Culling J F, Summerfield Q
MRC Institute of Hearing Research, University Park, Nottingham, United Kingdom.
J Acoust Soc Am. 1995 Aug;98(2 Pt 1):837-46. doi: 10.1121/1.413510.
Two experiments investigated the effect of frequency modulation on the identification of vowel sounds presented concurrently with interfering vowels. In experiment 1, identification thresholds were measured for each of five target vowels, masked, in each trial, by one of ten masking vowels. Both target and masking vowels were synthesized using harmonically spaced frequency components. Inharmonic spacing was used in order to prevent powerful grouping processes which exploit fundamental frequency from dominating the results. The target vowels were synthesized with sinusoidal frequency modulation on each frequency component which was either coherent (same phase) or incoherent (random phases). The masking vowels were synthesized with components which were either modulated in the same way as the target vowel or were unmodulated. Identification thresholds were lower when the masking vowel had no modulation. The effect occurred for both coherent and incoherent frequency modulation, indicating that it is mediated by the movement of each component independently, rather than by grouping of coherently modulated components. This result is consistent in some respects with judgments of the prominence of competing vowels [S. E. McAdams, J. Acoust. Soc. Am. 85, 2148-2159 (1989)], which show that modulated vowels are more prominent than unmodulated vowels regardless of the type of modulation applied to the competing vowels. Experiment 2 used a paradigm similar to that developed by McAdams, in order to compare more directly the effect of FM on vowel identification and vowel prominence. On each trial, three vowels were presented concurrently. Either none, one, or two of the vowels were modulated throughout, while modulation was applied to another vowel (the target) halfway through the stimulus. The vowels were either harmonic (with different fundamental frequencies) and coherently modulated or inharmonic and incoherently modulated. Accuracy of identification of the target vowel was not significantly different in the harmonic/coherent and inharmonic/incoherent conditions and declined, in each case, as the number of modulated background vowels increased. Overall, the results of experiments 1 and 2, and of McAdams' prominence judgment data, suggest that there is an auditory mechanism for detecting frequency modulation which can alert the listener to the presence of frequency modulated sounds, but which is insensitive to across-frequency differences in the pattern of that modulation.
两项实验研究了频率调制对与干扰元音同时呈现的元音识别的影响。在实验1中，测量了五个目标元音中每个元音的识别阈值，在每次试验中，由十个掩蔽元音之一进行掩蔽。目标元音和掩蔽元音均使用谐波间隔的频率成分合成。使用非谐波间隔是为了防止利用基频的强大分组过程主导结果。目标元音在每个频率成分上以正弦频率调制合成，调制要么是相干的（同相），要么是非相干的（随机相位）。掩蔽元音的合成成分要么与目标元音以相同方式调制，要么未调制。当掩蔽元音没有调制时，识别阈值较低。这种效应在相干和非相干频率调制中均出现，表明它是由每个成分的独立移动介导的，而不是由相干调制成分的分组介导的。这一结果在某些方面与竞争元音突出性的判断一致[S. E. 麦克亚当斯，《美国声学学会杂志》85, 2148 - 2159 (1989)]，该研究表明，无论对竞争元音应用何种调制类型，调制元音都比未调制元音更突出。实验2使用了与麦克亚当斯开发的范式类似的范式，以便更直接地比较调频对元音识别和元音突出性的影响。在每次试验中，同时呈现三个元音。在整个刺激过程中，要么没有元音、有一个元音或有两个元音被调制，而在刺激过程的中途对另一个元音（目标元音）应用调制。元音要么是谐波的（具有不同的基频）且相干调制，要么是非谐波的且非相干调制。在谐波/相干和非谐波/非相干条件下，目标元音的识别准确率没有显著差异，并且在每种情况下，随着调制背景元音数量的增加而下降。总体而言，实验1和2的结果以及麦克亚当斯的突出性判断数据表明，存在一种用于检测频率调制的听觉机制，该机制可以提醒听众频率调制声音的存在，但对该调制模式中的跨频率差异不敏感。
