The present study examined the ability of 4th year students of Russian as a second language to use intonation to form intelligible questions. 25 speakers were recorded asking a question in which they were supposed to stress one word in the question using intonation, as is standard in Russian. They then received an intelligibility score based on whether the native Russian raters correctly understood that they were asking a question and what they were asking a question about. Additionally, native speakers rated the speech samples on accentedness, meaning how much the speech deviated from native norms and comprehensibility, meaning how difficult it was to understand the speaker. Both of these last two constructs, i.e., comprehensibility and accentedness were rated using a Likert scale. It was then examined whether there was correlation between intelligibility, comprehensibility and accentedness. This study found the L2 speakers of Russian were correctly understood as asking a question 89% of the time, but what the question was about was only correctly understood at a rate of 39%. Correlation was found between accentedness and comprehensibility, meaning that speakers with better accentedness also received higher comprehensibility scores. But no correlation was found between intelligibility and accentedness nor with comprehensibility. The study concludes with suggestions of why intonation is, in fact, important in communication and suggests areas for improvement in pedagogical settings as well as directions for future research which would include context-based dialogues and the use of Praat in judging statements.

Recent studies on pronunciation teaching in ESL classrooms have found that the teaching of suprasegmentals, namely stress, pausing, and intonation, has a great effect on improving intelligibility (Derwing, Munro, & Wiebe, 1998; Kang, Rubin, & Pickering, 2010; Morley, 1991). The current project describes the development and implementation of computer-based pronunciation materials used for an English for Specific Purposes (ESP) program. The pronunciation program made use of cued pronunciation readings (CPRs) which used suprasegmentals and were developed for English as a second language (ESL) missionaries at the Provo, Utah, Missionary Training Center (MTC). Because there was no pronunciation program in place at the MTC, instructional materials that focused on prosodic features were greatly needed. Missionaries participated in the program anywhere from three to six weeks. Results from the implementation period revealed that missionaries made medium to large gains in their ability to perceive suprasegmentals after using the practice tasks and small-medium gains in their ability to produce suprasegmentals during this short time period. Recommendations for further development, implementation, and testing of similar materials are made for use with individuals in other ESP settings like these missionaries at the MTC.

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A human factors experiment was conducted to assess whether a reduction in noise at the ear would cause an improvement in speech intelligibility, an improvement in cognitive performance, and/or a reduction in subjective mental workload. Modified Rhyme Test (MRT) stimuli were used to determine intelligibility and specific tests within the Complex Cognitive Assessment Battery (CCAB) were used to assess cognitive performance. The tests chosen from the CCAB were: Tower Puzzle, Logical Relations, and Numbers and Words. These tests were chosen because of the specific set of cognitive functions that they measure which corresponded to command and control tasks. Participants performed the MRT and CCAB tests simultaneously in a 114 dBA noise environment at two speech levels, 83 dB (linear) and 96 dB (linear), using two communication microphones, Gentex Model 1453 and a prototype communication microphone developed by Adaptive Technologies Inc. (ATI). The noise used in the experiment was from a recording made inside a US Army Bradley Fighting Vehicle. Subjective mental workload was assessed using the NASA-TLX and Modified Cooper-Harper (MCH) immediately after the experiment. Results indicated that the communication microphone developed by ATI reduced the noise level at the ear better than the current Gentex microphone. However, the Gentex microphone produced significantly higher speech intelligibility scores at the 96 dB speech level. Cognitive performance scores significantly improved with increasing speech level for both communication microphones, with the ATI microphone having the advantage at 83 dB and the Gentex at 96 dB. The results also indicated that the main effects of speech level and communication microphone did not have an effect on subjective mental workload. A correlation analysis revealed that there was a positive relationship between the two workload measurement tools, indicating that either scale may be used to assess mental workload. Therefore, it was concluded that the MCH could have been used instead of the NASA-TLX, since the overall workload score was of interest. / Ph. D.

Speech intelligibility tests using three headset systems, two passive and one with active noise reduction technology, were conducted. Nine listeners, six males and three females, responded to 180 50-word Modified Rhyme Word Lists presented under two noise conditions, two conditions of bilateral phase reversal of the speech signal, and the three headset systems. These three independent variables were studied in a full factorial within-subjects design. The noise conditions were pink noise and recordings from the troop carrying compartment of a U.S. Army M-2 Bradley Fighting Vehicle (tank noise having substantial low-frequency energy). Phase reversal of the speech signal was also tested for its effect on speech intelligibility. The three headset systems were the David Clark Noise Attenuating Aviation Headset, and the Bose Aviation Headset used in both its passive and active mode. Active noise reduction technology employs the physical principle of constructive and destructive interference by creating signals which are identical to the noise under the earmuff but out of phase by 180 degrees. This technology is most effective at frequencies below 1000 Hz. Results showed that the Bose headset in its active mode required a significantly higher speech-to-noise ratio in both noise environments than the two passive headset systems to achieve the 70% level of speech intelligibility, the dependent variable in this study. The mean speech level under the Bose headset in its active mode was 2.8 dB higher in tank noise and 3.5 dB higher in pink noise than under the David Clark headset. The Bose headset in the active mode, however, provided a greater degree of broadband attenuation especially in the lower frequency range, e.g. < 630 Hz. Phase reversal proved to be of no benefit to performance in either noise environment. The pink noise proved to be the harsher environment for speech intelligibility than did the tank noise, primarily due to the increased levels in the speech bandwidth. Articulation Index scores for the three headset systems evidenced that the differences in performance among the three headset systems were in part the result of better earphone response characteristics in the principal speech bandwidth (600 - 4000 Hz) in conjunction with the strong attenuation performance of the David Clark headset in that same range. It is suggested that, in the absence of better earphone response characteristics and a broader bandwidth of active noise reduction performance, speech intelligibility is no better under active noise reduction headsets than under quality passive headsets. Further, the levels of speech intelligibility attained by active noise reduction headsets are at a cost of increased signal strength and higher purchase price. / Ph. D.