Blamey P J, Dooley G J, James C J, Parisi E S
Department of Otolaryngology, University of Melbourne, Victoria, Australia.
Ear Hear. 2000 Feb;21(1):6-17. doi: 10.1097/00003446-200002000-00004.
The aim was to measure the loudness of monaural and binaural stimuli in a group of cochlear implant users who had residual hearing in the nonimplanted ear, and to consider the implications of these measures for a binaural fitting consisting of a hearing aid and an implant in opposite ears. Three independent hypotheses were addressed: that the shapes of the electric and acoustic loudness growth functions would be similar, although the dynamic ranges would differ; that standard implant and hearing aid fittings would result in substantial loudness mismatches between the acoustic and electric signals; and that loudness summation would occur for binaural combinations of electric and acoustic signals.
A modified version of the "Loudness Growth in 1/2-Octave Bands" method (Allen, Hall, & Jeng, 1990) was used to measure loudness growth for each ear of nine subjects. At the time of the experiment, the subject group included all implant users in Melbourne and Denver who were available for research and who also had sufficient residual hearing to use a hearing aid in the nonimplanted ear. Five acoustic frequencies and five electrodes were measured for each subject. The same subjects also estimated the loudness of a set of stimuli including monaural and binaural signals chosen to cover the loudness range from very soft to loud.
The shapes of the averaged loudness growth functions were similar in impaired and electrically stimulated ears, although the shapes of iso-loudness curves were quite different in the two ears, and dynamic ranges varied considerably. Calculations based on the psychophysical data demonstrated that standard fitting procedures for cochlear implants and hearing aids lead to a complex pattern of loudness differences between the ears. A substantial amount of loudness summation was observed for the binaural stimuli, with most summation occurring when the acoustic and electric components were of equal loudness. This is consistent with observations for subjects with normal hearing and subjects with bilaterally impaired hearing.
These experiments provide data on which criteria and methods for the binaural fitting of cochlear implants and hearing aids may be based. It is unlikely that standard monaural fitting methods for cochlear implants and hearing aids will result in balanced loudness between the two ears across a reasonably broad range of frequencies and levels. It is also likely that output levels of both devices will need to be reduced relative to a monaural fitting to compensate for the binaural summation of loudness in some listeners.
本研究旨在测量一组非植入耳仍有残余听力的人工耳蜗使用者单耳和双耳刺激的响度，并探讨这些测量结果对由助听器和对侧耳植入体组成的双耳验配的意义。研究了三个独立假设：电刺激和声学刺激的响度增长函数形状相似，但动态范围不同；标准的植入体和助听器验配会导致声学信号和电信号之间存在明显的响度失配；电刺激和声学信号的双耳组合会出现响度总和。
采用“1/2倍频程带响度增长”方法（Allen、Hall和Jeng，1990）的改进版本，测量9名受试者每只耳朵的响度增长。实验时，受试者组包括墨尔本和丹佛所有可供研究且非植入耳有足够残余听力以使用助听器的人工耳蜗使用者。为每位受试者测量了5个声学频率和5个电极。同一组受试者还估计了一组刺激的响度，这些刺激包括单耳和双耳信号，所选信号覆盖从非常轻柔到响亮的响度范围。
尽管双耳等响度曲线形状差异很大且动态范围差异显著，但受损耳和电刺激耳的平均响度增长函数形状相似。基于心理物理学数据的计算表明，人工耳蜗和助听器的标准验配程序会导致双耳之间出现复杂的响度差异模式。对于双耳刺激，观察到大量的响度总和，当声学和电刺激成分响度相等时，响度总和最为明显。这与正常听力受试者和双侧听力受损受试者的观察结果一致。
这些实验提供了可作为人工耳蜗和助听器双耳验配标准及方法依据的数据。人工耳蜗和助听器的标准单耳验配方法不太可能在相当宽的频率和强度范围内使双耳响度达到平衡。对于一些受试者，相对于单耳验配，可能还需要降低两种设备的输出水平，以补偿双耳响度总和。
