Expanded vowel or tone space in IDS has traditionally been interpreted as evidence of enhanced acoustic contrasts. However, emerging evidence from various languages shows that the within-category acoustic variability of vowels and tones also increases in IDS, offsetting the benefit of space expansion and leading to non-enhanced, or reduced acoustic contrasts. This study re-analysed a corpus of Mandarin IDS and ADS, showing that, relative to ADS, vowels and tones in IDS display greater variability, resulting in non-enhanced contrasts. Thus, given increased variability, expanded vowel or tonal space in IDS may not necessarily equate to enhanced acoustic contrasts.

We obtained 24 air samples in 8 general wards temporarily converted into negative-pressure wards admitting coronavirus disease 2019 (COVID-19) patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) omicron variant BA.2.2 in Hong Kong. SARS-CoV-2 RNA was detected in 19 (79.2%) of 24 samples despite enhanced indoor air dilution. It is difficult to prevent airborne transmission of SARS-CoV-2 in hospitals.

Producing word-initial /s/-stop clusters can be a challenge for English-speaking pre-schoolers. For children with hearing loss (HL), fricatives can be also difficult to perceive, raising questions about their production and representation of /s/-stop clusters. The goal of this study was therefore to determine if pre-schoolers with HL can produce and represent the /s/ in word-initial /s/-stop clusters, and to compare this to their normal hearing (NH) peers. Based on both acoustic and perceptual analysis, we found that children with HL had little /s/-omission, suggesting that their phonological representation of these clusters closely aligns with that of their NH peers.

Learning to use word versus phrase level prosody to identify compounds from lists is thought to be a protracted process, only acquired by 11 years (Vogel & Raimy, 2002). However, a recent study has shown that 5-year-olds can use prosodic cues other than stress for these two structures in production, at least for early-acquired noun-noun compounds (Yuen et al., 2021). This raises the question of whether children this age can also use naturally-produced prosody to identify noun-noun compounds from their list forms in comprehension. The results show that 5-6-year-olds (N = 28) can only identify compounds. Unlike adults, children as a group could not use boundary cues to identify lists and were significantly slower in their processing compared to adults. This suggests that the acquisition of word level prosody may precede the acquisition of phrase level prosody, i.e., some higher-level aspects of phrasal prosody may take longer to acquire.

While voicing contrasts in word-onset position are acquired relatively early, much less is known about how and when they are acquired in word-coda position, where accurate production of these contrasts is also critical for distinguishing words (e.g., dog vs. dock). This study examined how the acoustic cues to coda voicing contrasts are realized in the speech of 4-year-old Australian English-speaking children. The results showed that children used similar acoustic cues to those of adults, including longer vowel duration and more frequent voice bar for voiced stops, and longer closure and burst durations for voiceless stops along with more frequent irregular pitch periods. This suggests that 4-year-olds have acquired productive use of the acoustic cues to coda voicing contrasts, though implementations are not yet fully adult-like. The findings have implications for understanding the development of phonological contrasts in populations for whom these may be challenging, such as children with hearing loss.

Universal masking for healthcare workers and patients in hospitals was adopted to combat coronavirus disease 2019 (COVID-19), with compliance rates of 100% and 75.9%, respectively. Zero rates of nosocomial influenza A, influenza B, and respiratory syncytial virus infection were achieved from February to April 2020, which was significantly lower than the corresponding months in 2017–2019.

Although previous research has indicated that five-year-olds can use acoustic cues to disambiguate compounds (N1 + N2) from lists (N1, N2) (e.g., ‘ice-cream’ vs. ‘ice, cream’) (Yoshida & Katz, 2004, 2006), their productions are not yet fully adult-like (Wells, Peppé & Goulandris, 2004). The goal of this study was to examine this issue in Australian English-speaking children, with a focus on their use of F0, word duration, and pauses. Twenty-four five-year-olds and 20 adults participated in an elicited production experiment. Like adults, children produced distinct F0 patterns for the two structures. They also used longer word durations and more pauses in lists compared to compounds, indicating the presence of a boundary in lists. However, unlike adults, they also inappropriately inserted more pauses within the compound, suggesting the presence of a boundary in compounds as well. The implications for understanding children's developing knowledge of how to map acoustic cues to prosodic structures are discussed.

Seasonal influenza virus epidemics have a major impact on healthcare systems. Data on population susceptibility to emerging influenza virus strains during the interepidemic period can guide planning for resource allocation of an upcoming influenza season. This study sought to assess the population susceptibility to representative emerging influenza virus strains collected during the interepidemic period. The microneutralisation antibody titers (MN titers) of a human serum panel against representative emerging influenza strains collected during the interepidemic period before the 2018/2019 winter influenza season (H1N1-inter and H3N2-inter) were compared with those against influenza strains representative of previous epidemics (H1N1-pre and H3N2-pre). A multifaceted approach, incorporating both genetic and antigenic data, was used in selecting these representative influenza virus strains for the MN assay. A significantly higher proportion of individuals had a ⩾four-fold reduction in MN titers between H1N1-inter and H1N1-pre than that between H3N2-inter and H3N2-pre (28.5% (127/445) vs. 4.9% (22/445), P < 0.001). The geometric mean titer (GMT) of H1N1-inter was significantly lower than that of H1N1-pre (381 (95% CI 339–428) vs. 713 (95% CI 641–792), P < 0.001), while there was no significant difference in the GMT between H3N2-inter and H3N2-pre. Since A(H1N1) predominated the 2018–2019 winter influenza epidemic, our results corroborated the epidemic subtype.

Phonological processes can pose a learning challenge for children, where the surface form for an underlying contrast may vary as a function of the phonological environment. Mandarin tone sandhi is a complex phonological process that requires knowledge about both the tonal and the prosodic context in which it applies. The present study explored the productive knowledge of tone sandhi processes by 108 3- to 5-year-old Mandarin-speaking children and 33 adults. Participants were asked to produce novel tone sandhi compounds in different tonal contexts and prosodic structures. Acoustic analysis showed that 3-year-olds have abstracted the tone sandhi process and can productively apply it to novel disyllabic words across tonal contexts. However, even 5-year-olds still differed from adults in applying tone sandhi in response to the trisyllabic prosodic structure. The results are discussed in terms of the factors that influence how tone sandhi processes, and phonological alternations more generally, are acquired.

Weak syllables in Germanic and Romance languages have been reported to be challenging for young children, with syllable omission and/or incomplete reduction persisting till age five. In Mandarin Chinese, neutral tone (T0) involves a weak syllable with varied pitch realizations across (preceding) tonal contexts and short duration. The present study examined how and when T0 was acquired by 108 Beijing Mandarin-speaking children (3–5 years) relative to 33 adult controls. Lexicalized (familiar) and non-lexicalized (unfamiliar) T0 words were elicited in different preceding tonal contexts. Unlike previous reports, the present study revealed that children as young as three years have already developed a phonological category for T0, exhibiting contextually conditioned tonal realizations of T0 for both familiar and unfamiliar items. However, mastery of adult-like pitch and duration implementation of T0 is a protracted process not completed until age five. The implications for the acquisition of weak syllables more generally are discussed.

English has a word-minimality requirement that all open-class lexical items must contain at least two moras of structure, forming a bimoraic foot (Hayes, 1995).Thus, a word with either a long vowel, or a short vowel and a coda consonant, satisfies this requirement. This raises the question of when and how young children might learn this language-specific constraint, and if they would use coda consonants earlier and more reliably after short vowels compared to long vowels. To evaluate this possibility we conducted an elicited imitation experiment with 15 two-year-old Australian English-speaking children, using both perceptual and acoustic analysis. As predicted, the children produced codas more often when preceded by short vowels. The findings suggest that English-speaking two-year-olds are sensitive to language-specific lexical constraints, and are more likely to use coda consonants when prosodically required.

Young children's first attempts at CVC words are often realized with the final consonant being heavily aspirated or followed by an epenthetic vowel (e.g. cat /kæt/ realized as [kæth] or [kætə]). This has led some to propose that young children represent word-final (coda) consonants as an onset-nucleus sequence (CV.Cv) (e.g. Goad & Brannen, 2003), raising questions about the syllabic status of the final consonant. To address this issue, we conducted an acoustic analysis of a child's early production of CVC, CVCh, and CVCV words between the ages of 1;3 and 1;5. Aside from aspiration, the results showed that there were no significant acoustic differences between the CVC and CVCh forms. In contrast, there were systematic acoustic differences in C2 closure duration between the CVC/CVCh and CVCV target words, suggesting that at least some children learning English have early coda representations for monosyllabic CVC words, whether heavily aspirated or not.