More Like this

1. Comparing Levenshtein distance and dynamic time warping in predicting listeners’ judgments of accent distance

   https://doi.org/10.1016/j.specom.2023.102987  

   Lind-Combs, Holly C.; Bent, Tessa; Holt, Rachael F.; Clopper, Cynthia G.; Brown, Emma (November 2023, Speech Communication)

   Listeners attend to variation in segmental and prosodic cues when judging accent strength. The relative contributions of these cues to perceptions of accentedness in English remains open for investigation, although objective accent distance measures (such as Levenshtein distance) appear to be reliable tools for predicting perceptual distance. Levenshtein distance, however, only accounts for phonemic information in the signal. The purpose of the current study was to examine the relative contributions of phonemic (Levenshtein) and holistic acoustic (dynamic time warping) distances from the local accent to listeners’ accent rankings for nine non-local native and nonnative accents. Listeners (n =52) ranked talkers on perceived distance from the local accent (Midland American English) using a ladder task for three sentence-length stimuli. Phonemic and holistic acoustic distances between Midland American English and the other accents were quantified using both weighted and unweighted Levenshtein distance measures, and dynamic time warping (DTW). Results reveal that all three metrics contribute to perceived accent distance, with the weighted Levenshtein slightly outperforming the other measures. Moreover, the relative contribution of phonemic and holistic acoustic cues was driven by the speaker’s accent. Both nonnative and non-local native accents were included in this study, and the benefits of considering both of these accent groups in studying phonemic and acoustic cues used by listeners is discussed. 

   more » « less
2. Relating pronunciation distance metrics to intelligibility across English accents

   https://doi.org/10.1016/j.wocn.2024.101357  

   Bent, Tessa; Henry, Malachi; Holt, Rachael F; Lind-Combs, Holly (November 2024, Journal of Phonetics)

   Unfamiliar accents can cause word recognition challenges, particularly in noisy environments, but few studies have incorporated quantitative pronunciation distance metrics to explain intelligibility differences across accents. To address this gap, intelligibility was measured for 18 talkers -- two from each of three first-language, one bilingual, and five second-language accents -- in quiet and two noise conditions. The relations between two edit distance metrics, which quantify phonetic differences from a reference accent, and intelligibility scores were assessed. Intelligibility was quantified through both fuzzy string matching and percent words correct. Both edit distance metrics were significantly related to intelligibility scores; a heuristic edit distance metric was the best predictor of intelligibility for both scoring methods. Further, there were stronger effects of edit distance as the listening condition increased in difficulty. Talker accent also contributed substantially to intelligibility models, but relations between accent and edit distance did not consistently pattern for the two talkers representing each accent. Frequency of production differences in vowels and consonants was negatively correlated with intelligibility, particularly for consonants. Together, these results suggest that significant amounts of variability in intelligibility across accents can be predicted by phonetic differences from the listener’s home accent. However, talker- and accent-specific pronunciation features, including suprasegmental characteristics, must be quantified to fully explain intelligibility across talkers and listening conditions. 

   more » « less
3. Predicting intelligibility from pronunciation distance metrics

   Bent, T.; Holt, R.F. (August 2023, Guarant International)

   Radek Skarnitzl & Jan Volín (Ed.)

   Unfamiliar native and non-native accents can cause word recognition challenges, particularly in noisy environments, but few studies have incorporated quantitative pronunciation distance metrics to explain intelligibility differences across accents. Here, intelligibility was measured for 18 talkers -- two from each of three native, one bilingual, and five non- native accents -- in three listening conditions (quiet and two noise conditions). Two variations of the Levenshtein pronunciation distance metric, which quantifies phonemic differences from a reference accent, were assessed for their ability to predict intelligibility. An unweighted Levenshtein distance metric was the best intelligibility predictor; talker accent further predicted performance. Accuracy did not fall along a native - non-native divide. Thus, phonemic differences from the listener’s home accent primarily determine intelligibility, but other accent- specific pronunciation features, including suprasegmental characteristics, must be quantified to fully explain intelligibility across talkers and listening conditions. These results have implications for pedagogical practices and speech perception theories. 

   more » « less
4. Dynamic acoustic vowel distances within and across dialects

   https://doi.org/10.1121/10.0032385  

   Clopper, Cynthia G (October 2024, The Journal of the Acoustical Society of America)

   Vowels vary in their acoustic similarity across regional dialects of American English, such that some vowels are more similar to one another in some dialects than others. Acoustic vowel distance measures typically evaluate vowel similarity at a discrete time point, resulting in distance estimates that may not fully capture vowel similarity in formant trajectory dynamics. In the current study, language and accent distance measures, which evaluate acoustic distances between talkers over time, were applied to the evaluation of vowel category similarity within talkers. These vowel category distances were then compared across dialects, and their utility in capturing predicted patterns of regional dialect variation in American English was examined. Dynamic time warping of mel-frequency cepstral coefficients was used to assess acoustic distance across the frequency spectrum and captured predicted Southern American English vowel similarity. Root-mean-square distance and generalized additive mixed models were used to assess acoustic distance for selected formant trajectories and captured predicted Southern, New England, and Northern American English vowel similarity. Generalized additive mixed models captured the most predicted variation, but, unlike the other measures, do not return a single acoustic distance value. All three measures are potentially useful for understanding variation in vowel category similarity across dialects. 

   more » « less
5. Generalized perceptual adaptation to second-language speech: Variability, similarity, and intelligibility

   https://doi.org/10.1121/10.0020914  

   Bradlow, Ann_R; Bassard, Adrianna_M; Paller, Ken_A (September 2023, The Journal of the Acoustical Society of America)

   Recent work on perceptual learning for speech has suggested that while high-variability training typically results in generalization, low-variability exposure can sometimes be sufficient for cross-talker generalization. We tested predictions of a similarity-based account, according to which, generalization depends on training-test talker similarity rather than on exposure to variability. We compared perceptual adaptation to second-language (L2) speech following single- or multiple-talker training with a round-robin design in which four L2 English talkers from four different first-language (L1) backgrounds served as both training and test talkers. After exposure to 60 L2 English sentences in one training session, cross-talker/cross-accent generalization was possible (but not guaranteed) following either multiple- or single-talker training with variation across training-test talker pairings. Contrary to predictions of the similarity-based account, adaptation was not consistently better for identical than for mismatched training-test talker pairings, and generalization patterns were asymmetrical across training-test talker pairs. Acoustic analyses also revealed a dissociation between phonetic similarity and cross-talker/cross-accent generalization. Notably, variation in adaptation and generalization related to variation in training phase intelligibility. Together with prior evidence, these data suggest that perceptual learning for speech may benefit from some combination of exposure to talker variability, training-test similarity, and high training phase intelligibility. 

   more » « less