Acoustic-phonetic characteristics of speech produced with communicative intent to counter adverse listening conditions

This study investigated whether speech produced in spontaneous interactions when addressing a talker experiencing actual challenging conditions differs in acoustic-phonetic characteristics from speech produced: (a) with communicative intent under more ideal conditions, and (b) without communicative intent under imaginary challenging conditions (read, clear speech). It also investigated whether acoustic-phonetic modifications made to counteract the effects of a challenging listening condition are tailored to the condition under which communication occurs. 40 talkers were recorded in pairs while engaged in ‘spot the difference’ picture tasks in good and challenging conditions. In the challenging conditions, one talker heard the other: (1) via a three-channel noise vocoder (VOC); (2) with simultaneous babble noise (BABBLE). Read, clear speech showed more extreme changes in median F0, F0 range and speaking rate than speech produced to counter the effects of a challenging listening condition. In the VOC condition, where F0 and intensity enhancements are unlikely to aid intelligibility, talkers did not change their F0 median and range; mean energy and vowel F1 increased less than in the BABBLE condition. This suggests that speech production is listener-focused, and that talkers modulate their speech according to their interlocutors’ needs, even when not directly experiencing the challenging listening condition

Is Consonant Perception Linked to Within-Category Dispersion or Across-Category Distance?

This study investigated the relation between the internal structure of phonetic categories and consonant intelligibility. For two phonetic contrasts (/s/-/S/ and /b/-/p/), 32 iterations per category were elicited for each of 40 talkers from a same accent group and age range, and measures of cross-category distance and within-category dispersion were obtained. These measures varied substantially across talkers but were not correlated across both contrasts suggesting that degree of cross-category distance or within-category dispersion is not consistent within-speaker. For each contrast, consonant identification tests in mild babble noise, that presented the complete set of iterations for eight talkers showing extreme values in these two measures, revealed some talker effects on reaction time. However, these did not appear to be correlated with either cross-category distance or within-category dispersion for those talkers

Acoustic-Phonetic Characteristics of Clear Speech in Bilinguals

This study examined the language-dependency of clear speech modifications by comparing the clear speech strategies of late bilinguals in both their L1 (Finnish) and L2 (English). Results generally supported the hypothesis of language-independent enhancement of global clear speech modifications, but language-dependent segmental enhancement. The global clear speech strategies produced by Finnish-English bilinguals in their L2 (English) were similar in the extent of the modifications to those of native English speakers, indicating a surprising flexibility of the non-native speech production system

Do talkers produce less dispersed phoneme categories in a clear speaking style?

This study investigated whether adaptations made in clear speaking styles result in more discriminable phonetic categories than in a casual style. Multiple iterations of keywords with word-initial /s/-/ʃ/ were obtained from 40 adults in casual and clear speech via picture description. For centroids, cross-category distance increased in clear 8 speech but with no change in within-category dispersion and no effect on discriminability. However, talkers produced fewer tokens with centroids in the ambiguous region for the /s/-/ʃ/ distinction. These results suggest that, whereas interlocutor feedback regarding communicative success may promote greater segmental adaptations, it is not necessary for some adaptation to occur

Clear Speech strategies and speech perception in adverse listening conditions

The study investigated the impact of different types of clear speech on speech perception in an adverse listening condition. Tokens were extracted from spontaneous speech dialogues in which participants completed a problem-solving task in good listening conditions or while experiencing a one-sided ‘communication barrier’: a real-time vocoder or multibabble noise. These two adverse conditions induced the ‘unimpaired’ participant to produce clear speech. When tokens from these three conditions were presented in multibabble noise, listeners were quicker at processing clear tokens produced to counter the effects of multibabble noise than clear tokens produced to counteract the vocoder, or tokens produced in good communicative conditions. A clarity rating experiment using the same tokens presented in quiet showed that listeners do not distinguish between different types of clear speech. Together, these results suggest that clear speaking styles produced in different communicative conditions have acoustic-phonetic characteristics adapted to the needs of the listener, even though they may be perceived as being of similar clarity

Close-up analysis of aircraft ice accretion

Various types of ice formation have been studied by analysis of high magnification video observations. All testing was conducted in the NASA Lewis Icing Research Tunnel (IRT). A faired 8.9 cm (3.5 in.) diameter metal-clad cylinder and a 5.1 (2 in.) aluminum cylinder were observed by close-up and overview video cameras for several wind tunnel conditions. These included close-up grazing angle, close-up side view, as well as overhead and side overview cameras. Still photographs were taken at the end of each spray along with tracings of the subsequent ice shape. While in earlier tests only the stagnation region was observed, the entire area from the stagnation line to the horn region of glaze ice shapes was observed in this test. The modes or horn formation have been identified within the range of conditions observed. In the horn region, Horn Type A ice is formed by 'dry' feather growth into the flow direction and Horn Type B is formed by a 'wet' growth normal to the surface. The feather growth occurs when the freezing fraction is near unity and roughness elements exist to provide an initial growth site

Inapproximability of maximal strip recovery

In comparative genomic, the first step of sequence analysis is usually to decompose two or more genomes into syntenic blocks that are segments of homologous chromosomes. For the reliable recovery of syntenic blocks, noise and ambiguities in the genomic maps need to be removed first. Maximal Strip Recovery (MSR) is an optimization problem proposed by Zheng, Zhu, and Sankoff for reliably recovering syntenic blocks from genomic maps in the midst of noise and ambiguities. Given $d$ genomic maps as sequences of gene markers, the objective of \msr{d} is to find $d$ subsequences, one subsequence of each genomic map, such that the total length of syntenic blocks in these subsequences is maximized. For any constant $d \ge 2$, a polynomial-time 2d-approximation for \msr{d} was previously known. In this paper, we show that for any $d \ge 2$, \msr{d} is APX-hard, even for the most basic version of the problem in which all gene markers are distinct and appear in positive orientation in each genomic map. Moreover, we provide the first explicit lower bounds on approximating \msr{d} for all $d \ge 2$. In particular, we show that \msr{d} is NP-hard to approximate within $\Omega(d/\log d)$. From the other direction, we show that the previous 2d-approximation for \msr{d} can be optimized into a polynomial-time algorithm even if $d$ is not a constant but is part of the input. We then extend our inapproximability results to several related problems including \cmsr{d}, \gapmsr{\delta}{d}, and \gapcmsr{\delta}{d}.Comment: A preliminary version of this paper appeared in two parts in the Proceedings of the 20th International Symposium on Algorithms and Computation (ISAAC 2009) and the Proceedings of the 4th International Frontiers of Algorithmics Workshop (FAW 2010

An acoustic-phonetic comparison of the clear speaking styles of late Finnish-English bilinguals

Research on clear speech, an intelligibility-enhancing speaking style, has proposed that global clear speech modifications which make speech more perceptible in adverse conditions are language-independent, while the more fine-grained segmental clear speech modifications, which enhance the salience of phonological contrasts, are language-specific [Bradlow, A.R. & Bent, T., 2002. The clear speech effect for non-native listeners. Journal of the Acoustical Society of America, 112, 272–284]. This study assessed the claim by contrasting the clear speech strategies used by twelve Finnish-English late bilinguals in their two languages, using spontaneous speech and sentence reading tasks. Their global clear speech modifications were also compared to those of native English speakers. Global measures included mean energy between 1-3k Hz, f0 median and range, and speech rate, while segmental measures included VOT for initial stop consonants and vowel spectral and temporal characteristics for two vowel contrasts. The global clear speech strategies of late bilinguals approximated those of native English speakers. Findings generally support the hypothesis that global enhancements are language-independent while segmental enhancements are language-dependent: the late bilinguals enhanced some of the segmental detail differently in clear speech according to the language being spoken, but most of the global clear speech modifications were consistent across languages

The impact of variation in phoneme category structure on consonant intelligibility

Newman et al. [J. Acoustic. Soc. Am, 109, 1181-1196 (2001)] suggested that phoneme identification accuracy and speed for a given talker was affected by the degree of variability in their production of phoneme categories. This study investigates how intra-talker variability in the production of two phoneme contrasts varies with age and gender, and how this variability affects perception. Multiple iterations of tokens differing in initial consonants (/s/-/ʃ/, /p/-/b/) were collected via picture elicitation from 40 adults and 31 children aged 11 to 14; measures of within-category dispersion, between-category distance, overlap and discriminability were obtained. While females produced more discriminable categories than males, children produced farther yet more dispersed - and thus similarly discriminable - categories than adults. Variability was contrast-specific rather than a general talker characteristic. Tokens with initial /s/-/ʃ/ from pairs of adult and child talkers varying in between-category distance or overlap were presented for identification. The presence of overlap had a greater effect on identification accuracy and speed than between-category distance, with strongest effects for adult speakers, but reaction time correlated most highly with within category dispersion. These data suggest that talkers who are less consistent in their speech production may be perceived less clearly than more internally-consistent talkers