豚鼠对窄带噪声的音调辨别

PITCH DISCRIMINATION OF NARROW BAND NOISE IN GUINEA PIGS

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 modulation of a narrow band noise evokes slow cortical response (SCR) in guinea pigs just as pure tone modulation does. Pitch difference limen (Δf) of the narrow band noise can thus be easily obtained by measuring the SCR threshold in terms of modulation depth. In guinea pigs Δf values are found to be dependent on noise-band width (B) and central frequency (f) and the Δf-B correlation can be expressed as Δf=AB' where A is the key value of A/ for a given f at B = 1Hz and, for f's of 1kHz and 4kHz, n approximates to a simple fraction of 1/3. The Δf/f ratio is essentially a constant for all examined f's ranging from 125 Hz to 8 kHz, provided B is set according to a fixed B/f rate. This is a very good demonstration of the Weber's law in respect to pitch discrimination. For expressing the overall Δf-f-B relationship in guinea pigs, a simple empirical formula, Δf=0.1f2/3B1/3, is proposed with which the calculated Δf values are quite close to the experimentally obtained date.