豚鼠对正弦调幅波的频率辨别

当一高频纯音被另一低频正弦波调幅时,从复合声中可听到清楚并占主导的调制波音调。后者随调幅波的频率而变,其辨别阈(△f_(am))可在动物用记录皮层慢反应的方法测定。本工作系统地研究了豚鼠△f_(am)与载波频率、调制波频率、调幅深度、调幅时程、声音强度等的关系。豚鼠对调制波频率似有较好的辨别能力,刺激参数合适时△f_(am)只3—4Hz,与该种动物对纯音的频率辨别阈相近。文中对比了人和豚鼠的△f_(am),并讨论了调制波音调的感受和辩别机理。     

豚鼠对窄带噪声的音调辨别

窄带噪声的调频也和纯音调频一样,能诱发豚鼠的皮层慢反应。反应的阈值(最小调频深度)即可作为对窄带噪声的音调辨别阈(△f)。豚鼠的△f与噪声通带的宽度B及中心频率f有关,△f与B的关系可表达为△f=AB~n。式中A为B=1Hz时的△f值,它与纯音的△f相近并随f而变;在f为1kHz及4kHz时n近似地为1/3。当f在125—8000Hz范围内、B/f比值不变时,△f/f基本上为一常数。这是在频率辨别研究领域内Weber定律的很好示例。△f-f-B三者的总关系在豚鼠可简单地用经验式△f=0.1f~(2/3)B~(1/3)表达。用此式算得的△f值与实验结果相当接近。     

FREQUENCY DISCRIMINATION OF A SINE AMPLITUDE-MODULATOR IN GUINEA PIGS

When a high frequency tone is amplitude-modulated by another sine wave of low frequency,a distinctand predominating pitch corresponding to the frequency of modulating wave can be heard and it changeswhen the frequency of modulator is in turn modulated by a rectangula pulse.Thresholds of frequencydiscrimination of such an amplitude-modulator(f_(am))can be measured in guinea pigs by recording the slowcortical respones evoked by frequency-modulation of the modulator.f_(am)in relation to frequencies of thecarrier and modulator,to the depth of amplitude modulation,to the duration of the rectangular pulse and tosound intensity are systematically studied.The ability of guinea pig for discrimating the modulator seemsrather good.At optimal conditions the f_(am)of guinea pig amounts to 3—4 Hz,quite close to its frequencydifferential thresholds for pure tones.f_(am)in guinea pig and in human(measured by psychophysical method)are compared and mechanism of perception and discrimination of the modulator pitch is disc     

PITCH DISCRIMINATION OF NARROW-BAND NOISE IN GUINEA PIGS

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 f~(2/3)B~(1/3),is proposed,with which the calculated f values are quite close to theexperimentally obtained data.