• Phonetics and Speech Sciences
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• v.11 no.4
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• pp.35-43
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• 2019

This study examines the voice onset times (VOTs) of Korean stops produced by Korean learners of English with high language proficiency and long L2 exposure (i.e., Korean-English bilinguals) to assess whether the VOTs of their lax and aspirated stops are merging and, if so, which types of stops are being changed. Thirteen Korean speakers (six female and seven male) who had studied in the USA for more than three to ten years participated. The results show that the speakers in this study with long L2 exposure are participating in the VOT merger, in which VOTs for aspirated stops are reduced while those for lax stops are increased. In other words, change in VOT affects not only aspirated stops but also lax stops. The results indicate that L1 phonetic drift may not be primarily affected by the amount of L2 exposure, and language contact may not be the primary factor triggering a sound change in the Korean stop system. Further study is necessary focusing on the phonetic shift of the "lax" category because it may play a pivotal role in a tonogenetic-like sound change in present-day Korean.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.9 no.1
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• pp.27-31
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• 1998

Nasal sounds include nasalized vowels and consonants. Nasal cavity is important for the acoustics of nasal sounds. Evaluating the effects of site-specific nasal obstruction on nasal sound will help us to understand the importance of nasal geometry for the nasal sound and to foretell voice change after nasal surgery This study was designed to analyze the change of nasality and formant characteristics of nasal sound by obstructing different sites around the ostiomeatal unit(OMU). Ten adult male and female volunteers participated. The nasal formants and bandwidths of nasal consonant /n/ were checked in various conditions of nasal obstruction. The nasalance of rabbit, baby, and mama passages were compared in each conditions. Nasalance of all passages decreased when anterior portion of OMU was obstructed. Center frequency of first nasal formant(NF1) of /n/ has decreased in the order of anterior, inferior obstruction. The bandwidth of NF1 decreased in female with anterior obstruction. Anterior portion of OMU is most critical to the change of nasality and acoustics of nasal consonant. When anterior portion of OMU is obstructed, the shift of NF1 to a lower frequency and the narrowing of NF1 bandwidth are the major acoustic changes of nasal consonant /n/.

• Journal of Preventive Medicine and Public Health
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• v.10 no.1
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• pp.94-101
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• 1977

Noise pollution, both in the environment and in the workplace, has been recognized as a major health hazard -one that can impair not only a person's hearing but also his physical and mental well-being. As industrialization progresses, the prevalence rate of occupational diseases is increasing, especially hearing loss, which has the highest prevalence rate among the occupational diseases. The major cause of noise is the construction of various large industries without any regulation of noise sources. Therefor, we must establish an enactment to control mechanical noise sources. as soon as possible. For the purpose of controlling the noise source, we must have exact data about such things as the sound level, the frequency of the peak sound and the revolutions per minute (r.p.m.) of the machine (a measure of the power of its motor). This study was undertaken in order to define the noise characteristics, the power of the machine's motor, the change of the sound level and the peak sound as the r.p.m. increases, and the permissible exposure time. The sample size of this study was 74 machines at 11 plants in 6 industries. The results are as follows; 1. The breakdown of the types of mechanical noise noted was : 63.6% continuous normal sound, 26.9% intermittent sound, 4.7% continuous repeating sound and 4.6% impulsive sound. 2. With respect to the type of industry, the overall sound level was the highest in the mechanical industry, with $103.8{\pm}2.8dB(A)$, and lowest in the textile industry, with $89.2{\pm}1.43dB(A)$. 3. With respect to the type of machine, the highest sound level was 124 dB(A) caused by Gauzing(II), in the mechanical industry, and the lowest was 76 dB(A) caused by Attachment (Jup Chack) (I) in the timber industry. 4. The shortest permissible exposure time to Gauzing(II) in the mechanical industry was less than 15 minutes. 5. Among 74 machines, 68.2% of the peak sound was situated in the high frequency range (52.7% at 2 KHz, 4.1% at 4 KHz and 1.4% at 8 KHz). 41.8% of the peak sound was in the middle frequency range (4.1% at 250Hz, 14.8% at 500Hz and 22.9% at 1KHz). 6. If one machine had two motors or more, the peak sound was shifted to the low frequency range. 7. As the r.p.m. increased, the overall and peak sound levels were increased without any change of the frequency of the peak sound. 8. Whenever the machines had the same kind and the same r.p.m., the overall and peak sounds were changed by the physicochemical characteristics of the raw materials and the management.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.274-281
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• 2013

Field measurement method of heavy/soft impact sound pressure level which is regulated in JIS and ISO has been using in Korea, Japan and Canada. It is reported that heavy/soft impact sound pressure level was varied by the sound field condition of receiving room such as sound absorption power and room volume. In this study, it is checked that heavy/soft impact sound pressure level was affected by the receiving sound field condition. Rubber ball and bang machine sound pressure level was measured in the vertically connected reverberation chamber. In oder to check the effect of receiving sound field on heavy/soft impact sound pressure, sound absorption power was changed with polyester sound absorption blankets with air space and glass wool. The reverberation time at 1 kHz band was changed from 10 s to 0.2 s by sound absorption material. Rubber ball sound pressure level measured without sound absorption material was 58 dB in $L_{i,Fmax,AW}$, but the level was 46 dB with sound absorption treatment. From this result, it is confirmed that sound field correction method is needed in the heavy/soft impact sound pressure level measurement method using bang machine and rubber ball.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.156-159
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• 2002

This study reports on physical properties of the noise radiation caused by expansion of exhaust gas and vibration of pumps according to change of vaccum degree. The fundamental responses show that the sound power level radiated is proportional to the common logarithm of the degree of vaccum.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.304-307
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• 2004

To reduce the structure-born sound by floor impact source in an apartment building, it is necessary to identify the relationship between floor impact sound and vibration. Various impact sources which were made by a bang machine and an impact ball were used for measurement of impact sound and vibration. The experimental results show that the linear relationship between floor impact sound and vibration was in existence despite of various floor impact sources.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.222-228
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• 1999

The two-microphone sound-intensity technique has been used for the detection of defects in radially loaded ball bearings. The difference in the sound-intensity levels measured for bearings with no defect and for those with intentionally introduced defects of different sizes in their elements under various operating conditions of loads and speeds is demonstrated. A change in the intensity frequency spectrum because of the defects is observed. The results show that the detectability of an outer-race defect is much better than that of on inner-race or ball defect. It is difficult to detect defects at lower speeds. Sound-pressure measurements were also performed fur comparison, and it is shown that the detectability of defects by sound-intensity measurements is better than that by sound-pressure measurements.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.135-138
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• 2005

On the basis of theoretical studies on the effect of the cylinders attached to semi-infinite screens, the effect of the tangential sound power-transport along the cylindrical top section of noise barriers is studied. Four types of acoustical mechanism between the surface of the cylinder and the adjacent air particles are investigated, namely Z $\rightarrow$ $\infty$, Z $\rightarrow$ pc, Z $\rightarrow$ 0 and actively controlled surface sound field. In active control case the sound power parallel to the surface of the attached cylinder is minimized by means of a secondary sound field, which is generated from a part of the attached cylinder. In each case the change in the acoustical shadow zone was shown and compared. The numerical study shows the possibility of deflecting the incident sound by minimizing the acoustical surface impedance of the upper sections.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.915-918
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• 2005

Acoustic holography uses Kirchhoff·Helmholtz integral equation and Green's function which satisfies Dirichlet boundary condition Applications of acoustic holography have been taken to the sound field neglecting the effect of flow. The uniform flow, however, changes sound field and the governing equation, Green's function and so on. Thus the conventional method of acoustic holography should be changed. In this research, one possibility to apply acoustic holography to the sound field with uniform flow is introduced through checking for the plane wave in a duct. Change of Green's function due to uniform flow and one method to derive modified form of Kirchhoff·Heimholtz integral is suggested for 1-dimensional sound field. Derivation results show that using Green's function satisfying Dirichlet boundary condition, we can predict sound pressure in a duct using boundary value.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.17 no.1
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• pp.14-16
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• 2006

Background and Objectives: The purpose of this study is to investigate the change of vocal tract length according to the level of the pitch by the singers. Materials and Methods: Fifteen tenors were asked to produce successive /a/ sound in G4(382Hz) for the head register, C3(131Hz) for the chest register and usual speaking sound. The control group consisted of 15 males of an similar age who are not professional singers. The length of vocal tract was calculated by applying the formula of Fn=(2n-1) c/4L(F : formant frequency, c : the speed of sound in the vocal tract(350m/sec), L : length of vocal tract, $n=1,2,3,4,{\ldots}{\infty}$). Results: In singer's group, there showed no significant statistical difference of length among head and chest register and usual speaking sound. However in the control group, there showed statistically significant difference of length. Comparison of the absolute difference in the length of vocal tract by changing level of pitch in phonation, between the control group and the singers group. Changing from G4 phonation to C3 phonation and C3 phonation to usual speaking sound showed statistically difference of vocal tract length was less in the singers group than the control group. Conclusion: The change of vocal tract length, in either speaking or singing, was less in singers than the control group. We could assume that the singers maintain their larynx position constantly throughout the pitch range when phonation.