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Topic: Overtones in non-stringed instruments |
Greg Vincent
From:
Folsom, CA USA
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Posted 19 Jan 2005 8:14 am |
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Hi folks,
Do non-stringed instruments produce overtones in the same manner and series that a string does? For example, does a vibrating column of air vibrate in one piece -creating the fundamental, two pieces -creating the octave, three pieces -creating the octave + fifth, etc?
Does the human voice work that way too?
My buddy's Theramin creates a real pure-sounding tone. Is this instrument creating a note that consists only of the fundamental?
-Insomniac in L.A. [This message was edited by Greg Vincent on 19 January 2005 at 08:14 AM.] |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Posted 19 Jan 2005 8:32 am
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| I believe columns of air do have overtones. That is the way we identify which instrument is playing. I thought theramin was a vitamen. I believe a pure fundamental can be produced electronically, but doubt that any other instrument (including the human voice) does. |
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Earnest Bovine
From:
Los Angeles CA USA
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Posted 19 Jan 2005 8:41 am
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quote:
does a vibrating column of air vibrate in
one piece -creating the fundamental,
two pieces -creating the octave,
three pieces -creating the octave + fifth, etc?
Yes, most air columns can vibrate in one piece (fundamental), or 2,3,4,5 etc pieces. Half the wavelength means twice the frequency. A bugle is a good example, using partials 3,4,5,6.
The geometry of some pipes (called "closed pipes") allows only the odd numbered harmonics. For example, the 2nd register of the clarinet (cylindrical bore) is an octave and a half above the low register. The saxophone is an open pipe due to its conical bore, allowing even and odd partials. So the second register on the sax is an octave above the low register, which is why Bill Clinton can play sax (easy) but not clarinet (hard). Also the reason the clarinet sounds different is mostly because those even partials are not present.
Human voice is more complicated. We can change the tension on our vocal chords and diaphragm, but we can't change the length of our air column. Unchangeable size of air column causes formants; i.e. frequency componenets which are stay the same even tho we sing different notes. This is one way that you can distinguish between different people's voices. |
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Ron Page
From:
Penn Yan, NY USA
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Posted 19 Jan 2005 10:00 am
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Overtones, yes. Cabinet drop, no. 
Great explanation, Earnest! Interesting stuff.
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HagFan
[This message was edited by Ron Page on 19 January 2005 at 10:00 AM.] |
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Greg Vincent
From:
Folsom, CA USA
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Posted 19 Jan 2005 10:13 am
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| Thanks EB! Can a string be made to sound only the odd numbered harmonics --or only the even numenred harmonics? -GV |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Posted 19 Jan 2005 11:03 am
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Wow, the stuff you learn here. EB has finely explained to me why the sax is so much more fun to play than the clarinet - sort of like the difference between C6 and E9. Those even numbered harmonics must make a big difference in sound, and most people like the difference. Electric guitarists always seem to be pleased when their tone is "sax-like." I once read about an experiment where they put some high volume speakers in a pair of rubber underpants that didn't let the sound escape. Basically it produced vibrations in your genitals. They ran different sounds through this apparatus on men and women. Everyone mostly preferred the vibrations of the sex... I mean sax. I have been pleased to play sax ever since.  |
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Earnest Bovine
From:
Los Angeles CA USA
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Posted 19 Jan 2005 12:09 pm
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| Quote: |
| Can a string be made to sound only the odd numbered harmonics --or only the even numenred harmonics? |
Not really, but you have some control over the relative amplitude of the partials, depending on where you pick the string. For example, all even numbered partials have a node in the exact middle of the string. If you pick there, you won't hear much of the even numbered partials.
Don't confuse this with the way people describe smoe classes of vacuum tube amps as emphasizing certain harmonics. That refers to harmonics that are not from your strings, but rather harmonics that are created by distortion in the way that the tube amplifies. |
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Dave Boothroyd
From:
Staffordshire Moorlands
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Posted 20 Jan 2005 5:35 am
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A theremin produces a sine wave, pure sound because what you hear is the difference tone -like the beat between two closely tuned strings- between two oscillators which both run way above audio range. Suppose one is running at 40kHz, and the other one is at 4.4kHz- you will not hear any of the output from the oscillators, but you will hear the difference between the two- 400Hz.
Since all the harmonics generated by the oscillators are higher than 40kHz, , only the fundamentals will produce an audible difference tone, so whatever the waveform of the individual oscillators, the difference tone sounds like a pure sine wave.Any harmonic distortion is produced by the amplification stages.
The process of producing difference tones is called heterodyning.
In practice, one oscillator runs at a fixed frequency, while the other varies according to hand position.
Earnest is spot-on on the harmonics of wind instruments- I'll send him his Diploma any time he asks!
Drums and percussion are a whole new can of worms- and if I explained them, you would soon wish you had never asked.
THe human voice produces a wide range of musical and non-musical harmonics, and we are able to control, to some extent which ones. We also use the resonant cavities in our mouths to act as filters to emphasize or cut certain frequency ranges. These filter settings are called formants and each one represents a vowel sound.
On the same note sing "OOH AAH OOH, AAH" and you will hear and feel the harmonics change- you can go into "Why do Fools Fall in Love?" after that, if you wish!
It is possible to produce an oscillator to produce a signal which is a pure sine wave. A pure sine wave is one fundamental frequecy with no harmonics. Put that signal through an amplifier and it might not be quite so pure. The most obvious thing is that if you turn the gain too high, the signal might go higher than the supply voltage and clip the tops off the sine curve- that adds a lot of harmonics. Maybe inductors and capacitors in the amp will alter the rise and fall time of the signal, and distort its phase. The effort of moving the speaker cone , or ripples in the cone material might add more distortion and thus harmonics.
If you measure the final output, and compare it to the true input you have a figure for "total harmonic distortion" A good amp and speaker rig should manage less that 1% THD.
Oh yes, your ears can add harmonics too! Tinnitus anyone?
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Cheers!
Dave
[This message was edited by Dave Boothroyd on 20 January 2005 at 05:39 AM.] [This message was edited by Dave Boothroyd on 20 January 2005 at 07:16 AM.] [This message was edited by Dave Boothroyd on 20 January 2005 at 07:30 AM.] |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 20 Jan 2005 6:19 am
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Yes, all musical instruments produce overtones, that's what gives each instrument it's particular timbre. Even brass and woodwinds. That's why the same note sounds a lottle different on each instrument.
Even cymbals are full of overtones. Put your ear next to one, and tap it lightly! You'll hear dozens of overtones. |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Posted 20 Jan 2005 6:29 am
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| Suppose one synthetically produces an electronic signal with only the fundamental. Doesn't that have to go through some sort of speaker before we can hear it? Would the speaker add overtones? Is it really possible to produce and actual sound we can hear with no overtones? |
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