Question

When hit by a sound wave, hair cells in the ear, after an initial, transient motion, settle down to a steady oscillation. The amplitude, A, of this oscillation depends on the frequency of the sound wave, f, measured in hertz (Hz). The figure on the right shows the amplitude of the response of two different hairs (solid and dotted curves) to sounds of different frequencies. Suppose the hair cells are each connected to different neurons which start spiking if the amplitude of oscillation rises above 6 (i) Which neuron is more selective in terms of frequency? (ii) Describe the frequencies a hearing system made of these two neurons could distinguish, justifying your answer. (iii) Briefly describe how this system is similar to Fourier decomposition of sound signals.

Answer 1

(i) The neuron with solid curve is more sensitive in term of frequency.

(ii) The minimum frequecy distinguished by hairing system = 1.4-1.1 = 0.3 Hz

(iii)

0.1tAmplitud 0.01 0.001 0.0001 1E-5 1E-6 1E-7 Frequency (Hz TE-0 110 220 330 440 550 660

The above figure shows the Fourier transform of bass guitar time signal of open string.

It is similar to the graph shown in the question.