Hearing (with) the Ears

As I mentioned in a previous post, I just participated in a hearing study. The researchers are gathering data about people with tinnitus and hyperacusis, as well as people like me, with regular hearing. Part of the testing they do uses otoacoustic emissions (OAEs).

These are sounds actually made by your ear in response to sounds you hear. From what I understand, measuring these sounds (through a little microphone in the ear canal while playing beeps through a little speaker in your ear) can tell someone how good your hearing is, without requiring you to say “yeah, I hear that.” Because of this, OAES are often used to test hearing in babies. I’m assuming it has something to do with the resonant frequencies of your hearing apparatus, although I’m sure some actual scientist could give a better explanation. If you by any chance are such a scientist, please put a real explanation in the comments!

As you might expect, artists have gotten their hands on this bit of auditory trivia:

Jacob Kirkegaard

Kirkegaard has a work titled “Labyrinthitis,” in which he stimulated OAEs in his own ears (you can hear a sample of the piece on the site but it does not induce the effect in your ears). These sounds, amplified, were then paired to stimulate the ears of the audience. From there,

Stimulated by the distortion that these two tones will create in their own ears, the audience will be able to perceive a third tone. In a next step, Kirkegaard lets the two primary tones disappear and adds the third tone to the composition: It can now be heard “for real”, not just individually, in the room. Once this tone is established, a new tone is added in order to create, in combination with the earlier (third) tone, a further distortion in the same manner as before. By feeding more and more of these pairs of frequencies into the spiral structure of the ears of the audience, Kirkegaard goes on to create a descending tonal structure based on the resonant spectrums of the human cochlea itself.

I have no idea if this is actually what goes on in the ears or just a projection based on the math of OAEs but it is certainly an evocative reflection on the hearing apparatus and the existence of otoacoustic effects.

Great writer on sound art Douglas Kahn wrote an appraisal of the work.

Maryann Amacher

Amacher works with the acoustics of architectural space as a medium, exploring the site-specific qualities of hearing. Some of her work (though to be honest, I am not that familiar with her output) induces OAEs in the audience, when played at loud volumes, effectively making melodies out of these sounds. I assume the “loud volume” part is to make the normally quiet sounds actually audible in your own head. Having experienced the effect, it is a strange and spatializing kind of hearing—depending on how you turn your head and the shape of the room, this buzzing melody seems to move around and change just inside your head.

I’ll post a clip of her work in an audio post after this one.

Two other things

Tartini tones in music are ostensibly related to OAEs (although, like many such musical terms, they work in mysterious ways/might actually be a few different phenomena).

and

Your ears’ response to stimuli designed to provoke OAEs is apparently specific to your own cochleas. Cue creepy futuristic use of OAEs as biometric ID to ensure that only you can listen to your iPod (what?).