Based on the assumption that there are three reservoirs of transmitter substance within each hair cell, and the transmitters are released in proportion to the degree of displacement to the basilar membrane, the release is equated with the probability of a spike generated in the nerve fiber.
Assuming that each hair cell contains three stores of neurotransmitter substances, and the amount released corresponds to the extent of displacement along the basilar membrane, this release is likened to the probability of an action potential occurring in the nerve fiber.