Kidd Gerald, Mason Christine R, Arbogast Tanya L
Department of Communication Disorders and Hearing Research Center, Boston University, Massachusetts 02215, USA.
J Acoust Soc Am. 2002 Mar;111(3):1367-76. doi: 10.1121/1.1448342.
This study examined whether increasing the similarity between informational maskers and signals would increase the amount of masking obtained in a nonspeech pattern identification task. The signals were contiguous sequences of pure-tone bursts arranged in six narrow-band spectro-temporal patterns. The informational maskers were sequences of multitone bursts played synchronously with the signal tones. The listener's task was to identify the patterns in a 1-interval 6-alternative forced-choice procedure. Three types of multitone maskers were generated according to different randomization rules. For the least signal-like informational masker, the components in each multitone burst were chosen at random within the frequency range of 200-6500 Hz, excluding a "protected region" around the signal frequencies. For the intermediate masker, the frequency components in the first burst were chosen quasirandomly, but the components in successive bursts were constrained to fall in narrow frequency bands around the frequencies of the components in the initial burst. Within the narrow bands the frequencies were randomized. This masker was considered to be more similar to the signal patterns because it consisted of a set of narrow-band sequences any one of which might be mistaken for a signal pattern. The most signal-like masker was similar to the intermediate masker in that it consisted of a set of synchronously played narrow-band sequences, but the variation in frequency within each sequence was sinusoidal, completing roughly one period in a sequence. This masker consisted of discernible patterns but not patterns that were part of the set of signals. In addition, masking produced by Gaussian noise bursts--thought to produce primarily peripherally based "energetic masking"--was measured and compared to the informational masking results. For the three informational maskers, more masking was produced by the maskers comprised of narrow-band sequences than for the masker in which the frequencies were not constrained to narrow bands. Also, the slopes of the performance-level functions for the three informational maskers were much shallower than for the Gaussian noise masker or for no masker. The findings provided qualified support for the hypothesis that increasing the similarity between signals and maskers, or parts of the maskers, causes greater informational masking. However, it is also possible that the greater masking was a consequence of increasing the number of perceptual "streams" that had to be evaluated by the listener.
本研究考察了增加信息掩蔽声与信号之间的相似度是否会增加非语音模式识别任务中的掩蔽量。信号是由纯音脉冲组成的连续序列，排列成六种窄带频谱-时间模式。信息掩蔽声是与信号音同步播放的多音脉冲序列。听者的任务是在1区间6选1的强制选择程序中识别这些模式。根据不同的随机化规则生成了三种类型的多音掩蔽声。对于最不像信号的信息掩蔽声，每个多音脉冲中的成分在200 - 6500 Hz频率范围内随机选择，但信号频率周围的“保护区”除外。对于中间掩蔽声，第一个脉冲中的频率成分是准随机选择的，但后续脉冲中的成分被限制在初始脉冲中成分频率周围的窄频带内。在窄频带内，频率是随机的。这种掩蔽声被认为与信号模式更相似，因为它由一组窄带序列组成，其中任何一个都可能被误认为是信号模式。最像信号的掩蔽声与中间掩蔽声相似，因为它也由一组同步播放的窄带序列组成，但每个序列内的频率变化是正弦的，在一个序列中大致完成一个周期。这种掩蔽声由可辨别的模式组成，但不是信号集合中的模式。此外，还测量了由高斯噪声脉冲产生的掩蔽（被认为主要产生基于外周的“能量掩蔽”），并与信息掩蔽结果进行了比较。对于三种信息掩蔽声，由窄带序列组成的掩蔽声产生的掩蔽比频率不受窄带限制的掩蔽声更多。此外，三种信息掩蔽声的性能水平函数的斜率比高斯噪声掩蔽声或无掩蔽声的斜率要平缓得多。这些发现为信号与掩蔽声或掩蔽声的部分之间的相似度增加会导致更大的信息掩蔽这一假设提供了有限的支持。然而，更大的掩蔽也有可能是由于听者必须评估的感知“流”的数量增加所致。
