with a combination of voltage-gated calcium channels and calcium sensitive k+ channels, the cells set up an oscillation in voltage and oscillate in response to a depolarizing stimulus. ca enters the cell and depolarizes it, opening k channels which allow k to leave and hyperpolarize the cell. since the exit of k from the cell is delayed, the voltage increases, but then with the exit of the k the cell overshoots the membrane potential and hyperpolarizes. different cells have different delays for k leaving and thus the voltage oscillates at different frequencies. the delays can be as short as 0.7 ms or as long as 150 ms, whereas the ca entry always occurs within about 1 ms (fettiplace, 1987). thus by varying the length of delay for k to leave, cells' ion concentrations can oscillate at specific frequencies. cells with higher oscillating frequencies respond best to higher-frequency sounds, while those with lower frequencies respond best to lower frequency ones. which cells resonate best with a given sound tells the brain what the frequency of the sound is. hair cells that respond to high frequency stimuli send information to specific neurons, and the information remains segregated in the brain. thus, information about sound frequency is preserved, rather than being lost as it would if all information from different hair cells converged on the same neuron or group of neurons.