Did you know that you can estimate the movement of the eyes and the position of the target that the eyes are going to look at just from recordings made with a microphone in the ear canal?
Audiologists are familiar with this technique of recording in the ear canal—we do it routinely with otoacoustic emissions (OAEs). However, Duke University researchers are doing it for a different purpose not related to hearing sensitivity.
In 2018, Gruters and colleagues discovered that when the eyes move, the ears generate a tiny sound, and the other way around. Recently, these researchers conducted another study and demonstrated how these tiny sounds reveal where your eyes are looking (Lovich et al, 2023). By knowing where someone is looking, the Duke researchers were able to predict what the waveform of the subtle ear sound would look like (Lovich et al, 2023)!
Sixteen subjects with normal vision and hearing were asked to visually track a green dot on a computer screen. This task also may sound familiar to audiologists! The dot would disappear and then reappeared either up, down, left, right, or diagonally from its initial location. The sounds from each subject’s ears were recorded in the ear canal as the dot was visually tracked horizontally, vertically, or diagonally.
The eye movements and sounds produced in the ear were analyzed, and results suggested that the eye movements corresponded to specific sounds generated in the ear canal. As a result, the researchers were able to determine which way the eyes were moving based on the recorded sound.
What the researchers don’t know is the exact purpose of the generated ear sounds, but they theorize it has to do with sharpening location skills and space perception. Future projects will focus on how the eye-movement ear sounds may be different in people with hearing or vision loss. The team predicts that, in those individuals, the ear signals will be different, which may affect their localization skills. The researchers also hope that by studying the generator sites of these sounds, newer clinical tests of hearing may be developed.
Gruters KG, Murphy DLK, Jenson CD, Smith DW, Shera CA, Groh JM. (2018) The eardrums move when the eyes move: a multisensory effect on the mechanics of hearing. Proc Natl Acad Sci 115:E1309–E1318.
Lovich SN, King CD, Murphy DL, Groh JM. (2023) Parametric information about eye movements is sent to the ears. Proc Nat Acad Sci 120(48).
Vahaba D. (2023) Your eyes talk to your ears. Scientists know what they’re saying. Duke Today (accessed January 2, 2024).
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