Stelmachowicz P G, Dalzell S, Peterson D, Kopun J, Lewis D L, Hoover B E
Boys Town National Research Hospital, Omaha, Nebraska 68131, USA.
Ear Hear. 1998 Apr;19(2):131-8. doi: 10.1097/00003446-199804000-00005.
In recent years, wide dynamic range compression (WDRC) has been used with increasing success. To optimize the fit with this type of hearing aid circuitry, subjective measures of loudness growth often are used. Unfortunately, these type of measures cannot be performed with infants, young children, and some elderly individuals. The primary purpose of this study was to compare the fitting recommendations of two recently described threshold-based procedures for fitting nonlinear hearing aids (DSL 4.0 and FIG6) to the use gain settings of satisfied adult hearing aid users for whom the fitting was based on subjective measures of loudness growth. Because it cannot be assumed that the use settings for adults will be appropriate for young children, a secondary goal was to quantify the audibility of speech at the use settings derived from loudness growth measures.
Forty-nine adult hearing aid users with mild to severe sensorineural hearing loss participated in this study. For all subjects, loudness growth measures were used to optimize the fit of a 2-channel WDRC hearing aid. The use gain at 50 and 80 dB SPL was compared with the gain recommended by DSL, FIG6, and the manufacturer's threshold-based fitting algorithm.
In general, both DSL and FIG6 prescribed more gain than actually was used by these hearing aid wearers. These discrepancies increased as a function of frequency, and differences in excess of 20 dB were observed in some cases. The manufacturer's algorithm provided a closer approximation to the use gain than either DSL or FIG6. Utilizing these use gain values, an Aided Audibility Index (AAI) was calculated for soft, average, and loud speech across four degrees of hearing loss, ranging from mild to severe (12 conditions). Transfer functions for continuous discourse and nonsense syllables were applied to yield estimated intelligibility scores. For the higher context speech materials, estimated intelligibility was > or = 85% for nine of the 12 conditions. For low-context speech materials, estimated intelligibility was > or = 85% for only three of the 12 conditions.
Results suggest that the gain recommendations provided by both DSL and FIG6 exceeded the gain actually used by the adult hearing-impaired subjects in this study. Gain recommendations from the manufacturer's algorithm provided a closer approximation to the use gain values of these subjects. These findings suggest that, for adult hearing aid users who cannot perform loudness judgments reliably, the manufacturer's algorithm would be expected to provide a closer approximation to loudness-based use gain values than either DSL or FIG6. However, AAI calculations revealed that the gain recommendations from this algorithm produce adequate audibility of speech only if one assumes linguistic competence. When AAI values are transformed to predict the intelligibility of low-context speech materials, it appears that the degree of audibility may not be appropriate for prelingually hearing-impaired children with more than a moderate hearing loss.
近年来，宽动态范围压缩（WDRC）的应用越来越成功。为了优化与这类助听器电路的匹配，响度增长的主观测量方法经常被使用。不幸的是，这类测量方法无法应用于婴儿、幼儿和一些老年人。本研究的主要目的是比较最近描述的两种基于阈值的非线性助听器验配程序（DSL 4.0和FIG6）的验配建议与基于响度增长主观测量进行验配的成年助听器使用者的实际使用增益设置。由于不能假定成人的使用设置适用于幼儿，第二个目标是量化从响度增长测量得出的使用设置下言语的可听度。
49名患有轻至重度感音神经性听力损失的成年助听器使用者参与了本研究。对于所有受试者，使用响度增长测量来优化双通道WDRC助听器的验配。将50和80 dB SPL下的实际使用增益与DSL、FIG6以及制造商基于阈值的验配算法所推荐的增益进行比较。
总体而言，DSL和FIG6所规定的增益都超过了这些助听器佩戴者的实际使用增益。这些差异随频率增加，在某些情况下观察到超过20 dB的差异。制造商的算法比DSL或FIG6更接近实际使用增益。利用这些实际使用增益值，针对轻至重度四个听力损失程度（共12种情况）的软声、平均声和大声言语计算了助听听阈指数（AAI）。应用连续话语和无意义音节的传递函数来得出估计的可懂度分数。对于较高语境的言语材料，12种情况中有9种的估计可懂度≥85%。对于低语境的言语材料，12种情况中只有3种的估计可懂度≥85%。
结果表明，DSL和FIG6提供的增益建议超过了本研究中成年听力受损受试者的实际使用增益。制造商算法的增益建议更接近这些受试者的实际使用增益值。这些发现表明，对于无法可靠进行响度判断的成年助听器使用者，与DSL或FIG6相比，制造商的算法预计能更接近基于响度的实际使用增益值。然而，AAI计算表明，只有在假定语言能力的情况下，该算法的增益建议才能产生足够的言语可听度。当将AAI值转换以预测低语境言语材料的可懂度时，对于中度以上听力损失的语前聋儿童，可听度程度似乎并不合适。
