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Listeners are able to classify talkers by regional dialect of their native language when provided with even short speech samples. However, the way in which American English listeners use segmental and prosodic information to make such decisions is largely unknown. This study used a free classification task to assess native American English listeners' ability to group together talkers from six major dialect regions of American English. Listeners residing in Ohio and Texas were provided with a sentence-long (experiment 1) or paragraph-long (experiment 2) speech sample produced by talkers from each of the six regions presented in one of three conditions: unmodified, monotonized (i.e., flattened F0), and low-pass filtered (i.e., spectral information above 400 Hz removed). In both experiments, listeners in the unmodified and monotonized conditions made more accurate groupings, reflecting their reliance on segmental properties for classifying regional variation. Accuracy was highest for Northern and Western talkers (experiment 1) and Mid-Atlantic talkers (experiment 2). Listeners with experience with multiple dialects as a result of geographic mobility did not show increased accuracy, suggesting a complex relationship between linguistic experience and the perception of available acoustic cues to socioindexical variation.

The perception of the lexical pitch accents was examined in the Trøndersk dialect of Norwegian. Based on a production study, a categorization of stimuli with manipulated pitch contours was conducted. The experiment tested which acoustic cues (height and alignment of fundamental frequency (F0) minimum, and alignment of F0 maximum and turning point from maximum to minimum) are necessary for the perception of the tonal contrast. The results are consistent with the production findings in that changes in all of the examined acoustic cues contributed to the shift in accent categorization. The later alignment of the main F0 landmarks (F0 maximum, F0 minimum and turning point from maximum to minimum) induced accent 2 identification. Raising F0 minimum height also led to more accent 2 responses. The analysis of the perception patterns furthermore revealed that the effect of a later alignment of F0 minimum was weak unless combined with a later alignment of the other F0 landmarks, or a higher F0 minimum level, all of which contributed to more accent 2 responses. These results indicate that accent 1 is characterized by an early fall, and accent 2 by a salient initial high tone. Implications of these findings for the phonological analysis of the tonal contrasts in the Trøndersk dialect are also discussed.

Though necessary, protective mask wearing in response to the Covid-19 pandemic presents communication challenges. Speech produced through these masks is quieter, muffled, and lacks important visual cues for listeners. The present study examines how such loss of visual information and signal degradation affects intelligibility and auditory memory of non-native speech. Additionally, we examined whether clear speaking style can alleviate some perceptual difficulty for masked speech. One non-native English speaker recorded short, educationally relevant video clips in three conditions: casual speech without a mask, and casual and clear speech with a mask. In an online study, native English listeners were presented with 15 video clips in each of the three mask / style conditions and transcribed what they heard. Following each condition, listeners answered questions about the content of the clips. Word recognition and memory accuracy will be analyzed. Detailed acoustic analyses will be conducted to assess how face masks and speaking style affect speech production. The results will allow us to quantify speech communication challenges arising from the widespread use of masks. The findings will have implications for communication in classrooms and hospitals where listeners have to understand teachers and healthcare providers, often time non-native speakers, through their protective barriers.

Speaking clearly improves intelligibility particularly in noisy environments—a benefit that may be partly attributed to enhanced ease of speech segmentation. However, speech segmentation is facilitated by coarticulation (Fernandes et al., 2007), which may be reduced in hyper-articulated clear speech (Scarborough and Zellou, 2013). This study investigated the effect of clear speech on speech segmentation in quiet and in noise for native and non-native listeners with an artificial language (AL) learning experiment. Six trisyllabic AL words (e.g., /kutupi/) were produced by a native English speaker both clearly and conversationally. Six speech streams were created, each containing 20 pitch-flattened tokens of each AL word concatenated in random order without intervening pauses. In the learning phase, participants heard either conversational or clear AL speech streams in quiet or masked with speech-shaped noise. Next, in a two-alternative forced-choice test, participants identified the AL words spoken in quiet and in the style they were exposed to. Preliminary results showed that clear speech improved segmentation relative to conversational speech for native English listeners in quiet only. The results suggest that the use of exaggerated information about segment identity aids speech segmentation in optimal listening conditions but is disrupted under perceptual load.

This article provides an overview of the research concerning the nature of the distinct, listener-oriented speaking style called ‘clear speech’ and its effect on intelligibility for various listener populations. We review major findings that identify talker, listener and signal characteristics that contribute to the characteristically high intelligibility of clear speech. Understanding the interplay of these factors sheds light on the interaction between higher level cognitive and lower-level sensory and perceptual factors that affect language processing. Clear speech research is, thus, relevant for both its theoretical insights and practical applications. Throughout the review, we highlight open questions and promising future directions.

Much of daily communication occurs under a range of suboptimal conditions related to talker, listener, and signal characteristics. These “adverse” conditions (Mattys et al., 2012) increase intelligibility variation and impact perceptual processes, representations, attention, and memory functions. In this talk, I focus on two factors that condition intelligibility variation, namely, when interlocutors are non-native speakers of a target language and when communication occurs in noise. First, I will discuss a set of experiments examining how native and non-native talkers modify their speech with the goal of enhancing their intelligibility and the extent to which these modifications enhance word recognition in noise for native and non-native listeners. I also present results from studies examining how listeners adapt to more and less familiar foreign accents of varying intelligibility when presented in noise. These studies provide insights into the interplay between physical and mental factors in the production and perception of intelligible speech. They further reveal constraints on talker-listener adaptation processes during communication. A detailed understanding of speech intelligibility variation for native and non-native talkers and listeners will enhance our understanding of the compensatory and cognitive mechanisms that allow speech comprehension in naturalistic conditions.

Previous work indicates that listeners are able to adapt quickly to changes in accent [Clarke & Garrett, 2004; Bradlow & Bent, 2008] and that adaptation is faster for familiar accents [Witteman et al., 2013; Blanco et al., 2014]. The present study examines how listeners adapt to more and less familiar accents presented in noise as compared to quiet, since noisy listening environments are more perceptually challenging [Vaden et al., 2013; Gilbert et al., 2014] but also more closely represent typical listening conditions. Native English listeners heard blocks of sentences produced by native- or foreign-accented talkers (Korean, Spanish) and responded to a visual probe. Listener accuracy and reaction times were compared across accent and speaker blocks. Results showed that, unlike in quiet, listeners were unable to adapt to the less-familiar Korean accent. Processing of the familiar Spanish accent was successful in noise and quiet. Adaptation in noise was furthermore correlated with talker intelligibility: less intelligible talkers elicited lower accuracy and slower response; in quiet, there was no talker effect. The results revealed that the ability to adapt to a novel foreign accent is disrupted, as the extra perceptual effort in noise prevents listeners from generalizing about systematic variability of foreign-accented features.

The role of visual cues in native listeners' perception of speech produced by nonnative speakers has not been extensively studied. Native perception of English sentences produced by native English and Korean speakers in audio-only and audiovisual conditions was examined. Korean speakers were rated as more accented in audiovisual than in the audio-only condition. Visual cues enhanced word intelligibility for native English speech but less so for Korean-accented speech. Reduced intelligibility of Korean-accented audiovisual speech was associated with implicit visual biases, suggesting that listener-related factors partially influence the efficiency of audiovisual integration for nonnative speech perception.

Purpose In this study, the authors examined how signal clarity interacts with the use of sentence context information in determining speech-in-noise recognition for children with cochlear implants and children with normal hearing. Method One hundred and twenty sentences in which the final word varied in predictability (high vs. low semantic context) were produced in conversational and clear speech. Nine children with cochlear implants and 9 children with normal hearing completed the sentence-in-noise listening tests and a standardized language measure. Results Word recognition in noise improved significantly for both groups of children for high-predictability sentences in clear speech. Children with normal hearing benefited more from each source of information compared with children with cochlear implants. There was a significant correlation between more developed language skills and the ability to use contextual enhancements. The smaller context gain in clear speech for children with cochlear implants is in accord with the effortfulness hypothesis (McCoy et al., 2005) and points to the cumulative effects of noise throughout the processing system. Conclusion Modifications of the speech signal and the context of the utterances through changes in the talker output hold substantial promise as a communication enhancement technique for both children with cochlear implants and children with normal hearing.

Purpose The authors sought to investigate interactions among intelligibility-enhancing speech cues (i.e., semantic context, clearly produced speech, and visual information) across a range of masking conditions. Method Sentence recognition in noise was assessed for 29 normal-hearing listeners. Testing included semantically normal and anomalous sentences, conversational and clear speaking styles, auditory-only (AO) and audiovisual (AV) presentation modalities, and 4 different maskers (2-talker babble, 4-talker babble, 8-talker babble, and speech-shaped noise). Results Semantic context, clear speech, and visual input all improved intelligibility but also interacted with one another and with masking condition. Semantic context was beneficial across all maskers in AV conditions but only in speech-shaped noise in AO conditions. Clear speech provided the most benefit for AV speech with semantically anomalous targets. Finally, listeners were better able to take advantage of visual information for meaningful versus anomalous sentences and for clear versus conversational speech. Conclusion Because intelligibility-enhancing cues influence each other and depend on masking condition, multiple maskers and enhancement cues should be used to accurately assess individuals' speech-in-noise perception.

Perceptual compensation for speaker vocal tract properties was investigated in four groups of listeners: native speakers of English and native speakers of Dutch, native speakers of Spanish with low proficiency in English, and Spanish–English bilinguals. Listeners categorized targets on a [sofo] to [sufu] continuum. Targets were preceded by sentences that were manipulated to have either a high or a low F1 contour. All listeners performed the categorization task for targets that were preceded by Spanish, English and Dutch precursors. Results show that listeners from each of the four language backgrounds compensate for speaker vocal tract properties regardless of language-specific vowel inventory properties. Listeners also compensate when they listen to stimuli in another language. The results suggest that patterns of compensation are mainly determined by auditory properties of precursor sentences.

Purpose The purpose of this study was to examine sentence-recognition performance for a large, diverse group of nonnative speakers of English on the recently developed Basic English Lexicon (BEL) sentence materials and to determine whether BEL sentence lists are equated in difficulty for this population. Method The BEL sentences were presented to 102 nonnative speakers of English with normal hearing and varied linguistic and cultural backgrounds. Five hundred sentences were presented mixed with noise spectrally matched to the target sentences. Subjects completed an online questionnaire providing detailed demographic and linguistic information. Listeners' spoken English proficiency was also assessed using the Versant English Test (Pearson Education, 2010). Results Nonnative listeners showed equal word-recognition performance for 3 groups of BEL sentence lists, each group containing sentence lists that had equivalent difficulty. In addition, spoken language proficiency and several demographic and linguistic factors were significantly correlated with BEL performance. Conclusion The BEL sentence materials have been tested on a large cohort of nonnative speakers of English and have been found to be appropriate for use in speech-perception testing with this population.

Signal distortions are more detrimental to speech perception by native than non-native listeners. We investigated how speech clarity and semantic context influence the perception of interrupted speech. Native and non-native American English listeners heard semantically meaningful or anomalous sentences produced as conversational or “clear” speech, gated at different rates (0.5–16 Hz). Results showed that both semantic context and speech clarity had a significant rate-dependent impact on the intelligibility of interrupted speech. In general, intelligibility was higher for native than non-native listeners. However, the magnitude of the clear-speech benefit varied across the two listener groups. The clear-speech benefit was obtained for gating rates of 2 Hz and above, except for meaningful sentences with native listeners where the benefit begin at 1 Hz. Both listener groups were able to use contextual information but native listeners derived more benefit at lower gating rates, indicating greater ability to a...

This study investigated the time-course of word recognition in adverse listening conditions. Specifically, we examined the effect of different listener-oriented speaking styles and semantic context on lexical access in quiet and in noise. Young adult listeners participated in an online visual word recognition experiment. They heard sentences with a high- versus low-predictability semantic context, produced in Conversational (CO), Infant-Directed (IDS), and Clear (CS) speech while fixating two pictures on a screen: a target that matched the last word of the auditory stimulus and a distractor. All sentences were presented either in quiet, or mixed with speech-shaped noise at a −5 dB SNR. Results showed that IDS provided similar perceptual benefits to adult listeners as CS. Relative to low-predictability CO baseline, IDS and CS increased speed of word recognition for high-predictability sentences, in quiet and in noise equally. However, in the quiet condition, lexical access was eventually facilitated by contextual cues even in CO, but listeners in noise reliably focused the target only when a combination of contextual cues and exaggerated acoustic-phonetic cues was available. These findings suggest that both semantic cues and listener-oriented acoustic enhancements are needed for reliable and rapid lexical access, especially in adverse conditions.

Listeners adapt quickly to changes in accent (Bradlow & Bent, 2003; Clarke & Garrett, 2004; inter alia). The cause of this brief delay may be due to the cost of processing accented speech, or may reflect a surprise effect associated with task expectations (Floccia et al., 2009). The present study examines a link between accent familiarity and processing delays with listeners who have varying degrees of familiarity with target languages: monolingual Texans with little or no formal exposure to Spanish, early Spanish-English bilinguals, and Korean learners of English. Participants heard four blocks of English sentences—Blocks 1 and 4 were produced by two native speakers of American English, and Blocks 2 and 3 were produced by native speakers of Spanish or Korean- and responded to written probe words. All listener groups responded more slowly after an accent change; however, the degree of delay varied with language proficiency. L1 Korean listeners were less delayed by Korean-accented speech than the other listeners, while changes to Spanish-accented speech were processed most slowly by Spanish-English bilinguals. The results suggest that adaptation to foreign-accented speech depends on language familiarity and task expectations. The processing delays are analyzed in light of intelligibility and accentedness measures.

Previous research has found that listener-oriented speaking style adaptations, such as Infant Directed Speech (IDS) and Clear Speech (CS), aid perception and development and improve intelligibility for children and adults, respectively. However, less is known about whether these different speaking styles enhance intelligibility in general, or if young children benefit most from IDS features aimed at capturing and maintaining attention. Additionally, information about time course differences in word recognition for these speech modifications has not been investigated. This study investigates both questions by presenting young adult listeners with semantically anomalous and meaningful sentences produced in IDS, CS, and Conversational (CO) Speech. Listeners participated in (1) a word-recognition-in-noise test and (2) a visual word recognition paradigm tracking eye movements. Results showed facilitated word recognition in noise for both IDS and CS compared to CO. Both speaking style adjustments also resulted in increased speed of word recognition in the visual paradigm. Semantic context provided additional facilitation only when more exaggerated acoustic cues were present (in IDS and CS). Preliminary analyses show that even for adult listeners IDS provided the greatest perceptual benefits, indicating that established advantages of IDS for young listeners cannot be mainly attributed to affect in addition to enhanced acoustic cues.

A change in speaker accent is reported to temporarily slow speech processing (Bradlow and Bent, 2003; Clarke and Garrett. 2004). Recent work suggests that this delay may be an artifact of task expectations and reflects a surprise effect, not the time needed for accent adaptation (Floccia et al., 2009). The present study tested listeners with high and low exposure to Spanish- and Korean-accented English to determine if frequent exposure to these accents decreases the surprise effect in an experimental setting. Participants listened to four blocks of meaningful sentences and responded to probe words; they heard a native-accented speaker in the first block and either native-, Spanish- or Korean-accented speakers in blocks 2 and 3. Results thus far show that the change from native-accented to foreign-accented speaker (block 1 to block 2) elicited a processing delay for participants in the Korean-accented condition, but not in the Spanish-accented condition. This pattern remained, but was somewhat attenuated, in the change from block 2 to block 3, when voice but not accent changed. These results show that extensive experience with a particular foreign accent (Spanish) outside the lab results in a smaller processing cost when listening to accented speech in the lab.

The influence of speech clarity on the perception of interrupted speech was examined for sentences distinguished by the presence of semantic-contextual cues. Semantically meaningful and anomalous sentences produced in either conversational or "clear" speech were periodically interrupted at gating rates ranging from slow (0.5 Hz) to fast (24 Hz) and presented to 26 native English listeners. At slow rates, speech perception may be based on integration of whole syllables and words, with "glimpsing" of (sub)phonemic segments playing a role at faster rates. Our results show that semantic context and speech clarity had a significant rate-dependent impact on the intelligibility of interrupted speech. At the lowest rates, intelligibility differences between conditions were minimal. Overall, interruption was most deleterious for anomalous conversational sentences. Such effects were seen even at the highest gating rate of 24 Hz for which interruption effects are generally minimal. The magnitude of the clear-speech benefit varied with gating rate for the two types of sentences, starting at 1 Hz for meaningful and 2 Hz for anomalous sentences. Acoustic-phonetic enhancements of clear speech thus "shifted" contextual benefit to lower gating rates. The implications of these results for our understanding of different time scales of speech processing will be discussed.

Even though the US population is becoming more diverse, there are no normalized sentence recognition tests for non-native English listeners. Recently, a large set of new test materials aimed at assessing speech recognition and hearing abilities for native and non-native listeners were developed by Smiljanic and Calandruccio [J. Acoust. Soc. Am. 128(4), 2486]. Five hundred unique sentences divided into 20 lists were created. The target keywords were chosen from the most frequent lexical items occurring in naturally elicited conversations with 100 non-native talkers with varied linguistic and cultural backgrounds. The lists were equalized for syntactic structure, syllable count, high-frequency phonemes, and word frequency. Perception results revealed equal mean performance across lists for native listeners. Currently, we are in the process of collecting normative data for these materials. Results of speech-in-noise tests for a diverse group of non-native English listeners with various native language backgrounds and levels of English experience will be presented. Regression analyses will be performed to investigate how the listeners' linguistic experience, competence, and proficiency relate to their listening performance on these new sentence-recognition materials. The results of this study add to our current understanding of non-native listener-related factors that affect speech recognition in adverse listening conditions.

Though the US population is becoming more diverse, there are no normalized sentence recognition tests for non‐native English listeners. It is, therefore, difficult to examine sources of perceptual problems in speech recognition tasks by non‐native listeners in laboratory and audiology clinics. The goal of this project is to develop test materials appropriate for assessing non‐native listeners’ speech recognition and hearing abilities. In order to limit linguistic biases, we recorded naturally elicited conversations with 100 non‐native talkers from 28 nations and with 15 different native languages on 20 topics. The recordings were transcribed and a lexicon of over 5000 unique words was compiled. The most frequent words across speakers of varying proficiency levels and language backgrounds were used to create test sentences with an equal number of keywords and with the syntactic structure appropriate for non‐native listeners. The sentences will be recorded by four native talkers of English and evaluated for...

Previous work has established that elderly adult’s comprehension is more detrimentally affected by noise, multi‐talker babble and the absence of contextual cues compared to younger adult’s comprehension. Elderly adult’s abilities to understand fast speech and to detect/recognize brief non‐speech and speech sound sequences (e.g., stop gaps) also decline with age. These effects seem to persist even when hearing loss is taken into account. In this study, we explored whether there are parallel effects of age on speech production, i.e., whether elderly adult’s production patterns differ from those of younger adults. Specifically, we examined whether elderly and younger adult’s hyper‐articulation clear speech strategies provide similar intelligibility advantage for younger adult listeners. The sentence‐in‐noise perception results revealed that elderly adult’s clear speech increased intelligibility for young adult listeners. Importantly, the overall elderly adult’s speech intelligibility and the clear speech intelligibility gain were smaller compared to that provided by the speech of younger adults. Acoustic correlates of the differences in the observed clear speech gain provided by older and younger adults are explored. These results suggest that, in addition to perceptual problems, cognitive and hearing changes due to age can affect elderly adult’s speech patterns and intelligibility.

The speech of sleep‐deprived persons has been variously described as more “slurred” or “tired‐sounding” than speech by the same speakers in a rested condition. Although sleep deprivation is a major focus of research for public safety and health reasons, there has been notably little research on the connection between sleep deprivation and speech. Using an automatic system for detecting “landmarks”, i.e., important perceptual and articulatory events in the acoustic signal, we compared sleep‐deprived and rested speech recorded during two well‐controlled studies of sleep deprivation. Our results show that sleep‐deprived speech is significantly different from rested speech for both the number and pattern of landmarks detected. These results are similar in detail to differences previously found between clear and conversational styles of speech. The relevance of these findings for speech as a marker of sleep‐deprivation will be discussed, along with potential applications in public safety and health. [Research supported by NIH.]

This study investigated how native language background (L1) interacts with speaking style in determining levels of speech intelligibility. In four experiments, we explored whether native and non‐native hyper‐articulation clear speech strategies provide similar intelligibility benefits for native and high proficiency non‐native listeners. The sentence‐in‐noise perception results revealed that native speech was preferred over non‐native speech by both listener groups even when non‐native talkers and listeners shared the same L1. Clear speech was shown to be beneficial for both the native and fluent non‐native listeners. However, non‐native clear speech enhanced intelligibility less than native clear speech, supporting the hypothesis that clear speech production strategies involve enhancement of language‐specific phonological contrasts. In order to assess the relationship between objective intelligibility measures and subjective accentedness ratings, we obtained accentedness ratings of native and non‐native conversational and clear speech by native and non‐native listeners. The results showed that objective intelligibility and subjective accentedness were independent. Overall, these results provide strong evidence that clear speech involves language‐specific modifications. Nevertheless, native and high proficiency non‐native clear speech modifications are generally helpful for both native and high proficiency non‐native listeners even when the objective intelligibility and subjective accentedness levels diverged for various listener and talker groups.

Previous research showed that phonological neighborhood density and word frequency influence word recognition (Luce and Pisoni, 1998) and vowel production (Wright, 2002; Munson and Solomon, 2004; Munson, to appear), suggesting an interaction of lexical and phonetic factors in speech production and perception Here, we explore whether hyperarticulated, intelligibility‐enhancing clear speech shows similar sensitivity to lexical‐level structure. Nine American English talkers (five females, four males) produced 40 monosyllabic easy (frequent words with few lexical neighbors) and hard (infrequent words with many lexical neighbors) words in conversational and clear speech. Twenty‐four subjects participated in a word‐in‐noise listening test. Results revealed a large effect of style on intelligibility and vowel production: words were more intelligible and vowels were longer and more dispersed in clear compared to conversational speech. Moreover, the female talkers produced larger vowel spaces than male talkers in both speaking styles. Vowels in hard words were marginally more dispersed than vowels in easy words in both speaking styles. However, within both speaking styles, easy and hard words were equally intelligible and of approximately equal duration. These results showed that phonetic properties of vowels were enhanced equally in clear speech regardless of their lexical properties.

This paper examines the interaction of language‐general, signal enhancement strategies and language‐specific, phonological enhancement strategies in clear speech production and perception in Croatian, a language with a phonemic vowel length contrast and a relatively small inventory of five vowel qualities. Two native speakers of Croatian (one male, one female) read 20 nonsense sentences in conversational and clear speech. In a sentence‐in‐noise perception test, native Croatian listeners more accurately recognized words produced in clear than in conversational speech by both talkers. However, this clear speech intelligibility benefit was greater for the male than the female talker. Acoustic analyses showed that in clear speech both talkers enhanced the overall acoustic salience of the signal (slower, more frequent pauses, wider pitch range) and expanded the vowel space, although the male showed slightly less extensive vowel space expansion. However, only the male talker enhanced the phonemic vowel length c...