Keidser G, Grant F
The National Acoustic Laboratories, Chatswood, Australia.
Ear Hear. 2001 Dec;22(6):516-27. doi: 10.1097/00003446-200112000-00007.
The recently introduced NAL-NL1 rationale for fitting WDRC devices prescribes a relatively high compression threshold and prescribes compression ratios lower than those prescribed by loudness normalization rationales. The aim of this study was to investigate whether the compression characteristic prescribed by NAL-NL1 is most effective in a single-channel scheme or in a multi-channel scheme.
Twenty-four subjects with flat or steeply sloping hearing loss participated in the study. One, two, and four channels were implemented digitally in the laboratory and evaluated on the basis of a paired-comparison test and a speech recognition test. The test stimuli consisted of speech and noise presented at average input levels, and speech and noise alternating every 3 sec among different input levels. The single-channel and 2-channel NAL-NL1 prescriptions were also evaluated in individually selected everyday situations in the field using a digital 2-memory device.
The three compression schemes produced no significant difference in speech recognition scores. Most subjects showed no preference for either scheme in the paired-comparison test. Those who did mainly selected the single-channel scheme. These preferences can be explained on the basis on audibility and quality. In the field all subjects with a steeply sloping loss, but one, preferred the 2-channel scheme. Among the subjects with a flat loss more preferred the single-channel scheme than preferred the 2-channel scheme. Statistical analyses showed that those who preferred the 2-channel scheme were fitted with significantly greater differences in the compression ratio in the high frequencies, and those who preferred the single-channel scheme were fitted with significantly greater differences in the high-frequency gain for a 65 dB input.
Multi-channel compression prescribed according to NAL-NL1 in up to four channels showed no adverse effects on speech recognition relative to a single-channel scheme. The paired-comparison test showed a small, but explainable preference for the single-channel scheme. The field test revealed a preference for the 2-channel scheme by subjects with steeply sloping loss. When using the NAL-NL1 rationale it is recommended to use at
最近引入的用于适配宽动态范围压缩（WDRC）设备的NAL-NL1原理规定了相对较高的压缩阈值，并规定了比响度归一化原理更低的压缩比。本研究的目的是调查NAL-NL1规定的压缩特性在单通道方案还是多通道方案中最有效。
24名患有平坦或陡降型听力损失的受试者参与了本研究。在实验室中以数字方式实现了一通道、两通道和四通道，并基于配对比较测试和言语识别测试进行评估。测试刺激包括以平均输入水平呈现的言语和噪声，以及在不同输入水平之间每3秒交替一次的言语和噪声。单通道和两通道NAL-NL1处方也在现场使用数字双存储设备在个体选择的日常情况下进行了评估。
三种压缩方案在言语识别分数上没有显著差异。在配对比较测试中，大多数受试者对两种方案都没有偏好。有偏好的受试者主要选择了单通道方案。这些偏好可以根据可听度和质量来解释。在现场，除一名受试者外，所有患有陡降型听力损失的受试者都更喜欢两通道方案。在患有平坦型听力损失的受试者中，更喜欢单通道方案的人比更喜欢两通道方案的人更多。统计分析表明，更喜欢两通道方案的人在高频的压缩比差异显著更大，而更喜欢单通道方案的人在65分贝输入时高频增益的差异显著更大。
根据NAL-NL1规定的多达四通道的多通道压缩相对于单通道方案对言语识别没有不利影响。配对比较测试显示对单通道方案有轻微但可解释的偏好。现场测试显示患有陡降型听力损失的受试者更喜欢两通道方案。使用NAL-NL1原理时，建议使用……
