  The Wentzel-Kramers-Brillouin (WKB) approximation is frequently used to
explore the mechanics of the cochlea. As opposed to numerical strategies, the
WKB approximation facilitates analysis of model results through interpretable
closed-form equations, and can be implemented with relative ease. As a result,
it has maintained relevance in the study of cochlear mechanics for half of a
century. Over this time, it has been used to study a variety of phenomena
including the limits of frequency tuning, active displacement amplification
within the organ of Corti, feedforward mechanisms in the cochlea, and
otoacoustic emissions. Despite this ubiquity, it is challenging to find
rigorous exposition of the WKB approximation's formulation, derivation and
implementation in cochlear mechanics literature. In this tutorial, I discuss
the foundations of the WKB approximation in application to models of cochlear
macromechanics in 1-D and 2-D. This includes mathematical background, rigorous
derivation and details of its implementation in software.
