5:00pm – 5:45pm: “Fact, fiction and cochlear mechanics”
Professor Jonathan Ashmore FRS [Physiology and UCL Ear Institute]

140 years after development of the first mathematical models of the inner ear, there is still no clear agreement about how the cochlea works. The reasons are primarily experimental: the data about the mechanics of this small, inaccessible and fragile structure are hard to come by. At mammalian acoustic frequencies, that is, up to 100kHz, many of the present measurement technologies become unworkable. There are several evolutionary designs of hearing organ but mammalian hearing uses physiologically enhanced mechanics as a means to analyse the frequency spectrum of the incoming sound. The field is at present arguing about the origins of power input into the mechanics. I shall discuss some of the experimental data which constrains mathematical models of cochlear function and some of the classes of model which have been proposed to synthesise the experimental results.

5:45pm – 6:15pm: Break for Refreshments

6:15pm – 7:00pm: “Mode conversion in the cochlea?”
Professor Robert MacKay FRS [Mathematical Interdisciplinary Research, Warwick]

Lighthill argued strongly that the cochlea operates by critical layer resonance (waves of given frequency propagate up to a place where the wavelength and group velocity go to zero and the amplitude rises to a large level determined by a balance between energy flow and damping). There are a number of facts, however, that do not fit easily with this. I propose instead that it operates by mode conversion (waves of given frequency propagate to a place where the group velocity goes to zero but not the wavelength, and then turn round and come back in a different mode). This turns out to be a property of a model proposed by Huxley in 1969. I try to argue how it could arise in more realistic models and how it can make sense of many observations.