Fundamental frequency development in typically developing infants and infants with severe-to-profound hearing loss

The many functions of vocal learning

The capacity to learn novel vocalizations has evolved convergently in a wide range of species. Courtship songs of male birds or whales are often treated as prototypical examples, implying a sexually selected context for the evolution of this ability. However, functions of learned vocalizations in different species are far more diverse than courtship, spanning a range of socio-positive contexts from individual identification, social cohesion, or advertising pair bonds, as well as agonistic contexts such as territorial defence, deceptive alarm calling or luring prey. Here, we survey the diverse usages and proposed functions of learned novel signals, to build a framework for considering the evolution of vocal learning capacities that extends beyond sexual selection. For each function that can be identified for learned signals, we provide examples of species using unlearned signals to accomplish the same goals. We use such comparisons to generate hypotheses concerning when vocal learning is adaptive, given a particular suite of socio-ecological traits. Finally, we identify areas of uncertainty where improved understanding would allow us to better test these hypotheses. Considering the broad range of potential functions of vocal learning will yield a richer appreciation of its evolution than a narrow focus on a few prototypical species. This article is part of the theme issue 'Vocal learning in animals and humans'.

Cry features of healthy neonates who passed their newborn hearing screening vs. those who did not

OBJECTIVES

Temporal and fundamental frequency (fo) variations in infant cries provide critical insights into the maturity of vocal control and hearing performances. Earlier research has examined the use of vocalisation properties (in addition to hearing tests) to identify infants at risk of hearing impairment. The aim of this study was to determine whether such an approach could be suitable for neonates.

METHODS

To investigate this, we recruited 74 healthy neonates within their first week of life as our participants, assigning them to either a group that passed the ABR-based NHS (PG, N = 36) or a group that did not, but were diagnosed as normally hearing in follow-up check at 3 months of life, a so-called false-positive group (NPG, N = 36). Spontaneously uttered cries (N = 2330) were recorded and analysed quantitatively. The duration, minimum, maximum and mean fo, as well as two variability measures (fo range, fo sigma), were calculated for each cry utterance, averaged for individual neonates, and compared between the groups.

RESULTS

A multiple analysis of variance (MANOVA) revealed no significant effects. This confirms that cry features reflecting vocal control do not differ between healthy neonates with normal hearing, irrespective of the outcome of their initial NHS.

CONCLUSIONS

Healthy neonates who do not pass the NHS but are normal hearing in the follow-up (false positive cases) have the same cry properties as those with normal hearing who do. This is an essential prerequisite to justify the research strategy of incorporating vocal analysis into NHS to complement ABR measures in identifying hearing-impaired newborns.

Validation of Auscultation Technologies using Objective and Clinical Comparisons

Technology is rapidly changing the health care industry. As new systems and devices are developed, validating their effectiveness in practice is not trivial, yet it is essential for assessing their technical and clinical capabilities. Digital auscultations are new technologies that are changing the landscape of diagnosis of lung and heart sounds and revamping the centuries old original design of the stethoscope. Here, we propose a methodology to validate a newly developed digital stethoscope, and compare its effectiveness against a market-accepted device, using a combination of signal properties and clinical assessments. Data from 100 pediatric patients is collected using both devices side by side in two clinical sites. Using the proposed methodology, we objectively compare the technical performance of the two devices, and identify clinical situations where performance of the two devices differs. The proposed methodology offers a general approach to verify a new digital auscultation device as clinically-viable; while highlighting the important consideration for clinical conditions in performing these evaluations.

Six month-old infants with deformational plagiocephaly do not differ from unaffected infants with respect to vocal control

OBJECTIVES

The recommendation of a supine sleeping position led to a significant reduction of SIDS, but increased positional skull deformities (DP). Here, a quantitative analysis of babbling aims to complement previous studies of language-relevant competence based on items of the Bayley-scales that suggested the presence of developmental language delays in DP infants. Measures of fundamental frequency variability as proxies for vocal control are well suited for testing this assumption, since the laryngeal neuro-muscular system matures early and is coupled with brain function while working rapidly in coordinating the structures and mechanisms involved in infant sound production.

METHODS

Sixty-six healthy, full-term infants with normal hearing and a monolingual background took part: (1) moderately asymmetrical DP group - N = 41; 21 male; (2) severely asymmetrical DP group - N = 10; 8 male; and (3) controls - N = 15; 5 male (group assignment based on stereophotogrammetric 360° scans). Fundamental frequency (fo) measures were taken as proxies for vocal control skills during babbling.

RESULTS

A MANOVA revealed no significant multivariate effect for the shape group, Wilks' λ = 0.86, F(2, 63) = 1.21, p = 0.30, η2 = 0.07 (medium effect-size). The results do not support previous findings based on Bayley scale evaluations that suggested a negative impact of DP on language development during infancy.

CONCLUSIONS

A strong link between DP and brain dysfunction affecting vocal control, which would cause deviations in otherwise healthy DP infants, was not observed. Objective long-term studies of sound production are necessary to identify and/or understand the potential consequences of DP on early language development.

Developing a reference of normal lung sounds in healthy Peruvian children

PURPOSE

Lung auscultation has long been a standard of care for the diagnosis of respiratory diseases. Recent advances in electronic auscultation and signal processing have yet to find clinical acceptance; however, computerized lung sound analysis may be ideal for pediatric populations in settings, where skilled healthcare providers are commonly unavailable. We described features of normal lung sounds in young children using a novel signal processing approach to lay a foundation for identifying pathologic respiratory sounds.

METHODS

186 healthy children with normal pulmonary exams and without respiratory complaints were enrolled at a tertiary care hospital in Lima, Peru. Lung sounds were recorded at eight thoracic sites using a digital stethoscope. 151 (81%) of the recordings were eligible for further analysis. Heavy-crying segments were automatically rejected and features extracted from spectral and temporal signal representations contributed to profiling of lung sounds.

RESULTS

Mean age, height, and weight among study participants were 2.2 years (SD 1.4), 84.7 cm (SD 13.2), and 12.0 kg (SD 3.6), respectively; and, 47% were boys. We identified ten distinct spectral and spectro-temporal signal parameters and most demonstrated linear relationships with age, height, and weight, while no differences with genders were noted. Older children had a faster decaying spectrum than younger ones. Features like spectral peak width, lower-frequency Mel-frequency cepstral coefficients, and spectro-temporal modulations also showed variations with recording site.

CONCLUSIONS

Lung sound extracted features varied significantly with child characteristics and lung site. A comparison with adult studies revealed differences in the extracted features for children. While sound-reduction techniques will improve analysis, we offer a novel, reproducible tool for sound analysis in real-world environments.

Data-driven automated acoustic analysis of human infant vocalizations using neural network tools

Acoustic analysis of infant vocalizations has typically employed traditional acoustic measures drawn from adult speech acoustics, such as f(0), duration, formant frequencies, amplitude, and pitch perturbation. Here an alternative and complementary method is proposed in which data-derived spectrographic features are central. 1-s-long spectrograms of vocalizations produced by six infants recorded longitudinally between ages 3 and 11 months are analyzed using a neural network consisting of a self-organizing map and a single-layer perceptron. The self-organizing map acquires a set of holistic, data-derived spectrographic receptive fields. The single-layer perceptron receives self-organizing map activations as input and is trained to classify utterances into prelinguistic phonatory categories (squeal, vocant, or growl), identify the ages at which they were produced, and identify the individuals who produced them. Classification performance was significantly better than chance for all three classification tasks. Performance is compared to another popular architecture, the fully supervised multilayer perceptron. In addition, the network's weights and patterns of activation are explored from several angles, for example, through traditional acoustic measurements of the network's receptive fields. Results support the use of this and related tools for deriving holistic acoustic features directly from infant vocalization data and for the automatic classification of infant vocalizations.