Final answer:
The mechanical response of the cochlea is attributed to the gradient in mass and stiffness of the basilar membrane, which allows different regions of the membrane to vibrate at different frequencies of sound waves conducted through the cochlear fluid.
Step-by-step explanation:
The mechanical response of the cochlea is attributed to the gradient in mass and stiffness of the basilar membrane. The basilar membrane changes in thickness, tautness, and width along its length. This variation allows different regions of the membrane to vibrate at different frequencies of sound waves conducted through the cochlear fluid. The gradient in mass and stiffness of the basilar membrane enables the detection of different pitches at different locations along the cochlea.