Perreau Ann E, Bentler Ruth A, Tyler Richard S
Department of Communication Sciences and Disorders, Augustana College, IL, USA.
J Am Acad Audiol. 2013 Feb;24(2):105-20. doi: 10.3766/jaaa.24.2.4.
Frequency-lowering signal processing in hearing aids has re-emerged as an option to improve audibility of the high frequencies by expanding the input bandwidth. Few studies have investigated the usefulness of the scheme as an option for bimodal users (i.e., combined use of a cochlear implant and a contralateral hearing aid). In this study, that question was posed.
The purposes of this study were (1) to determine if frequency compression was a better bimodal option than conventional amplification and (2) to determine the impact of a frequency-compression hearing aid on speech recognition abilities.
There were two separate experiments in this study. The first experiment investigated the contribution of a frequency-compression hearing aid to contralateral cochlear implant (CI) performance for localization and speech perception in noise. The second experiment assessed monaural consonant and vowel perception in quiet using the frequency-compression and conventional hearing aid without the use of a contralateral CI or hearing aid.
Ten subjects fitted with a cochlear implant and hearing aid participated in the first experiment. Seventeen adult subjects with a cochlear implant and hearing aid or two hearing aids participated in the second experiment. To be included, subjects had to have a history of postlingual deafness, a moderate or moderate-to-severe hearing loss, and have not worn this type of frequency-lowering hearing aid previously.
In the first experiment, performance using the frequency-compression and conventional hearing aids was assessed on tests of sound localization, speech perception in a background of noise, and two self-report questionnaires. In the second experiment, consonant and vowel perception in quiet was assessed monaurally for the two conditions. In both experiments, subjects alternated daily between a frequency-compression and conventional hearing aid for 2 mo. The parameters of frequency compression were set individually for each subject, and audibility was measured for the frequency compression and conventional hearing aid programs by comparing estimations of the Speech Intelligibility Index (SII) using a modified algorithm (Bentler et al, 2011). In both experiments, the outcome measures were administered following the hearing aid fitting to assess performance at baseline and after 2 mo of use.
For this group of subjects, the results revealed no significant difference between the frequency-compression and conventional hearing aid on tests of localization and consonant recognition. Spondee-in-noise and vowel perception scores were significantly higher with the conventional hearing aid compared to the frequency-compression hearing aid after 2 mo of use.
These results suggest that, for the subjects in this study, frequency compression is not a better bimodal option than conventional amplification. In addition, speech perception may be negatively influenced by frequency compression because formant frequencies are too severely compressed and can no longer be distinguished.
助听器中的降频信号处理作为一种通过扩展输入带宽来提高高频可听度的方法再次出现。很少有研究调查该方案对双耳佩戴者（即同时使用人工耳蜗和对侧助听器）的有效性。本研究提出了这个问题。
本研究的目的是（1）确定频率压缩是否比传统放大更适合双耳佩戴，以及（2）确定频率压缩助听器对语音识别能力的影响。
本研究有两个独立的实验。第一个实验研究了频率压缩助听器对侧人工耳蜗（CI）在噪声中定位和语音感知性能的贡献。第二个实验评估了在安静环境中使用频率压缩助听器和传统助听器时的单耳辅音和元音感知，不使用对侧人工耳蜗或助听器。
10名佩戴人工耳蜗和助听器的受试者参与了第一个实验。17名成年人工耳蜗和助听器使用者或佩戴两个助听器的受试者参与了第二个实验。受试者必须有语后聋病史、中度或中度至重度听力损失，且之前未佩戴过此类降频助听器才能纳入研究。
在第一个实验中，使用频率压缩助听器和传统助听器在声音定位测试、噪声背景下的语音感知测试以及两份自我报告问卷上进行了性能评估。在第二个实验中，对两种情况分别进行了单耳安静环境下的辅音和元音感知评估。在两个实验中，受试者每天在频率压缩助听器和传统助听器之间交替使用2个月。针对每个受试者单独设置频率压缩参数，并通过使用改进算法（Bentler等人，2011年）比较语音清晰度指数（SII）估计值，来测量频率压缩和传统助听器程序的可听度。在两个实验中，在助听器适配后进行结果测量，以评估基线时和使用2个月后的性能。
对于这组受试者，结果显示在定位测试和辅音识别方面，频率压缩助听器和传统助听器之间没有显著差异。使用2个月后，与频率压缩助听器相比，传统助听器的噪声中单词识别和元音感知得分显著更高。
这些结果表明，对于本研究中的受试者，频率压缩不是比传统放大更好的双耳佩戴选择。此外，语音感知可能会受到频率压缩的负面影响，因为共振峰频率被过度压缩，无法再被区分。
