Hillock-Dunn Andrea, Buss Emily, Duncan Nicole, Roush Patricia A, Leibold Lori J
1Department of Allied Health Sciences, The University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, North Carolina, USA; 2Department of Otolaryngology/Head and Neck Surgery, The University of North Carolina at Chapel Hill, School of Medicine Chapel Hill, North Carolina, USA.
Ear Hear. 2014 May-Jun;35(3):353-65. doi: 10.1097/AUD.0000000000000007.
This study evaluated effects of nonlinear frequency compression (NLFC) processing in children with hearing loss for consonant identification in quiet and for spondee identification in competing noise or speech. It was predicted that participants would benefit from NLFC for consonant identification in quiet when access to high-frequency information was critical, but that NLFC would be less beneficial, or even detrimental, when identification relied on mid-frequency cues. Further, it was hypothesized that NLFC could result in greater susceptibility to masking in the spondee task. The rationale for these predictions is that improved access to high-frequency information comes at the cost of decreased spectral resolution.
A repeated-measures design compared speech-perception outcomes in 17 pediatric hearing aid users (9 to 17 years of age) wearing Naida V SP "laboratory" hearing aids with NLFC on and off. Data were also collected in an initial baseline session in which children wore their personal hearing aids. Children with a wide range of audiometric configurations were included, but all participants were full-time users of hearing aids with active NLFC. For each hearing aid condition, speech perception was assessed in the sound field by using a closed-set 12-alternative consonant-vowel identification measure in quiet, and a closed-set four-alternative spondee-identification measure in a speech-shaped noise or in a two-talker speech masker.
No significant differences in performance were observed between laboratory hearing aid conditions with NLFC activated or deactivated for either speech-perception measure. An unexpected finding was that the majority of participants had no difficulty identifying the high-frequency consonant /s/ even when NLFC was deactivated. Investigation into individual differences revealed that subjects with a greater difference in audible bandwidth with NLFC on versus NLFC off were less likely to demonstrate improvements in high-frequency consonant identification in quiet, but were more likely to demonstrate improvements in spondee identification in speech-shaped noise. Group results observed in the initial baseline assessment using personal aids fitted with more aggressive NLFC settings than used in laboratory aids indicated better consonant identification accuracy in quiet. However, spondee identification in the two-talker masker was poorer with personal compared with laboratory hearing aids. Comparisons across personal and laboratory hearing aids are tempered, however, by the potential of an order effect.
The observation of comparable performance with NLFC on and NLFC off in the laboratory aids provides evidence that NLFC is neither detrimental nor advantageous when modest in strength. Results with personal hearing aids fitted with stronger compression settings than laboratory aids (NLFC on) highlight the critical need for further research to determine the impact of NLFC processing on speech perception for a wider range of speech-perception measures and compression settings.
本研究评估了非线性频率压缩（NLFC）处理对听力损失儿童在安静环境中识别辅音以及在竞争性噪声或言语环境中识别扬扬格词的影响。研究预测，当获取高频信息至关重要时，参与者在安静环境中识别辅音会从NLFC中受益，但当识别依赖中频线索时，NLFC的益处会减少，甚至可能产生不利影响。此外，研究假设NLFC可能会使扬扬格词任务中对掩蔽的敏感性更高。这些预测的依据是，改善高频信息的获取是以降低频谱分辨率为代价的。
采用重复测量设计，比较了17名佩戴奈达V SP“实验室”助听器且NLFC功能开启和关闭的儿科助听器使用者（9至17岁）的言语感知结果。还在初始基线阶段收集了数据，在此阶段儿童佩戴他们自己的助听器。纳入了听力图配置范围广泛的儿童，但所有参与者都是NLFC功能开启的助听器的全职使用者。对于每种助听器条件，通过在安静环境中使用封闭式12选1的辅音 - 元音识别测量方法以及在言语噪声或双说话者言语掩蔽环境中使用封闭式4选1的扬扬格词识别测量方法，在声场中评估言语感知。
对于任何一种言语感知测量方法，NLFC开启或关闭的实验室助听器条件下的表现均未观察到显著差异。一个意外发现是，即使NLFC关闭，大多数参与者在识别高频辅音/s/时也没有困难。对个体差异的调查显示，NLFC开启与关闭时可听带宽差异较大的受试者，在安静环境中高频辅音识别方面不太可能表现出改善，但在言语噪声中扬扬格词识别方面更有可能表现出改善。在初始基线评估中观察到的群体结果表明，使用比实验室助听器设置更强的NLFC功能的个人助听器，在安静环境中辅音识别准确性更高。然而，与实验室助听器相比，个人助听器在双说话者掩蔽环境中的扬扬格词识别较差。不过，由于可能存在顺序效应,个人助听器和实验室助听器之间的比较受到了影响。
在实验室助听器中观察到NLFC开启和关闭时表现相当，这证明当强度适当时，NLFC既无不利影响也无优势。配备比实验室助听器更强压缩设置（NLFC开启）的个人助听器的结果突出表明，迫切需要进一步研究，以确定NLFC处理对于更广泛的言语感知测量方法和压缩设置对言语感知的影响。
