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Acoustic vs Electric Instruments

  1. May 31, 2006 #1
    Where does the sound difference between acoustic and their electric counterparts come from, even when playing the same sustained note (i.e., same frequency)?
     
  2. jcsd
  3. May 31, 2006 #2

    Danger

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    In accoustic instruments, air is manipulated in some manner to provide the sound. A guitar, for example, is a resonating body. The strings set up vibrations which are 'focused' through the instrument. Same for a piano, but on a different scale.
    In an electric guitar, the strings (which you'll note are metal) interrupt the field of a magnet or several magnets in the bridge. A sensor picks that up and pre-amplifies it in the internal circuitry. The amplifier that the guitar is plugged into is actually part of the instrument. Unplugged, an electric guitar makes almost no sound. There are additional circuits specifically designed to introduce certain amounts of distortion, which leads to the unique sound of the electric instrument.
    An electric piano is essentially a synthesizer. Different circuitry is activated according to which keys (switches) are pressed.
    There is a very good article on electric guitars in 'How Stuff Works'. I'll be back shortly with a link.

    edit: Here ya go, dude. http://entertainment.howstuffworks.com/electric-guitar.htm
     
    Last edited: May 31, 2006
  4. May 31, 2006 #3
    Same note different sounds

    What Danger said covers how the sounds are made, as far as how sounds can, well, "sound" different even though they're playing the same note...

    In a word - overtones, or "harmonics".

    This gets a little hard to explain w/o diagrams, but I'll try anyway.

    O.k.

    When an acoustic or electric guitar play a note, any note, they never produce what's called a "pure tone". Which is actually a GOOD thing. "Pure" tones sound VERY "electronic" or artificial. (In fact an electric guitar with no effects or distortion is reasonably close to a "pure" tone).

    When you play a "middle A" on either an acoustic or electric guitar the loudest, or most prominent note you hear, is 440Hz.

    But it's not ALL you're hearing.

    In addition to that, the string produces an entire range of higher frequencies called "harmonics".

    What makes ANY instrument sound unique, even though it's playing the exact same note as any other instrument, is the unique mix of harmonics it produces.

    Electric guitars produce a very different mix of harmonics than acoustic guitars, which is why they sound different even though they're playing the same note.

    In fact that's why a sax sounds like a sax, while a piano sounds like a piano, and a flute sounds like a flute, an oboe like an oboe, etc., even when each of them is playing the same note.

    Each of them produces a different harmonic spectrum which is what gives each type of instrument it's unique and identifiable sound.

    And it actually gets a little more complicated than that. The harmonic spectrum any instrument produces isn't static. It changes from instant to instant as a note is sustained. So how the harmonic spectrum morphs from when a sustained note starts, to when it fades away, also gives each instrument a unique and identifiable character.

    This is actually what makes imitating various instruments fairly complicated when using a synthesizer. It's very easy for a synth to produce a pure tone. It's not even all that hard to produce a particular harmonic spectrum with a synth. What can be near to impossible is duplicating how the harmonic spectrum changes as a note is sustained.

    Which is why sampling synthesizers have become so popular. It's easier to just record the notes produced by an instrument digitally, and then just play them back. (Then again, try playing a ratty trumpet or sax part on a sampling keyboard and you're quickly going to find that "articulation" is WHOLE 'nuther ball of snakes to get lost in).

    Hope this helps!
     
  5. May 31, 2006 #4

    Danger

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    Excellent post, Monsters. I ignored that part of the question because I didn't know the answer. Thanks for the insight.
     
  6. May 31, 2006 #5

    turbo

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    It's even more complex than Monsters' explanation. I have been playing electric guitar for about 40 years and have maintained and /or modified my own guitars and tube amplifiers for most all that time. Amplifiers can color the sound of an electric guitar significantly, and there are people who swear by Fender tweed, brownface, and blackface models of certain circuit types, early Vox and Marshall amps, etc. There is an important truth that many people misunderstand - an electric guitar is not a monolithic machine that simply sends electrical signals to an amp. Every electric guitar is different, even seemingly identical ones, and there are significant tonal differences from model to model. I will not buy an electric guitar without stringing it up with a new set of strings and playing it extensively in a quiet room to listen for its resonance, sweet spots, etc. One guitar may have a rich resonant tone with lots of of overtones, while a seemingly identical guitar in the same shop may be essentially dead!

    The differences are attributable to many characteristics. Perhaps the most iconic rock and roll guitars are the Gibson Les Paul, and the Fender Stratocaster. The LP is rigid and is heavy as all get-out, with a thick mahogany body with a maple cap, and a glued-in mahogany neck with an ebony or rosewood fingerboard. The Strat has a much lighter body and a bolted-on neck with either a full maple neck, or a maple neck capped with a rosewood fingerboard. The string scale of the Strat is longer, and the Strat's bridge "floats" to allow the operation of a spring-compensated tremolo bridge. These guitars sound very different, even if you equip them with similar electronics. That said, a very expensive custom-shop Gibson or Fender may very well be out-done by a standard production model that just happens to have the "right" combination of body wood, neck wood, geometry, etc. I have two wonderful acoustic guitars, and two wonderful electric guitars. Both of the electric guitars would be considered "off" brands by most players who vote with their pride and preconceptions, but they are keepers, and they cost a whole lot less than the "iconic" guitars. BTW, I have owned several dozen electric guitars, including a 1959 Fender Stratocaster and a 1960-vintage Les Paul Custom, so I'm not impressed by price or reputation - just tone.

    You may be interested in the fact that Eric Clapton's long-time favorite Stratocaster "Blackie" was not an off-the-shelf model. He bought a bunch of Strats, and he mixed-and-matched the parts of those Strats until he ended up with what he felt was the most toneful combination, and that became his main recording instrument.
     
    Last edited: May 31, 2006
  7. Jun 1, 2006 #6
    Thanks a lot, this is just the information I needed.
     
  8. Jun 1, 2006 #7

    Mk

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    Ahha! So this is why Paul Gilbert
    I still have no idea what that says, but amplifiers are different now.
     
    Last edited: Jun 1, 2006
  9. Jun 1, 2006 #8

    rcgldr

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    One thing left out of the links and this thread is where you pick or pluck the string of a guitar. If the string is plucked at the middle, it's mostly the primary harmonic, with very little amplitude of the other harmonics. If you pluck the string close to either end, you get higher amplitudes of the other harmonics. Plucking the string where a particular harmonic would peak on the string will produce more amplitude for that harmonic.

    The primary harmonic will always the the dominate sound on an acoustic, non-amplified guitar. With an electic guitar, feedback from a nearby speaker can cause a harmonic overtone to become dominate.

    The weight of the strings and tension (more tension required with heavier strings) also affects the sound quality.
     
  10. Jun 1, 2006 #9
    CScot...

    We might be able to getcha even more useful info if we know why yer askin.
    There are SO many sources, and SO much involved w/this kinda thing, ya know?
    Wadder ya tryin' ta do, or learn?
     
  11. Jun 1, 2006 #10
    Turbo-1

    A fellow mew-zi-shun!

    A '58 Gibson SG, totally stock, right down to the ****ty original whammy bar - through a Marshal JMP-1, (which is a tiny bit less moody than a :) "real Marshal".

    A Dan Armstrong model Ampeg (the clear one w/frets usin' the original "Rock #6 pick-up, and even the original TOTALLY ****ty one piece cast bridge), - through an ANCIENT Ampeg "VT-4" amp (which is one VERY moody bastard) w/matching 4 x 6 cabinet.

    You?
    ----------------------
    Man you are just DEAD RIGHT about guitar/amp combo's bein' key right on down to individual instruments and amps.

    Even the process and equipment used to record music has a HUGE effect.
    Straight digital recording often isn't the way to go for some sounds. It can actually be too accurate. We often ran tracks from a digi straight to hardrive recording, onto a Struder deck runnin' 2 inch Ampex tape, and then bounced the tracks back into the hardrive, all just to get a "warmer sound" to the recording before mastering.

    Neve eq's vs. pretty much anything else, the individual peculiarities of any given recording room, the make model and even at times year of manufacture of the mixing desk routing the audio signals between various recording and effects gear, individual mike choices and placement, what kind of monitors you're using for playback, GEEZE - the position of the Moon according to the solunar tables that day for cryin' out loud! It can all make a differance people can hear.

    Heh. Most of us have also been told that the average human ear can only precieve sound between 20hz and 20khz.

    Ha! 20hz to 20khz my ass.

    Interactions between upper harmonics well above 20khz are definitly perceptable to the human ear. They usually show up as perceived differences in "presence".

    Like you said - this kind of thing gets REALLY complicated. Far more complicated than any explanation in a post could possibly hope to cover.

    The bottom line is that the human ear is absolutely unbelievable at picking up some of the most subtle differences in pretty much any acoustic waveform that almost ANY variance can be detected by a practiced ear.
     
    Last edited: Jun 1, 2006
  12. Jun 1, 2006 #11
    Jeff Reid

    You are absolutely right about THAT one (where you pick a string makes a very real difference).

    Just ONE example of that... Barely touching a string up near the twelfth fret while picking it in the usual spot just over the pick-ups causes the string to vibrate more intensely in two halves, resulting in what musicians call a "harmonic".

    VanHalen and Yes were known for making it a popular technique widely practiced by MANY musicians (once they figured out how their favorite "Rock God" was doing it). ;-)
     
    Last edited: Jun 1, 2006
  13. Jun 1, 2006 #12
    Yet ANOTHER complexity...

    So called "transposing insturments" don't produce waveforms where the fundemental frequency played is the most prominent waveform precieved.

    As a result transposing instruments "sound" like they're playing a different note than they really are. That's why the sheet music for any given song to be played by - say, a piano and a trumpet, will be written in different keys (i.e. "transposed"). They have to be transposed so that both insturments "sound" like they're playing in the same key, even though in reality, they're not.
     
    Last edited: Jun 1, 2006
  14. Jun 2, 2006 #13
    Mk ...

    True, amplifiers ARE different now, but so are the tonal qualities they produce.

    "Distortion" is one INCREDIBLY complex issue.

    "Distortion" is caused by an amp "clipping" the signal it's amplifying. And "clipping" is a pretty good and descriptive term for what's happening to the signal.

    Picture a nice smooth sine wave. It's got no really sharp bends in it.

    "Clipping" happens when the amp tops out in how much it can amplify the signal. As a result the top of the oh so smooth sine wave gets "clipped" off. So now the sine wave is no longer smooth at all. It goes up smooth, but then, before it reaches the top of the curve where it would normally transition from going up to going down in a gentle smooth curve - it *very* suddenly goes dead horizontal, in a straight line, because the amp isn't capable of outputting a higher amplitude signal. That means that the top of the sine wave is literally cut off, which leaves a kind of flat top to the curve as if you cut off the top of the sine wave (or any other otherwise "smooth" wave) with a razor blade.

    Now here's the thing. A pure sine wave HAS no "upper harmonics". None. It's a "pure tone". Which is another way of saying that the signal has no sharp corners to it. It's smooth, and "smooth", as in no sudden changes to the slope of the curve, is analogous to "no upper harmonics".

    A saw tooth wave is just the opposite. It has extremely sharp bends in it, i.e. extremely sharp changes in the slope of the curve, which is another way of saying that it's LOADED with upper harmonics.

    It's the presence of upper harmonics that make for sharp changes in the slope of any curve.

    So by clipping off the top of an otherwise smooth curve, thereby forcing the slope of the curve to change suddenly, you're adding upper harmonics into the signal.

    And THAT is precisely what "distortion" in an amp is DOING to the incoming signal. It's adding upper harmonics to it that weren't there originally, even to parts of the signal that weren't just pure sine waves. Which RADICALLY alters the perceived tonal quality of the signal.

    Now the thing is, that'd be an easy thing to duplicate if all amps clipped off the same frequencies at the same amplitudes, but they don't. Not even CLOSE. Not only do different brand and models of amps clip different frequencies off at different amplitudes, INDIVIDUAL AMPS of the exact same make and model, "clip" at least slightly differently, due to, for example, tiny variations in the length and path of the wiring inside them!

    This kind of over sensitivity is also what makes "tube amps" "moody". As in the very same amp will sound just a tad different, on different days, even though all the settings on the amp are the same. The difference is usually VERY subtle, but trust me, MORE than enough to piss off a musician who KNOWS his amp COULD sound better, just a tiny bit better, if it wasn't in a pissy mood.

    Solid state amps have circuits in 'em that try to mimic the clipping dynamics of popular classic tube amps, but VERY few of 'em come anywhere close to "the real thing" to a trained ear.

    When musicians say that a particular type of distortion sounds more "natural" they generally mean that the distortion sounds "smoother", less "poppy", or "farty" sounding, more velvety. All of which are very metaphorical terms for variances in how the signal is being clipped that would be EXCEPTIONALLY difficult to boil down to more technically sophisticated, not to mention more accurate terms.

    That help?
     
    Last edited: Jun 2, 2006
  15. Jun 2, 2006 #14

    turbo

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    There's more...I have a fondness for power supplies that are "saggy" - in other words the rectifier tube (yes, it HAS to be a tube!) can't supply the instantaneous current demanded by the circuit under load, causing the voltage on the B+ rail to sag, and "brown" the tone and allow the notes to "bloom" as they decay.

    Some of my favorite rigs have been:

    1965 SG standard through an Ampeg Portaflex 2x12 loaded with SROs (college frat-party rig!)

    Heavily customized Epiphone LP tuned to open E for slide through my home-made clone of a Fender 5E3 (tweed Deluxe)

    Yamaha SA800 through my (serial number 2) Carlson Turbo-Pup. 2x10 combo ~35 Watts with EL34s. A wonderful hand-made amp by Mark Norwine, who has become more than an amp-maker to me - a friend. This combination has yielded the best outdoor party tone of any guitar-amp pairing I have used. I was playing for a biker party (with a lot of people who had heard me and my band before) and guys were coming up and saying "Man! what did you do?" "You guys sound great!" etc. It was a blast. Cranking that amp with no effects and a lively semi-hollow body (ES335 clone) was just the trick for outdoors.

    Another good outdoors rig was a "lightly" customized (few of my amps escaped unscathed) '59 Bassman repro and an Ibanez Talman with lipstick pickups. The 2 and 4 selector positions (neck and middle pickups and middle and bridge pickups) just killed, and I was able to nail some great classic rock tones. I used that rig at an employee BBQ for a long-haul trucking company. There were two other bands, and the other guitarists clamored to use this set-up.

    1968 Tele through a similar-vintage Princeton Reverb. Great marriage.

    The aforementioned heavily modded Epiphone LP with warm SD pickups through a fully restored '66 Fender Super Reverb. Great for slide (Elmore James) and for early Cream stuff. I was running NOS output tubes biased pretty hot. I refretted the guitar with Rock Jumbo Dunlop frets, made a new bone nut, and did a few other things.

    Modded Fender Esprit through just about any amp I owned.
     
    Last edited: Jun 2, 2006
  16. Jun 4, 2006 #15
    You guys are pretty intense :tongue:. I've got loads to point out for my presentation now, though. Thanks again.
     
  17. Jun 7, 2006 #16
    Alright, I'm about to write some stuff down so I want to make sure I have this correct. A lot of the "sound" of an instrument, when playing a single sustained note, will come from the range of harmonics produced by that particular string and it's acoustic envelope? (And different harmonics should show on the acoustic when compared to the electric?)

    Fourier Analysis Problem: When playing [itex]A_2[/itex] (110 Hz) on the electric we get 110 Hz and ~175 Hz with a amplitude of 1.0 (FFT) and the rest is under 0.1 amplitude. Could this just be our recording quality or could the 175 just be specific to this instrument? How come there aren't any other harmonics showing up - again, recording qual?

    We are micing the amp.

    EDIT: Wikipedia says that overtones don't have to be integer multiples, so I guess this is ok?
     
    Last edited: Jun 7, 2006
  18. Aug 3, 2010 #17
    hi
    do you have any aidea in designing accoustic encloser in diesel generators.
    pls suggest me any of the sites
     
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