplifier, did you have to add any certain frequencies to make the glass breaking process easier?
Roger: Yeah. Putting the board in front of the speaker does add some frequencies. But, just the presence of those extra frequencies isn’t enough to break the glass. I can also do that electronically without the board. And, when I did that without the board, it wouldn’t break. So I think there might have to be a particular relationship of the harmonics. There might have to be a certain level compared to the fundamental, Or there might have to be a certain phase relationship between the harmonics and the fundamental. That’s the one theory that I think has promise that, if I have a spare weekend I might eventually test. Especially looking at the glass in slow motion. It would sort of become oval and extend in one direction, and then it would extend in the perpendicular direction, which is what you would expect. But, it didn’t change smoothly from one direction to the next. It would extend in one direction and oscillate there for a while, then, it would extend in the other direction and oscillate there for a while. Just as there are harmonics in the sound, there are spatial harmonics. So that oval shape, that’s the fundamental. Then there are those spatial harmonics going on. That’s those extra oscillations that we are seeing. So, looking at the high-speed footage, I can see the phase relationship between the fundamental and these harmonics. I think that the sound with the board with the hole in it may be causing the harmonics to be having this same relationship to the fundamental. That’s the one last theory I have that I want to test.
Jaime: So, I wonder why you have to use a hole with the speaker, but I can do it with just my voice. I’ve also noticed that sometimes when I break them, I don’t actually have to be that loud. I also know when I’m close to breaking them, because I can feel the sound inside my mouth. It’s like the tone of the glass fills me. It’s like we are two singers singing together. When I can feel that, it doesn’t take a lot of energy or amplitude to break them.
Roger: This is just like the classic example of resonance- a kid swinging on a swing set. If you push them at the same frequency that they are swinging back and forth, the swing will get bigger and bigger. But if the swing is sitting there at a halt and you grab it and shake it really fast, it doesn’t go anywhere, because you are way above the frequency where the swing swings at. And the same thing is going on with you and the glass. If you get in synchrony with the glass, you are pushing and pulling the air in synchrony with the glass. You should be able to feel the glass pushing the air and sound back at you.
Jaime: Do you happen to remember the amplitude and/or frequency at which the un-amplified glass broke?
Roger: It was 105 dB. I don’t remember the exact frequency, but it wasn’t an odd frequency. It was in the 550-570 hertz range. So roughly between Tenor high C and D.
Jaime: At the end of the day, I asked you to check my loudest dB level. How accurate is your dB meter? Because I was actually about a foot back from the tape I needed to stand on for the measurement, and I think I was leaning back when I screamed. You said it was 115 dB. How much would that change if I weren’t in the exact position?
Roger: Maybe 1 or 2 dB.
Jaime: So, we’re talking maybe 117 –118 dB for my top volume? I should’ve screamed a few more times. Ha-ha. The one thing you said to me at the end of the day was that the glasses fatigue. I talked to Jim Gillette about this and he said that they don’t permanently fatigue. You could scream at the same glass 100 times, and it won’t go until it is perfect. So how do you feel about this?
Roger: That’s really a chemistry question and more outside of my expertise. I happen to know a chemistry professor and I asked him about how a glass breaks. He’s the one that told me that glass fatigued. I wouldn’t be surprised if most of the information about fatigue has to do with static stress as opposed to oscillating stress.
Jaime: I figured that as far as fatigue, they probably do, right then and there as I am screaming at them, because, sometimes I’ve had to hold out the note for 10 or 20 seconds. Maybe it’s not that at all. Maybe it’s like the swing analogy, and it just takes a while to build above that oscillation before it will break. Or maybe they fatigue a little bit and they don’t break until I extend beyond that fatigue point.
Roger: I wouldn’t be surprised if you could train yourself to hit that exact frequency faster than the glass fatigues.
Jaime: Do you remember when they brought out that cheaper made wine glass? Of course we knew it wasn’t going to break because it was very damped. Do you remember what the note or pitch of the glass was?
Roger: Yeah, those were another octave higher than the one you broke un-amplified, which was roughly around 550 hertz, or Tenor high C#. The cheap glass was around 1000-1100 hertz.
Jaime: So roughly a Soprano C or C#? You know, I remember when Peter Engle, executive producer of MythBusters made the comment that he knew it wouldn’t break but he was even doubtful that I could hit that high of a pitch. I remember thinking, “wait until he gets a load of me.” Ha-ha.
Roger: Ha-ha. Yeah 523 hertz is the C above middle C, or Tenor high C and 560 is the D. 1026 hertz is the C above that. So it was somewhere between a Soprano B and a C#.
Jaime: That’s still pretty high regardless. I think in New York, I slid up to a Soprano B after I broke the glass on television. And when I am warmed up I can go up to the C above that in whistle voice, but that’s really hard to do.
Roger: Oh wow.
Jaime: Is there anything you’d like to add, or anything about yourself and Meyer Sound?
Roger: I’m very happy that Meyer Sound is very interested in doing this kind of thing. It’s not something that we expect to sell a lot of speakers from necessarily. I think it’s fairly legitimate research. Resonance is something that happens in a lot of systems. It’s not just about selling speakers, it’s also about educating people and how to use something to get the best sound. This is all a part of it, and it’s really great to be a part of this experiment.
Jaime: Earlier you said you wanted to play heavy metal guitar, but I thought you told me you were a bass player?
Roger: I played guitar in high school and listened to a lot of Nitro. In college I switched to bass and I play jazz bass now.
Jaime: It’s so cool that you listened to Nitro, because if it weren’t for you, the MythBusters would never had gotten a hold of Jim Gillette and then he would have never have been able to pass the chance on to me. He is the coolest guy I know!
Roger: I actually bought his instructional tapes in high school. I had a little tape player in the bathroom and I would practice in the shower. It didn’t go any further than that. Ha-ha.
Jaime: Well, I practiced them to, relentlessly. I could sing anything on the Nitro record, but I couldn’t hit the Soprano high D on Freight Train. Of course, now I can, but only in whistle voice. But, nobody wants to hear metal like they used to. I’m 35 and I’m still living in the 80’s. Ha-ha. I even just bought the new Judas Priest CD. Another thing I’d like to mention is that I have been screaming at the round glasses which are higher in pitch. They vary from a D# to an F in the Alto range. The higher I sing, the louder I get. These glasses sing, but don’t break near as easily as the oval glasses.
Roger: I think the shape of the glass matters. The white wine glasses are practically spheres.
Jaime: Yeah, but I think those are the glasses that Jim usually breaks. And that was the first type I ever broke by voice alone.
Roger: I want to add something to an earlier question. The thing to remember about that 115 dB is that that’s 115 dB at 1 meter. If you double that distance, then you subtract 6 dB. And if you cut that distance in half, you add 6 dB.
Jaime: So, if I were at 115 dB at little over a meter, what would you estimate to be the true dB level at which I could scream?
Roger: That’s the thing, because it depends on distance. People who are really serious about measuring dB levels always measure at 1 meter, so that you can compare everyone’s measurement. So other singers might claim higher numbers but you always have to ask at what distance.
Jaime: Well, when I’m screaming into a microphone, that’s not at a meter, and it seems to me, that would be the true measurement at how loud the sound is coming out of me.
Roger: There are things that happen in the near field. Things that happen close to the source that don’t propagate out past a meter or more than a wavelength away from the source. That’s one of the reasons why people are scientific about measuring at a distance. They are only interested in the energy that’s going to propagate away from the source and not the energy that’s circulating around near the source. So you are right. The typical situation for singers on stage is right on the microphone, but I can’t get out of the scientific approach of measuring at a meter. Ha-ha.
Jaime: Well, my thing is, wanting to tell people that I can scream louder than 120 dB. Ha-ha. But I don’t want to lie.
Roger: Oh, I see. Ha-ha. Well, you certainly can, at half a meter.
Jaime: That’s good enough for me. Ha-ha. I’ve been working on increasing volume since New York and my buddy tells me it sound like there is a speaker in my throat. Speaking of which, could you tell a difference in my voice from New York to San Francisco, although we were in a huge theater?
Roger: No, but I was on the other side of the stage.
Jaime: Oh well, where’s breaking glass going to get ya. Maybe 1000’s of kids will buy my book hoping to learn how to break glass with their voice. Ha-ha. Well, I’ve kept you long enough.
Roger: No problem.
Show Related Articles 
