Fig. 8. Comparison of the predictions for a noise-signal rate-intensity function with the actual measurement.A, Predicted and measured rate-intensity functions. Thesquares connected by the dotted line depict a rate-intensity function for a 4 kHz tone measured for one receptor cell. Using the energy hypothesis and the measured filter constants Cn, a prediction for the rate-intensity function of a noise signal (bandpass filtered between 5 and 10 kHz) is derived (solid line). It is obtained by shifting the pure-tone rate-intensity function by an intensity ΔIEH = 12.1 dB as indicated by thearrow. The measured firing rate of the receptor cell in response to the noise signal is shown by the circles. Data and model prediction agree well in both the overall shape of the rate-intensity function and the location on the intensity axis. The true shift between the measured rate-intensity function is estimated as ΔItrue = 12.6 dB. B, Determination of filter constants. The filled circles depict the measured intensities for pure tones between 4 and 10 kHz that led to a firing rate of 260 Hz in each case. These data were used to determine the filter constants Cn for the 4 kHz pure tone as well as for the range from 5 to 10 kHz. Further filter constants in this range were obtained by linear interpolation of this curve. C, The response function r(JEH) as determined by the rate-intensity function for the 4 kHz tone. The same firing rates that result in the squares in A are plotted against the effective sound intensity JEH of the energy hypothesis. JEH is given by ½ · A2/C2, where A denotes the amplitude of the pure tone and C denotes the filter constant, which is determined by the intensity of the pure tone that drives the cell at 260 Hz. Although the pure-tone rate-intensity function displayed in A has a large nearly linear section from ∼40 to 60 dB SPL, the response function r(JEH) is clearly nonlinear in the corresponding region (from JEH = 0.08 to JEH = 8) and resembles a square-root function. D–G , Predicted and measured rate-intensity functions for the noise signal from four other cells.Symbols are used as in A. Note the different scales on the axes. Accordingly, the slopes of the rate-intensity functions differ considerably from cell to cell, but for a single cell, they are almost identical for pure-tone and noise stimulation. The values for ΔIEH and ΔItrue in these four cases are D, ΔIEH = 9.0 dB, ΔItrue = 9.8 dB, E, ΔIEH = 12.1 dB, ΔItrue = 11.8 dB, F, ΔIEH = 7.8 dB, ΔItrue = 6.6 dB, G, ΔIEH = 14.9 dB, ΔItrue = 18.4 dB.