A human factors experiment was conducted to assess the intelligibility of synthesized speech under a variety of noise conditions for both hearing-impaired and normal-hearing subjects. Modified Rhyme Test stimuli were used to determine intelligibility in four speech-to-noise (S/N) ratios (0, 5, 10, and 15 dB), and three noise types, consisting of flat-by-octaves (pink) noise, interior noise of a currently produced heavy truck, and truck cab noise with added background speech. A quiet condition was also investigated. During recording of the truck noise for the experiment, in-cab noise measurements were obtained. According to OSHA standards, these data indicated that drivers of the sampled trucks have a minimal risk for noise-induced hearing loss due to in-cab noise exposure when driving at freeway speeds because noise levels were below 80 dBA. In the intelligibility experiment, subjects with hearing loss had significantly lower intelligibility than normal-hearing subjects, both in quiet and in noise, but no interaction with noise type or S/N ratio was found. Intelligibility was significantly lower for the noise with background speech than the other noises, but the truck noise produced intelligibility equal to the pink noise. An analytical prediction of intelligibility using Articulation Index calculations exhibited a high positive correlation with the empirically obtained intelligibility data for both groups of subjects. / Master of Science

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The speech of a person speaking in a noisy environment can be enhanced through electronic beamforming using spatially distributed microphones. As this approach demands precise information about the microphone locations, its application is limited in places where microphones must be placed quickly or changed on a regular basis. Highly precise calibration or measurement process can be tedious and time consuming. In order to understand tolerable limits on the calibration process, the impact of microphone position error on the intelligibility is examined. Analytical expressions are derived by modeling the microphone position errors as a zero mean uniform distribution. Experiments and simulations were performed to show relationships between precision of the microphone location measurement and loss in intelligibility. A variety of microphone array configurations and distracting sources (other interfering speech and white noise) are considered. For speech near the threshold of intelligibility, the results show that microphone position errors with standard deviations less than 1.5cm can limit losses in intelligibility to within 10% of the maximum (perfect microphone placement) for all the microphone distributions examined. Of different array distributions experimented, the linear array tends to be more vulnerable whereas the non-uniform 3D array showed a robust performance to positional errors.

The main goal of this doctoral thesis was to measure differences in speech intelligibility between older and younger hearing-impaired people and to establish the factors influencing the effectiveness of the use of hearing aids in the elderly. We focused on three related areas: 1/ To measure how the magnitude of difference of hearing and speech intelligibility in silence differs between younger and older populations, with a similar degree of hearing loss, in terms of word audiometry. 2/ To establish how speech intelligibility in competitive noise differs between younger and older populations with a similar degree of auditory defect, in terms of the Czech Test of Sentence Intelligibility in Babble Noise. 3/ To establish which factors affect the effectiveness of hearing aids for seniors, the motivation for the acquisition and regular use of hearing aids, and whether these factors correlate with age or lifestyle. Methodology 1/ A group of 143 hearing aid users was divided into young (N = 60, mean age 15,9 y.) and seniors (N = 83, mean age 83,6 y.). For these two age groups we compared the differences between SRT values (understanding in word audiometry in silence, in the free field) and PTA values (hearing threshold in pure tone audiometry). 2/ A group of 423 persons, examined using the Test of...

The goal of this study was to investigate the methodology in designing a vowel intelligibility model that can objectively predict the outcome of a vowel confusion test performed with normal hearing individuals listening to a cochlear implant acoustic model. The model attempts to mimic vowel perception of a cochlear implantee mathematically. The output of the model is the calculated probability of correct identification of vowel tokens and the probability of specific vowel confusions in a subjective vowel confusion test. In such a manner, the model can be used to aid cochlear implant research by complementing subjective listening tests. The model may also be used to test hypotheses concerning the use and relationship of acoustic cues in vowel identification. The objective vowel intelligibility model consists of two parts: the speech processing component (used to extract the acoustic cues which allow vowels to be identified) and the decision component (simulation of the decision making that takes place in the brain). Acoustic cues were extracted from the vowel sounds and used to calculate probabilities of identifying or confusing specific vowels. The confusion matrices produces by the objective vowel perception model were compared with results from subjective tests performed with normal hearing listeners listening to an acoustic cochlear implant model. The most frequent confusions could be predicted using the first two formant frequencies and the vowel duration as acoustic cues. The model could predict the deterioration of vowel recognition when noise was added to the speech being evaluated. The model provided a first approximation of vowel intelligibility and requires further4 development to completely predict speech perception of cochlear implantees. / Dissertation (ME)--University of Pretoria, 2009. / Electrical, Electronic and Computer Engineering / unrestricted

Speech intelligibility of voice alarm communication systems is extremely important for proper notification and direction of building occupants. Currently, there is no minimum standard to which all voice alarm communication systems must be held. Tests were conducted to determine how system and room characteristics, and the addition of occupants, affect the intelligibility of a voice signal. This research outlines a methodology for measuring the speech intelligibility of a room and describes the impact of numerous variables on these measurements. Eight variables were considered for this study: speaker quantity and location, speaker power tap, sound pressure level (SPL), number and location of occupants, presence of furniture, location of intelligibility measurements, data collection method, and floor covering. All room characteristics had some affect on the room intelligibility; the sound pressure level of the signal and the number and location of occupants had the greatest overall impact on the intelligibility of the room. It is recommended, based on the results of this study, that further investigation be conducted in the following areas: floor finishes, speaker directivity, various population densities, furniture packages and room sizes.

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Tystnad kan användas som ett kognitivt verktyg för att påverka en filmupplevelse och för att förhöja vissa audiovisuella aspekter. Denna studie undersöker hur tystnad som berättargrepp inom genren sci-fi kan användas genom två koncept för ljudinspelning: fidelity, som är en trogen ljudinspelning av vad som visas i bild, och intelligibility, som adderar ljud för narrativ information. Koncepten lät oss som ljuddesigners analysera och kontrollera tystnadsögonblicken i varje scenario. Point of audition användes som ett adderat designverktyg för att fokusera tystnadsögonblicken i narrativet. Genom diskussion i fokusgrupper kunde vi utvärdera hur tystnaden upplevdes i varje separat klipp. Studien visade att tystnad som berättargrepp föredrogs vid en kombination av de två koncepten. / Silence can be used as a cognitive tool to influence a film experience and to elevate certain audiovisual aspects. This study examines how silence as a narrative technique in the sci-fi genre can be used through two concepts for sound recording: fidelity, which is a faithful sound recording of what is shown on screen, and intelligibility, which adds sound for narrative information. The concepts allowed us as sound designers to analyze and control the moments of silence in each scenario. Point of audition was used as an added design tool to focus the moments of silence in the narrative. Through discussions in focus groups, we were able to evaluate how the silence was experienced in each separate clip. The study showed that silence as a narrative approach was preferred in a combination of the two concepts.

Background speech is annoying and distracting when working on tasks that require focus, and according to previous research, background speech is a common cause of reduced work performance. According to the interference-by-process theory, distraction is a function of the similarity between the processes involved in the involuntary analysis of the background speech and the voluntary processes involved in the task. In view of this theory, a similarity in language—between the produced language and the language that is listened to—may increase the magnitude of distraction by background chatter in comparison with when the language which is produced is different from the language that is perceived. The purpose of the present experiment was to investigate whether work performance—as indexed by writing fluency (WF)—varies depending on the similarity between the language that is heard in the background and the language that is produced. The experiment had a within-participants design with two factors: language to-be-produced (Swedish vs. English) and language of the background speech (Swedish vs. English). The sample constituted of 43 university students, with Swedish as native language. The result showed a main effect of language to-be-produced: WF increased when the participants produced text in their native language compared to text production in their second language. No main effect of language of background speech was found, and no interaction between these two factors was revealed.