＜正＞Frequency modulation of a narrow band noise evokes slow cortical responses（SCR）in guinea pigs just asfrequency modulation of pure tone does.Pitch difference limen of the narrow band noise can thus beeasily obtained by measuring the SCR threshold in terms of modulation depth.In guinea pigs values arefound to be noise hand-width（B） and central frequency（f）dependent and the f-B correlation can beexpressed as f=AB"where A is the key value of ffor a given fat B=1 Hzand,for f’s of 1 kHz and 4 kHz,napproximates to 1/3.The f/f ratio is essentially a constan for all test f’s ranging from 125 Hz to 8 kHz,provided Bis set sccording to a fixed B/frate.This is a very good demonstration of the Weber’s law in respectto pitch discrimintion.For expressing the overall f-f-B relationship in guinea pigs a simple empiricalformula,f=0.1 f2/3B1/3,is proposed,with which the calculated f values are quite close to theexperimentally obtained data.
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