Calcus Axelle, Schoof Tim, Rosen Stuart, Shinn-Cunningham Barbara, Souza Pamela
UCL Speech, Hearing and Phonetic Sciences, London, United Kingdom.
Laboratoire des Systèmes Perceptifs, Département d'Etudes Cognitives, Ecole Normale Supérieure, PSL University, CNRS, Paris, France.
Ear Hear. 2020 Jan/Feb;41(1):208-216. doi: 10.1097/AUD.0000000000000741.
This study aimed to evaluate the informational component of speech-on-speech masking. Speech perception in the presence of a competing talker involves not only informational masking (IM) but also a number of masking processes involving interaction of masker and target energy in the auditory periphery. Such peripherally generated masking can be eliminated by presenting the target and masker in opposite ears (dichotically). However, this also reduces IM by providing listeners with lateralization cues that support spatial release from masking (SRM). In tonal sequences, IM can be isolated by rapidly switching the lateralization of dichotic target and masker streams across the ears, presumably producing ambiguous spatial percepts that interfere with SRM. However, it is not clear whether this technique works with speech materials.
Speech reception thresholds (SRTs) were measured in 17 young normal-hearing adults for sentences produced by a female talker in the presence of a competing male talker under three different conditions: diotic (target and masker in both ears), dichotic, and dichotic but switching the target and masker streams across the ears. Because switching rate and signal coherence were expected to influence the amount of IM observed, these two factors varied across conditions. When switches occurred, they were either at word boundaries or periodically (every 116 msec) and either with or without a brief gap (84 msec) at every switch point. In addition, SRTs were measured in a quiet condition to rule out audibility as a limiting factor.
SRTs were poorer for the four switching dichotic conditions than for the nonswitching dichotic condition, but better than for the diotic condition. Periodic switches without gaps resulted in the worst SRTs compared to the other switch conditions, thus maximizing IM.
These findings suggest that periodically switching the target and masker streams across the ears (without gaps) was the most efficient in disrupting SRM. Thus, this approach can be used in experiments that seek a relatively pure measure of IM, and could be readily extended to translational research.
本研究旨在评估言语对言语掩蔽中的信息成分。在存在竞争说话者的情况下的言语感知不仅涉及信息掩蔽（IM），还涉及许多在听觉外周中掩蔽器与目标能量相互作用的掩蔽过程。这种在外周产生的掩蔽可以通过在对侧耳（双耳分听）中呈现目标和掩蔽器来消除。然而，这也通过为听众提供支持掩蔽空间释放（SRM）的定位线索而降低了IM。在音调序列中，IM可以通过快速切换双耳分听目标和掩蔽器流在双耳间的定位来分离，大概会产生干扰SRM的模糊空间感知。然而，尚不清楚该技术是否适用于言语材料。
在17名听力正常的年轻成年人中测量了言语接收阈值（SRT），这些成年人在三种不同条件下收听一名女性说话者的句子，同时存在一名竞争男性说话者：双耳同时呈现（目标和掩蔽器在双耳中）、双耳分听，以及双耳分听但在双耳间切换目标和掩蔽器流。由于切换速率和信号连贯性预计会影响观察到的IM量，这两个因素在不同条件下有所变化。当发生切换时，它们要么在单词边界处，要么定期（每116毫秒）进行，并且在每个切换点处要么有短暂间隙（84毫秒），要么没有。此外，在安静条件下测量SRT以排除可听度作为限制因素。
四种切换双耳分听条件下的SRT比非切换双耳分听条件下的差，但比双耳同时呈现条件下的好。与其他切换条件相比，无间隙的定期切换导致最差的SRT，从而使IM最大化。
这些发现表明，在双耳间定期切换目标和掩蔽器流（无间隙）在破坏SRM方面最为有效。因此，这种方法可用于寻求相对纯净的IM测量的实验，并且可以很容易地扩展到转化研究中。
