In this talk, I will address two problems that arise in the cochlea during the conversion of a sound into an electrical signal. Although von Helmholtz recognized in the 19th Century that the ear contains an array of resonators like a piano that contains an array of strings tuned to particular frequencies, viscous friction in the liquid that fills the inner ear prohibits any passive resonance. Like the strings of a piano in honey, the ear’s mechanotransduction elements are over-damped and will not resonate unless several conditions are satisfied. I will demonstrate that the balance of the viscous, elastic, and inertial forces in the ear’s mechanotransduction organelle, the hair bundle, minimizes viscous friction and thus makes the sensitive hearing possible. The ear’s solution to this problem reflects general principles of fluid-structure interaction that apply to other biological and non-biological systems at small Reynolds numbers. The second problem is how the ear’s mechanotransduction apparatus operates at the molecular level to transduce and amplify sounds. Classical models of this process have been challenged by experimental results, and the solution to this problem remains a mystery. I will propose a new hypothesis that is based on firmly established principles of interaction between integral proteins and the lipid bilayer. I will discuss how we will test this hypothesis experimentally.