摘要:

Systematic recordings were made at regular intervals (6, 9, 12, and 15 months) and utterances were transcribed and analyzed from speech samples of children at risk and not at risk to stutter. Children were audio and video recorded interacting with their own mother for 10‐min play periods. The purpose of the study was to gather quantitative information on fluency development prior to the diagnosis of a stuttering disorder to determine whether or not children can be differentiated based on vocal development. Wideband spectrograms and formant tracking displays were used to analyze oral development (plotting first and second formant frequencies of the steady‐state part of the vowel) and the other measurement pertained to laryngeal‐oral coordination (analyzing voice onset time in stop consonants). Acoustic analyses were performed using the Kay Elemetrics CSL workstation. Control subjects had more elaborated vowel systems than children who end up stuttering in their vocalizations. Pre‐stuttering children also displayed repetitive disfluencies in their vocal play. [Work supported by NIH and ASHF.]

ISSN:0001-4966    

DOI:10.1121/1.408794

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Word‐familiarity databases have usually been developed for visually presented words, not for auditorily presented words. The purpose of this study is to develop a familiarity database for both auditorily and visually presented words, and to investigate the relationship between both representations. Using a 7‐point scale, ten Japanese adults rated the familiarity of every word in the Shinmeikai Japanese dictionary (Tokyo: Sansei‐do, 1974)—about 62 000 words. The words were auditorily presented to each subject in one session and visually presented in another. The Pearson correlation coefficient between the auditorily and visually presented words was 0.76 when the mean rating of each word was calculated over the ten subjects. The results show that for a large part, familiarity is basically the same whether a word is presented auditorily or visually. However, a significant number of words received quite different familiarity ratings, suggesting that the auditory mental lexicon and the visual mental lexicon are organized differently to some extent. These differences, at least in part, could be attributed to the idiosyncratic properties of Japanese orthography. The experiment will be continued using more subjects to obtain more reliable databases.

ISSN:0001-4966    

DOI:10.1121/1.408803

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Research has demonstrated that object names are given distinct prosodic status in child‐directed speech (Messer, 1981). Yet, the name most likely to attract infants is their own. Using the headturn preference procedure whether 4.5‐month‐olds prefer to listen to their own names was tested. Twenty‐four infants were presented with four names: their own, and three others. Foils were designed to investigate whether infants would false alarm to names with similar prosodic patterns (e.g., stress): One foil matched the stress pattern of the infants’ name; the other two followed the opposite pattern. Infants demonstrated significant listening preferences for their own names—even when compared to the foil with the same stress pattern. These findings provide the first evidence that infants as young as 4.5 months recognize their names. The findings also have some potentially important implications for lexical development. Perhaps the structure of infants’ early lexicons are influenced by their first lexical entries, i.e., their names. If so, this may explain individual differences often found in early lexical development—infants may be more likely to attend to words in the language environment that share a structural relation to their names. [Work supported by NICHD‐NIDCD.]

ISSN:0001-4966    

DOI:10.1121/1.408806

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

This study is a pilot investigation of how adult listeners spontaneously perceive the vowel quality in infant utterances. Recordings of two Japanese infants from the Tokyo area were used to generate the stimuli. One infant was recorded every week between 17 to 24 weeks of age. The other infant was recorded twice, at 32 and 78 weeks of age. The sessions lasted for about 1 h and included playing alone, playing with the mother, and eating. The stimuli for the perceptual evaluation were a random sample consisting of 57 utterances, drawn from the pool of noise and interference‐free utterances. Four phonetically trained subjects judged tongue height and frontness in a speeded judgment test paradigm. The results are compatible with the data from earlier acoustic studies [Davis and MacNeilage, J. Speech Hear. Res.33, 16–27 (1990)], using careful phonetic transcription. Japanese infants explore the opening dimension during the earlier period of babbling. Although the data cannot be used to establish the exact point at which front/back differentiation starts to occur, a significant difference was observed between the use of that dimension at 32 and at 78 weeks of age. [Research supported by The Bank of Sweden Tercentenary Foundation, Grant 90‐0150.]

ISSN:0001-4966    

DOI:10.1121/1.408764

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

The present study investigates infants’ sensitivity to word boundaries in fluent speech contexts. Using the headturn preference procedure, the first experiment demonstrated that 101/2‐month‐old American infants listened significantly longer to passages in which artificial 1‐s pauses were inserted at word boundaries, as opposed to between syllables within words. A second experiment examined the possibility that word‐stress patterns affect infants’ sensitivity to word boundaries in fluent speech. New groups of 101/2‐month‐olds were tested on new sets of passages. One group received passages with pauses at word boundaries or within words for words having a strong‐weak (SW) stress pattern. Another group received similarly arranged passages but the pauses involved words having a weak‐strong (WS) pattern. If infants use the onsets of strong syllables as cues to word onsets, they might be expected to prefer between‐word pauses in the SW passages but within‐word pauses in the WS passages, In fact, in both cases infants listened significantly longer to passages with between‐word pauses. These results suggest that infants at this age may not rely heavily on word‐stress patterns in locating word boundaries in fluent speech. [Work supported by NICHD and NIDCD.]

ISSN:0001-4966    

DOI:10.1121/1.408766

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Propagation models in underwater acoustics usually incorporate surface scattering effects in an ad‐hoc manner that in most cases requires making severe approximations. In particular, to include surface scattering in a marching algorithm for sound propagation in a coherent manner posses a difficult problem. Dozier [J. Acoust. Soc. Am.75, 1415–1432 (1984)] introduced a novel and rigorous approach to include surface scattering in the framework of the split‐step parabolic equation method. In this work the technique developed by Dozier is adapted and implemented in the realm of the finite element parabolic equation (FEPE) acoustic propagation model developed by Collins [J. Acoust. Soc. Am.86, 1097 (1989)]. The technique is tested by applying it to scattering from a sinusoidal patch as well as from a rough surface patch defined by a Pierson–Moskowitz spectrum. These results are compared against highly accurate solutions to the surface scattering integral equation (method of moments). [Work supported by ONR.]

ISSN:0001-4966    

DOI:10.1121/1.408770

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

In acoustic wave scattering from rough surfaces at low grazing angles the usual approximations are known to break down. In the forward‐scattering regime this case is often treated by the parabolic integral equation method. The scattering of plane waves within this formulation is considered, and effective reflection coefficients are derived for slightly rough surfaces. Of the higher‐order statistics, the dependence of the diffuse and specular components upon incident angle is also examined. The problem of surface reconstruction can be expressed in terms of coupled integral equations; it is explained how in the parabolic case these are easily treated. A major problem, however, is backscatter; a nonparabolic approach to this problem for low‐grazing angles is described. [Work supported by Smith Institute Research Fellowship.]

ISSN:0001-4966    

DOI:10.1121/1.408776

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Enhanced low‐frequency scattering levels from a single fish at its swimbladder resonance and a frequency invariant return for an octave or so above have been predicted by simple monopole scattering models [Love (1977)]. These characteristics have also been measured, more or less, with fish schools [McCartney (1967)]. In this talk the ‘‘more or less’’ is explored by modeling the school as a number of monopole scatterers quasi‐randomly distributed within an ellipsoidal volume, with and without mutual scattering taken into account. The swimbladder natural frequencies themselves are also taken to be random with a uniform PDF over a finite band. For a given realization, overall returns are computed in both the frequency and time domains. Computed fluctuations in aspect are compared with those for a Gaussian amplitude distribution. The influence of mutual scattering is shown as a function of the mean free path among individual fish. Finally, it is noted that though swimbladder gas volume and bulk modulus indicate aP5/6hydrostatic pressure dependence, swimbladder natural frequencies typically vary asP1/2[Weston (1967)]. [Work sponsored by Naval Undersea Warfare Center, New London Detachment.]

ISSN:0001-4966    

DOI:10.1121/1.408780

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

The theoretical investigation of scattering underwater sound waves by algae has been performed. The dependencies of sound level in the reflection waves upon parameters of the algae (sizes, biomass) are determined. For this purpose physical models corresponding to the typical kinds of the algae are developed. Scattering of sound by the algae are considered as the diffraction of the sound wave on the random set of the three‐dimensional curved elastic bodies. By solving Helmholtz equation for the definite boundary conditions on the surface of the bodies, sound pressure in the waves scattered by the acoustic semi‐transparent curved plates and rods corresponding to the plates and stems of the algae are computed. The obtained results can be used for the development of hydroacoustic methods of investigation of the continental shelf and also for reconnaissance of the algae abundance.

ISSN:0001-4966    

DOI:10.1121/1.408736

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP