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Old 10-12-2011, 12:34 PM
acmeseed acmeseed is offline
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Default Definition of overtones

Hello,

Could you give me a rough definition of what are overtones? Is sustain part of the equation?

I am sorry if this is a dumb question, I have read the definitions on other web sites, but I am looking for the layman's explanation.

Thanks in advance for your feedback.
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Old 10-12-2011, 12:44 PM
Buck62 Buck62 is offline
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Here's a full explaination...

http://en.wikipedia.org/wiki/Overtone


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Old 10-12-2011, 12:47 PM
Ted @ LA Guitar Sales Ted @ LA Guitar Sales is offline
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Here's a full explaination...

http://en.wikipedia.org/wiki/Overtone


.
Ouch, reading that article gave me a headache.
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Old 10-12-2011, 12:52 PM
Alan Carruth Alan Carruth is offline
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We usually think of a string as sounding at one 'fundamental' pitch: A=110 Hz (cycles per second), for example. Really, though, a string can vibrate at quite a large number of frequencies, all at the same time, and usually does. 'Ideal' strings, the kind that only exist in physics books, vibrate in frequencies that are exact multiples of the fundamental, so the A string would vibrate not only at 110 Hz, but 220, 330, 440, 550, and so on. When the frequencies are exact multiples like that (and _only_ then), they're called 'harmonics'.

Real strings don't do that. For one thing, real strings have some stiffness, and that shifts the frequencies of the higher vibrations upward in pitch a little from where they 'should' be. Since they're not behaving themselves and being really 'harmonious', we call those higher pitches above the fundamental 'overtones'.

It's easy to hear these, of course. The fundamental has the whole length of the string moving in the same direction at any one time, and the overtones break it up into shorter sections. Touching the string at the 12th fret divides it into two equal lengths, and sounds the first overtone above the fundamental, roughly an octave higher in pitch (near 220 on the A string). Touching at the 7th fret splits the string length into thirds, and you get the second overtone above the fundamental, a 12th (octave plus a fifth higher) at around 330 Hz, and so on.

Another way that you'll often see these things refered to is as 'partials': the fundamental is the 'first partial', the octave overtone is the 'second partial' and so on.

Any time you play a string there will be some energy in the overtones, but how much will depend on where you play the string. If you pluck it right over the 12th fret, you're telling the string to move at a point where the octave overtone 'wants' it to be still, so there won't be much energy in that overtone. In fact, there won't be much energy in any of the 'even order partials', the ones that are even multiples of the fundamental frequency. That's why the string sounds the way it does when you pluck it there.

Generally speaking, the closer to the end you pluck, the more energy there will be in higher overtones, and the less in the fundamental. That extra high frequency energy accounts for the 'bright' and 'cutting' sound when you play close to the bridge.

Then there's the whole issue of what the guitar _does_ with that energy, but we'll leave that for another post...
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Old 10-12-2011, 12:53 PM
GibbyPrague GibbyPrague is offline
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Old 10-12-2011, 01:02 PM
Glennwillow Glennwillow is offline
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Quote:
Originally Posted by Buck62 View Post
Here's a full explaination...

http://en.wikipedia.org/wiki/Overtone


.
Actually, from my viewpoint, that was a pretty good article. It's a good day for me, Ted -- no headaches.

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Old 10-12-2011, 01:06 PM
Glennwillow Glennwillow is offline
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Quote:
Originally Posted by Alan Carruth View Post
...Really, though, a string can vibrate at quite a large number of frequencies, all at the same time, and usually does. ... real strings have some stiffness, and that shifts the frequencies of the higher vibrations upward in pitch a little from where they 'should' be. ...
Great stuff! You can actually see this effect of a string going slightly sharp after the initial attack with a good clamp-on digital tuner.

- Glenn
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Old 10-12-2011, 01:16 PM
acmeseed acmeseed is offline
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Thanks for the quick responses.

I guess my next question is, are they desirable or not?

My main reason for posting the original question is that when I play my new 814ce with other people plugged in and I strum hard, I can hear the low strings quite loud the sound is almost pleasant, but if I go overboard it starts becoming unpleasant. Last night I was strumming the guitar hard unplugged at home and at one point in time it started sounding unpleasant and I am wondering if that is what some people call the overtones of rosewood.

By the way I love the guitar and that one is staying with me for life, I love the way it sounds, the above is more of a quest for learning to play the instrument the right way, it is in no way a criticism of the guitar.

Thanks.
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Old 10-12-2011, 01:18 PM
pitner pitner is offline
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A Goodall.
I must agree.
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Old 10-12-2011, 01:27 PM
bluesbassdad bluesbassdad is offline
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Alan, please check my understanding of terminology here.

If I touch the string at the 12th fret and pluck it, isn't the resulting sound the second (even) harmonic? IOW isn't what you call the "first overtone" the second harmonic? Is the definition of "overtone" different than that of "harmonic"?

One other nit to pick: When the fundamental is suppressed, as described, isn't the resulting sound actually the sum of the second harmonic and all of the higher, even numbered harmonics, not just the second harmonic?
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Old 10-12-2011, 01:28 PM
Jeff M Jeff M is offline
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Prior forum discussion;

http://69.41.173.82/forums/showthread.php?t=100982
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Old 10-12-2011, 01:29 PM
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patticake patticake is offline
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they can be very desirable or not, depending on individual preference and the use that particular guitar will have. for example, overtones aren't always so good if you'll be playing leads, but can add a really beautiful sound for some fingerpicking.

btw, i've never found that overtones are unpleasant at any time. sounds like maybe you overdrove (is that even a word?) your guitar.

Quote:
Originally Posted by acmeseed View Post
Thanks for the quick responses.

I guess my next question is, are they desirable or not?

My main reason for posting the original question is that when I play my new 814ce with other people plugged in and I strum hard, I can hear the low strings quite loud the sound is almost pleasant, but if I go overboard it starts becoming unpleasant. Last night I was strumming the guitar hard unplugged at home and at one point in time it started sounding unpleasant and I am wondering if that is what some people call the overtones of rosewood.

By the way I love the guitar and that one is staying with me for life, I love the way it sounds, the above is more of a quest for learning to play the instrument the right way, it is in no way a criticism of the guitar.

Thanks.
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Old 10-12-2011, 01:33 PM
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devellis devellis is offline
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Quote:
Originally Posted by acmeseed View Post
Thanks for the quick responses.

I guess my next question is, are they desirable or not?

My main reason for posting the original question is that when I play my new 814ce with other people plugged in and I strum hard, I can hear the low strings quite loud the sound is almost pleasant, but if I go overboard it starts becoming unpleasant. Last night I was strumming the guitar hard unplugged at home and at one point in time it started sounding unpleasant and I am wondering if that is what some people call the overtones of rosewood.

By the way I love the guitar and that one is staying with me for life, I love the way it sounds, the above is more of a quest for learning to play the instrument the right way, it is in no way a criticism of the guitar.

Thanks.
Hard to know from afar, but what you might be describing is the distortion that can occur when you over-drive the guitar's top (i.e., play too hard for that particular guitar). If you've seen people talking about a guitar's "headroom," that's what they're talking about -- the capacity of a top to be driven hard without the sound becoming distorted and unpleasant.

Although this is a sweeping generalization that shouldn't be taken too literally, top woods like cedar or redwood have less headroom than spruces. Among the types of spruce, Engelmann will often have less headroom while red (Adirondack) spruce has more. Again, it depends on each individual piece of wood but that's the general tendency on average. Redwood, cedar and Engelmann are still great woods and they can respond especially well to light input. But headroom isn't their primary strength and they may distort if played too hard (again, not always; just talking about the average tendencies of woods here). Sitka and European spruces often seem to be balanced, responding fairly well to light input and having fairly high headroom.
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Old 10-12-2011, 01:43 PM
bluesbassdad bluesbassdad is offline
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Quote:
Originally Posted by acmeseed View Post
Thanks for the quick responses.

I guess my next question is, are they desirable or not?

My main reason for posting the original question is that when I play my new 814ce with other people plugged in and I strum hard, I can hear the low strings quite loud the sound is almost pleasant, but if I go overboard it starts becoming unpleasant. Last night I was strumming the guitar hard unplugged at home and at one point in time it started sounding unpleasant and I am wondering if that is what some people call the overtones of rosewood.

By the way I love the guitar and that one is staying with me for life, I love the way it sounds, the above is more of a quest for learning to play the instrument the right way, it is in no way a criticism of the guitar.

Thanks.
If you listen to the sound clip in the Wiki article, you may gain some insight: specifically that overtones as a group are neither good nor bad. The first few in the series sound nice in relation to each other (to my ear), whereas the last few don't sound so nice together.

The total absence of overtones would sound very boring to most of us. Listen to the sine wave (a tone that consists of a single, fundamental frequency, 440 Hz in this instance, with no overtones) at the following site:

http://www.hark.com/clips/ytxtclfjjg...onds-12db-loop
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Old 10-12-2011, 01:53 PM
bluesbassdad bluesbassdad is offline
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PC's mention of overdriving the top reminds me of another point, which I hope someone can state more clearly than I'm about to.

So far we've been discussing what I'll call predictable harmonics, for want of a better term.

However, long ago in engineering school I [barely] learned how to analyze the effects of distortion, for example a sine wave with the bottom and the top clipped or rendered flat rather than curved (when represented as a graph of amplitude versus time). It turns out that any periodic waveform, no matter how un-sine wave, can be mathematically represented as a series of sine waves, all of which are harmonics of the fundamental, of various amplitudes.

If one plucks a guitar string hard enough, I presume that the above effect takes place. If so, it would be an instance where overtones, at least some of them, cause the sound to be unpleasant to our ears.

I just now found some more frequency synthesis magic:

http://www.rhythmcreation.com/2007/1...sawtooth-waves

The sine wave consists solely of the fundamental frequency. The other three are combinations of the fundamental plus harmonics or overtones.
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Last edited by bluesbassdad; 10-12-2011 at 02:03 PM. Reason: magic
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