Department of Special Education and Counselling, The Education University of Education, Hong Kong SAR, China.
Division of Speech and Hearing Sciences, Faculty of Education, The University of Hong Kong, Hong Kong SAR, China.
Ear Hear. 2020 May/Jun;41(3):532-538. doi: 10.1097/AUD.0000000000000774.
Lexical tone information provides redundant cues for the recognition of Mandarin sentences in listeners with normal hearing in quiet conditions. The contribution of lexical tones to Mandarin sentence recognition in listeners with hearing aids (HAs) is unclear. This study aimed to remove lexical tone information and examine the effects on Mandarin sentence intelligibility in HA users. The second objective was to investigate the contribution of cognitive abilities (i.e., general cognitive ability, working memory, and attention) on Mandarin sentence perception when the presentation of lexical tone information was mismatched.
A text-to-speech synthesis engine was used to manipulate Mandarin sentences into three test conditions: (1) a Normal Tone test condition, where no alterations were made to lexical tones within sentences; (2) a Flat Tone test condition, where lexical tones were all changed into tone 1 (i.e., the flat tone); and (3) a Random Tone test condition, where each word in test sentences was randomly assigned one of four Mandarin lexical tones. The manipulated sentence signals were presented to 32 listeners with HAs in both quiet and noisy environments at an 8 dB signal to noise ratio.
Speech intelligibility was reduced significantly (by approximately 40 percentage points) in the presence of mismatched lexical tone information in both quiet and noise. The difficulty in correctly identifying sentences with mismatched lexical tones among adults with hearing loss was significantly greater than that of adults with normal hearing. Cognitive function was not significantly related to a decline in speech recognition scores.
Contextual and other phonemic cues (i.e., consonants and vowels) are inadequate for HA users to perceive sentences with mismatched lexical tone contours in quiet or noise. Also, HA users with better cognitive function could not compensate for the loss of lexical tone information. These results highlight the importance of accurately representing lexical tone information for Mandarin speakers using HAs.
在安静环境下，正常听力的听众可以通过词汇音高信息对普通话句子进行冗余提示。助听后（HA）使用者对词汇音高在普通话句子识别中的贡献尚不清楚。本研究旨在去除词汇音高信息，研究其对 HA 用户普通话句子可懂度的影响。第二个目的是当词汇音高信息呈现不匹配时，调查认知能力（即一般认知能力、工作记忆和注意力）对普通话句子感知的贡献。
使用文语转换合成引擎对普通话句子进行三种测试条件的操作：（1）正常音高测试条件，句子中的词汇音高不变；（2）平音高测试条件，所有词汇音高均转换为 1 调（即平调）；（3）随机音高测试条件，测试句子中的每个词都随机分配为四个普通话词汇音高之一。在安静和嘈杂环境下，在 8 dB 信噪比处向 32 名 HA 使用者呈现处理后的句子信号。
在安静和噪声环境中，当词汇音高信息不匹配时，言语可懂度显著降低（约降低 40 个百分点）。与正常听力成年人相比，听力损失成年人正确识别不匹配词汇音高句子的难度明显更大。认知功能与言语识别评分下降无显著相关性。
语境和其他音位线索（即辅音和元音）不足以使 HA 使用者在安静或噪声中感知不匹配词汇音高轮廓的句子。此外，认知功能较好的 HA 用户无法弥补词汇音高信息的缺失。这些结果强调了为使用 HA 的普通话使用者准确表示词汇音高信息的重要性。
