No abstract available.
Acoustics*

No abstract available.
Acoustics*

PURPOSE: The number of the repatriated Korean students who had overseas study at early ages is increasing. They received foreign education, they can speak international languages, but they have many difficulties in articulation and intonation of the Korean language. This study aims to measure closure and aspiration duration, length of consonants, length of subsequent vowels, and ratio of consonants against subsequent vowels in vowel-consonant-vowel (VCV) syllables. METHODS: This study compares the acoustic and phonetic characteristics of repatriated and native students, the ratio of articulation error of Korean plosives, the closure and aspiration duration, and the ratio of the aspiration duration against the closure duration. RESULTS: The ratio of articulation error of Korean plosives between repatriated and native students is 19% and 2%, respectively. The closure duration was significantly longer in repatriated students than in native students. The aspiration duration was significantly longer in repatriated students than in native students. No difference was found in the ratio of aspiration duration against closure duration between the native and repatriated students. CONCLUSION: This study can be a good reference for estimating the phonetic difficulties of Korean elementary students who had overseas study at early ages.
Acoustics ; Humans

No abstract available.
Acoustics* ; Voice*

No abstract available.
Acoustics* ; Dysarthria*

OBJECTIVES: Various problems are encountered during audiometric testing. Deviation from reference threshold levels for supra-aural earphones is often a serious problem when hearing levels are measured. This paper reports the acoustic calibration of clinical audiometers used for special periodic health examination. METHODS: ANSI S3.6-1996 Specification for Audiometers represents our most current and best resource for information regarding audiometers. The acoustic calibration was measured in 211 clinical audiometers and compared with the ANSI S3.6-1996 reference threshold levels for supra-aural earphones. RESULTS: Among 211 clinical audiometers, 56 (26.5%) exceeded the permitted deviation from reference threshold levels at any test frequency in ANSI S3.6-1996 for left supra-aural earphones, and 54 (25.6%) for right. An exhaustive calibration was required for 16 audiometers (7.6%) in both supra-aural earphones. The absolute difference in dB deviation from reference threshold levels by performed acoustic calibration at least annually were statistically significant at any test frequency (p<.05). CONCLUSIONS: The results of this study strongly indicate that clinical audiometry is being conducted with pure-tone audiometers having unallowable sound pressure levels deviations for supra-aural earphones. The validity of audiometric hearing thresholds are significantly affected by these deviations from the acoustic calibration levels of audiometers. Therefore audiometer calibration need to be checked functionally daily and acoustically at least annually.
Acoustics* ; Audiometry ; Calibration* ; Hearing

No abstract available.
Acoustic Stimulation* ; Acoustics*

Hidden Markov model (HMM) is known to be one of the most powerful methods in the acoustic modeling of heart sound signals. Conventionally, we usually use a fixed number of states for each HMM. However, due to the various types of the heart sound signals, it seems that more accurate acoustic modeling is possible by varying the number of states in the HMM depending on the signal types to be modeled. In this paper, we propose to assign different number of states to the HMM for better acoustic modeling and consequently, improving the classification performance of the heart sound signals. Compared with when fixing the number of states, the proposed approach has shown some performance improvement in the classification experiments on various types of heart sound signals.
Acoustics ; Heart ; Heart Sounds

The objective evaluation of velopharyngeal closure function is the key to diagnosis and therapy control of velopharyngeal incompetency. The aim of this study is to evaluate the aerodynamic and acoustic characteristics of the velopharyngeal closure function of patients who have developed velopharyngeal incompetency after management with speech aids. The test words were composed of sustained vowels /a/, /i/, /e/, /u/, /ja/, /je/, /wi/ and polysyllabic words /p'ap'i/, /siso/, /mami/ for measuring nasalance, The data was collected before the placement of the speech aids and one to three months after. The results were as follows:The nasalance score of the velopharyngeal incompetency speakers was higher than that of the normal control group, except for nasal sounds, and was decreased after placement of the speech aids, especially in high vowels /i/ (P<.01) and /wi/ (P<.05).
Acoustics ; Diagnosis ; Humans

Magnetoacoustic tomography (MAT) has some advantages such as high sensitivity and high spatial resolution. The generating mechanism of acoustic source is the research foundation of forward and inverse problems. A coustic signals were respectively simulated by using monopole and dipole radiation theory in the experimental conditions, then the differences between their acoustic pressures were discussed, and furthermore the contrast and validation were conducted by physical experiments in this study. The physical experimental results showed that acoustic waveform of MAT had a certain directivity and therefore they indicated that dipole model showed higher approximation to the real facts than monopole model. It can be well concluded that this research has cardinal significance for the accurate algorithm of MAT.
Acoustics ; Algorithms ; Tomography ; methods