Inner-ear mystery solved

20 March 2006

Why is the cochlea in our ears shaped like a spiral? According to new work by scientists in the US, the spiral shape makes us more sensitive to low frequency sounds.

Daphne Manoussaki of Vanderbilt University in Nashville, Tennessee, together with Emilios Dimitriadis and Richard Chadwick at the National Institutes of Health in Bethesda, Maryland, have shown that the spiral shape probably increases hearing sensitivity to low frequency sounds by as much as 20 dBA. (Phys. Rev. Lett. 96 088701).

The cochlea is a small seashell-shaped organ in the inner part of the ear where sound vibrations are converted into nerve impulses. Scientists have long wondered whether the cochlea's coiled-up shape plays an important role in how it processes sound.

The spiral structure may have developed because animals use low-frequency sounds, which travel the furthest of all sound waves, for communication and survival. The US team will now try to confirm its results by comparing cochlea in different mammals.

Source: PhysicsWeb
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