Evaluation of spectral enhancement in hearing aids, combined with phonemic compression.

In this study, the separate and combined effects on speech perception of compensation of the reduced dynamic range by compression and compensation of the reduced frequency resolution by spectral enhancement is investigated. The study has been designed to compare the effects of signal processing on monosyllabic consonant-vowel-consonant words for hearing-impaired listeners in conditions of quiet, fluctuating noise, and continuous noise. Speech perception of spectrally enhanced speech was compared with unprocessed speech. In addition, a comparison was made between combinations of spectrally enhanced speech and two types of phonemic compression. In the past, the definition "syllabic compressor" is often used to indicate fast compressors. However, the time constants of the fast compressors used in this study are so short that syllabic has become an inappropriate term. Moreover, intelligibility tests were performed in which scores were acquired of monosyllabic words, and their constituent "phonemic" parts. Therefore, the definitions "phoneme" and phonemic will be used throughout this paper. In one condition, spectral enhancement produced significant improvements for vowel perception. But, this was counteracted by deterioration of the consonant scores for all but one subject. In general, the best overall scores for consonant-vowel-consonant words were obtained in the unprocessed condition. After the spectral enhancement, a single-channel phonemic compressor added no improvement. There are indications that a multichannel phonemic compressor and spectral enhancement have opposite effects, because the scores for this combination are, in general, the lowest.

Design of two syllabic nonlinear multichannel signal processors and the results of speech tests in noise.

OBJECTIVE: Multichannel syllabic compressors have not yet shown clear advantages for speech perception. New multichannel syllabic nonlinear processors are designed and evaluated in this study to test whether they enhance speech perception scores. DESIGN: Nonsense consonant-vowel-consonant words have been processed in real time with two syllabic nonlinear methods in nine different frequency channels: 1) 30 dB of speech information is mapped into the residual dynamic range (DR) of the subjects with hearing impairment using either compression or expansion; 2) speech levels above the rms level are compressed with a ratio of 3:1, and input levels below the rms level are mapped into the reduced DR of the subjects. The overall frequency spectrum of speech is tilted with more high-frequency output for this condition. The two syllabic nonlinear processors were compared with two linear reference systems (one of them with the same spectral tilt as the second nonlinear condition) for seven hearing-impaired subjects. RESULTS: On average, the syllabic nonlinear processors show scores similar to one of the linear systems. The linear reference with tilt has, on average, 3% higher scores, mainly due to improved vowel identification. CONCLUSIONS: No negative effects were shown on average for the syllabic nonlinear processors, but no positive effects were demonstrated either. Tilting of the overall speech spectrum was advantageous.

The effects of an interactive instructional strategy for enhancing reading comprehension and content area learning for students with learning disabilities.

This study investigated the effectiveness of an interactive vocabulary instructional strategy, semantic-feature analysis (SFA), on the content area text comprehension of adolescents with learning disabilities. Prior to reading a social studies text, students in resource classes either completed a relationship chart as part of the SFA condition or used the dictionary to write definitions and sentences as part of the contrast condition. Passage comprehension was measured on a multiple-choice test consisting of two types of items, vocabulary and conceptual. Comprehension was measured immediately following teaching and again 6 months after teaching. Prior knowledge for the content of the passage served as a covariate. Results indicated that students in the SFA instructional condition had significantly greater measured comprehension immediately following and 6 months after initial teaching. These results are discussed in relation to concept-driven, interactive strategies for teaching content and facilitating text comprehension.

Inferential reading abilities of mildly mentally retarded and nonretarded students.

The inferential operations of mildly mentally retarded students reading at the intermediate level were investigated using methods based on discourse comprehension theory. We hypothesized that problems encountered in reading by these students are related to difficulties in generating logical inferences. Mildly retarded junior-high students and nonretarded third-grade students of the same reading comprehension level read and recalled a descriptive expository and a narrative passage. On the expository passage mildly retarded students generated the same quantity of inferences as did nonretarded students, but the inferences were qualitatively inferior. On the narrative passage the differences between the two groups were not significant. These findings were discussed in relation to the cognitive functioning of mildly retarded students.