Jun 6 2017

Promoted from the comment stream, because I am a nerd and there’s a strong chance you might be, too.


In the comments for the previous post, “eub” said:

If I may geek on the tone doubling effect, was it a fairly consistent musical interval, or did the interval get smaller for higher pitches? Like a shift of X semitones, or of X Hertz? There is an uncommon drug effect that apparently sounds like a frequency shift (not a pitch shift), so harmonic sounds become inharmonic and strange.


As a certified nerd, I’m always ready to geek out!

The second tone was a half-step different from the real tone, and tracked in parallel motion: when the real note went up, the fake one did, too, and the size of the difference didn’t get smaller or larger. I right away (well, after calming down a bit) wondered whether it was related to the harmonic overtone sequence, with some peculiar acoustic physics going on inside my inner ear… but in order to find an overtone half a scale-step away from the fundamental, you actually have to climb way the heck up the overtone sequence to the tippity-top. And then it’s not really a half-step away anymore, is it? It would be a half-step plus a bunch of octaves. But this was not a high tone, it was literally right next to the original note on the scale. Which makes me think it was some sort of neurological artifact, and not reflecting any actual physics.

However, there was another phenomenon that was definitely related to physics.

I was tuning my guitar, using an electronic tuner, as I often do (this one a phone app; I love the 21st century). But I was having some trouble because, apparently, the tuner just wasn’t working. But only on the low E string. Worked fine on the high E, the B, the G, the D, the A — But low E wasn’t working at all; because as I could see, the needle indicating “in tune” was perfectly centered. But the note I was hearing was absolutely obviously not E.

What a strange way for an app to go wrong, I thought. Oh, well, just use the good old-fashioned method, put yer finger on the 5th fret of the E string, match it to the open A.

But they already matched.

But this is not possible. If the A on the fifth fret of the E string matches the A of the open A string, then the E string is correctly tuned.

But the open E did NOT sound like an E. It sounded, when I checked, like a B…

An acoustic guitar string is rich in all sorts of complex overtones. So, of course the B would be in there; it’s the second one you’ll find in the overtone sequence (http://www.bsharp.org/physics/guitar). A perfect fifth.

Which is when I realized that I’d lost the ability to hear the low E note itself, and was only hearing the overtones above it. The lowest and loudest of which was the B.

That is, I had become (temporarily) deaf to that frequency.

A actually went to an online tone-generator (http://www.szynalski.com/tone-generator/) and had it generate tones. The low E (around 165hz  correction: Guitar low E is E2 at 82hz), really was gone. Being only a sine wave, with no overtones, gone was gone: no sound. But as I moved the slider up, the sound faded back in.

This was actually a particularly scary moment. There was a small range of frequencies, including that low E, which no longer existed for me.

TEMPORARILY. This I kept telling myself, and so it turned out to be. I hear that low E fine now.

But at that time: I hit that E string and heard a B. Over and over and over.

For a musician, this is a level of weirdness equal to, say, stepping out of your front door and finding that your front steps don’t actually exist, but instead are a clever trompe l’oile image painted on the pavement; or that somehow you are now in Mexico City, when you weren’t before. The world just does not work that way.

Anyway, as I said: all is well now. Can’t say that enough.


Damn, now I’ve got myself all fidgety.

Oh, look, another fuzzy animal picture from my walk, here to cheer me up!

Yo. Public park, here, pal. You are specifically forbidden to eat me.