Gockel H, Moore B C, Carlyon R P
MRC Cognition and Brain Sciences Unit, Cambridge, England, UK.
J Acoust Soc Am. 2001 Feb;109(2):701-12. doi: 10.1121/1.1342073.
The mechanism(s) determining pitch may assign less weight to portions of a sound where the frequency is changing rapidly. The present experiments explored the possible effect of this on the overall pitch of frequency-modulated sounds. Pitch matches were obtained between an adjustable unmodulated sinusoid and a sinusoidal carrier that was frequency modulated using a highly asymmetric function with the form of a repeating U or inverted U shaped function. The amplitude was constant during the 400-ms presentation time of each stimulus, except for 10-ms raised-cosine onset and offset ramps. In experiment 1, the carrier level was 50 dB SPL and the geometric mean of the instantaneous frequency of the modulated carrier, fc, was either 0.5, 1, 2, or 8 kHz. The modulation rate (fm) was 5, 10, or 20 Hz. The overall depth (maximum to minimum) of the FM was 8% of fc. For all carrier frequencies, the matched frequency was shifted away from the mean carrier frequency, downwards for the U shaped function stimuli and upwards for the repeated inverted U shaped function stimuli. The shift was typically slightly greater than 1% of fc, and did not vary markedly with fc. The effect of fm was small, but there was a trend for the shifts to decrease with increasing fm for fc = 0.5 kHz and to increase with increasing fm for fc = 2 kHz. In experiment 2, the carrier level was reduced to 20 dB SL and matches were obtained only for fc = 2 kHz. Shifts in matched frequency of about 1% were still observed, but the trend for the shifts to increase with increasing fm no longer occurred. In experiment 3, matches were obtained for a 4-kHz carrier at 50 dB SPL. Shifts of about 1% again occurred, which did not vary markedly with fm. The shifts in matched frequency observed in all three experiments are not predicted by models based on the amplitude- or intensity-weighted average of instantaneous frequency (EWAIF or IWAIF). The shifts (and the pitch shifts observed earlier for two-tone complexes and for stimuli with simultaneous AM and FM) are consistent with a model based on the assumption that the overall pitch of a frequency-modulated sound is determined from a weighted average of period estimates, with the weight attached to a given estimate being inversely related to the short-term rate of change of period and directly related to a compressive function of the amplitude.
决定音高的机制可能会减少对声音中频率快速变化部分的权重。本实验探讨了这一点对调频声音整体音高的可能影响。在一个可调的未调制正弦波与一个使用高度不对称函数（呈重复的U形或倒U形函数形式）进行频率调制的正弦载波之间获得音高匹配。在每个刺激的400毫秒呈现时间内，振幅保持恒定，除了10毫秒的升余弦起始和偏移斜坡。在实验1中，载波电平为50 dB SPL，调制载波的瞬时频率的几何平均值fc为0.5、1、2或8 kHz。调制率（fm）为5、10或20 Hz。调频的整体深度（最大值到最小值）为fc的8%。对于所有载波频率，匹配频率偏离平均载波频率，对于U形函数刺激向下偏移，对于重复的倒U形函数刺激向上偏移。该偏移通常略大于fc的1%，并且不会随fc显著变化。fm的影响较小，但对于fc = 0.5 kHz，偏移有随着fm增加而减小的趋势，对于fc = 2 kHz，偏移有随着fm增加而增加的趋势。在实验2中，载波电平降低到20 dB SL，仅在fc = 2 kHz时获得匹配。仍然观察到匹配频率有大约1%的偏移，但偏移随着fm增加而增加的趋势不再出现。在实验3中，对于50 dB SPL的4 kHz载波获得匹配。再次出现大约1%的偏移，并且不会随fm显著变化。在所有三个实验中观察到的匹配频率偏移无法由基于瞬时频率的幅度或强度加权平均值的模型（EWAIF或IWAIF）预测。这些偏移（以及早期在双音复合体和同时具有调幅和调频的刺激中观察到的音高偏移）与一个基于以下假设的模型一致：调频声音的整体音高由周期估计的加权平均值确定，赋予给定估计的权重与周期的短期变化率成反比，并且与幅度的压缩函数成正比。
