Monday, January 2, 2012

Ear Canal Resonance Follow-Up

In my previous post about ugly sounds, I made a note about what I thought to be missing information regarding Reuter and Oehler's research:
I lament that there doesn't seem to be a complete, published paper by Reuter et al., at least not yet (but I couldn't wait any longer). I have no way to draw further information from their raw data or even determine how they decided what frequency range qualified as that which the ear is most sensitive to — I assumed they cited some other work, but in my search of all of their cited work, nothing seems to present such research. They presented their work in a 15 minute session at a meeting of the Acoustical Society of America in San Diego on November third.
I emailed Dr. Reuter and he responded promptly with a succinct reminder of my musical acoustics education (edited for clarity):
From a mechanical perspective the outer ear canal works like a tube, which is open at the one end (pinna) and closed at the other end (eardrum). Tubes like this can also be found in musical instruments like organs (the so-called "gedackt" register) and clarinets. One of the main characteristics of these tubes is that their transmission is especially strong at 1/4 wavelength. If you think about the speed of sound (340 m/s) and the length of our ear canal (about 27 mm), then you can calculate the ear canal resonance frequency with the equation f = c/lamba (frequency = speed of sound / wavelength): x = 340m/s / 0,027 m *4 = 3148 Hz as resonance peak.
(Note that the wavelength used is 4 times the given ear canal length, hence the multiplier.)

He even included page-specific citations for this and for some further psychoacoustic research.  While it seems like this is a fairly well-established fact, I still hope he cites the experiments that confirm the range of resonance peaking discussed.

In other news (edited for clarity):
Michael Oehler and I are carrying out further experiments about chalkboard sounds.... The whole study will be published in the middle of the coming year I suppose.
Don't let me forget to look for that.  Also, I could write about how tube-like instruments produce their sound if that part of Reuter's email made you wonder — if you're interested, let me know in the comments.

1 comment:

  1. This is a reminder to look for that article about the chalkboard.