6

Are we hearing a subharmonic? Friends and I hear a note that is lower than my lowest unfretted string on my standard acoustic guitar with standard tuning when I use the following very simple, easy method, pictured here: enter image description here

As seen in the picture, a guitar pick is placed on top of the bass E string and under the next string (A string) in a manner similar to the way folks usually store a pick near the top of the fingerboard. I wedge the pick in between the E and A strings so that the edge of the pick rests on the fingerboard and the A string pushes down on the pick. The pick pushes down on the E string in this manner. (If the guitar action is too high to get the wedge affect, a piece of light cardboard can be placed under the edge of the pick that contacts the fingerboard, in order to shim it.) Then the E string is gently stroked or plucked with my finger. We hear a very low note that is much lower than the E unfretted string would make.

The resultant note is constant frequency, with unremarkable amplitude falloff in a fraction of a second or so. It does not warble or "beat", as far as we can tell. It sounds an octave or so lower than the bass E string.

I am wondering and investigating if it is the brain filling in the "missing fundamental," which is a known phenomenon of human hearing. I cannot find an example of a mechanical system that will produce subharmonics.

  • 3
    Does it matter exactly where the pick goes? – Tim Jan 14 at 8:15
  • 3
    Would be useful to have video or audio of this. – Doktor Mayhem Jan 14 at 9:38
  • 1
    This seems like a dup or related to a question asked last year about sub harmonics. – ggcg Jan 14 at 15:05
  • 2
    And I agree that you need to put audio up. You are asking us all to speculate and guess. You could be hearing things and we would need to hear the same thing. – ggcg Jan 14 at 15:06
  • 1
    Is in on the 19th or 20th fret? Or alternately, how many frets are on that guitar? – luser droog Jan 14 at 19:51
2

The actual tone you hear is lower, because the pick adds mass to the strings. When wedged as shown in the picture, the pick and two strings vibrate together. The frequency is determined by the tension and mass of the strings, the mass of the pick and additional rotational inertia because the pick rotates around its contact point with the fretboard.

On my electric guitar I get almost exact octave drop with a one millimeter Ultex pick, lighter picks produce smaller changes.

Regarding the point about half node presented in the other answer, I believe the pick stays connected to the fretboard and strings all the time. If you pluck the string hard enough that the pick loses contact with one of the parts, you get a buzzing sound not unlike fret buzz and the pick does not stay in place.

Edit: I had a guitar and audio interface at hand, so I had to see what really happens. It turned out that the base frequency drops from E2 to D#2, but with that special pick the first harmonic is much reduced, which makes the usually weak base frequency more audible. This was with the pick at 16th fret, with the pick at 12th fret the pick stops the base frequency and 1st harmonic is stronger.

1

Based on the answers to my question about subharmonics, I think yes, this is a subharmonic. As ojs's answer suggests, you are creating a compound vibrating system out of the two strings and the pick. (Do be scared, so far this is just fancy words describing everything that's already been said)

Think about the whipping around of a string or rope or hose that you've played with in childhood. Now slow down the movie. Sometimes parts of the string are moving up while other parts are moving down and always with some amount of spin around the axis.

The pick wedged against the string creates an artificial node in the string's vibration, but also in a way it's making only half a node because the string can lift off the pick a tiny amount since there is no obstruction in that direction.

The pick absorbs some energy from the pressure and impact of the first string and sets about vibrating, too.

Some of the vibration from the pick is sympathetically transferred to the second string, giving rise to a resonant vibration.

The two (or three) different parts vibrating can easily give rise to the intermodulation effect where difference pitches (aka Tartini tones) are observed.

But I think, sadly the real conundrum for most guitar players will be: "If my pick is wedged in like that, how on earth am I gonna pick the string?" :)

  • I am new to this forum and format. I do not see how to include a recording, and could use some help with that. – Rob Rhamy Jan 15 at 21:13
  • Thanks for the enthusiastic and thoughtful responses. To answer a few things: The – Rob Rhamy Jan 15 at 21:14
  • The fret used was the 19th fret. Interestingly if the 15th fret is used, a higher frequency note is sounded. (Normally, this would result in a lower frequency note.) I read luser droog's answer, and still have some questions in mind. For example, the note I hear is the loudest note. If it is a beat frequency, i would expepct to hear the two notes that form the beat to be present and louder than the beat. – Rob Rhamy Jan 15 at 21:21
  • Also, thanks for mentioning the Tartini tones. I read that part of your answer to my gf, and she started giggling, only stopping long enough to mention things like Tonya's Tortellini TTorts and other more clever deviations. I looked up Tartini tones in an excellent book called "Why You Hear What You Hear" by Heller. It's excellent, but above my understanding of acoustics. – Rob Rhamy Jan 15 at 21:59
  • 1
    Tartini and Paganini both played the violini. I learned the name Tartini from an excellent youtube video by Adam Neely. I know you can add youtube and soundcloud links to posts, but I don't know how to embed them nicely. I'm sure there's a way by following the help links. – luser droog Jan 16 at 3:05

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.