• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.2
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• pp.146-153
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• 2014

This study investigates the effects of seat-design elements such as seating arrangement, shape, and height on speech privacy in high-speed trains. For the evaluation of speech privacy, acoustic simulation software was used to reproduce room acoustical conditions in passenger cars on the basis of in-situ measurement data. The influences of speech source directivity and source height on privacy distance ($r_P$) were investigated, and it was found that $r_P$ determined using an omni-directional source was relatively shorter than that determined using a directional source. It was also found that $r_P$ decreased when the source height was lower than the height of the seat-back because the seat-back blocked the propagation of speech from the sound source. The effect of seating arrangement was not significant when comparing the vis-a-vis seating and one-side seating arrangements. In addition, among the alternative seat-designs, the seats that block the space between the seats and cover the space near the ear were found to show significantly enhanced speech privacy in high-speed train passenger cars.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.332-339
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• 2007

As the economy has grown and the main industry in Korea has been changed from secondary industry to tertiary industry, the importance of indoor environment has been a matter of common concern, in which one of the main concerns is to improve the indoor acoustic conditions. However, even though this is required more than before, there are no measures to protect the human being from the noise of electric home appliances. This is owing to the absence of the data about sound power level of electric home appliances. So, we investigate the sound power level of them and analyze the acoustical characteristics of each one. First, we tried to investigate the sound power measurement method of each electric home appliance. After it we test the sound power level of them. From the survey, we can know that the vacuum cleaner is the most noisy electric home appliance, and the refrigerator is the least noisy one. The noise of a range hood is distributed over a wide range frequency. Lastly, we intented to propose the proper method measuring sound power level on each electric home appliance.

• KIEAE Journal
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• v.14 no.1
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• pp.83-89
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• 2014

The residents' demand for the comfortable life is promoting development of wall and window which has high sound insulation performance. To develop wall system, various aspects should be considered on the environment, material, construction and structure. Especially focusing on the acoustical view, the economical solution is one of the most critical point. Recently the interest on the partition wall is being increased, because it is useful for the Rahmen type apartment which is considered as an alternative to reduce floor impact sound. This study examines simplified measurement method of airborne sound insulation applied small size specimen, in order to save money to be used for the standard specimen then to promote the development process. The results showed that the simplified method could be effective for the wall system the sound insulation performance upto Rw 50 dB, and for the judgement of rank order of sound insulation performance of the similar wall type while developing.

• Speech Sciences
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• v.15 no.4
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• pp.19-27
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• 2008

Several studies on the pronunciation of English vowels point out that Korean learners have difficulty distinguishing English tense and lax vowel pairs. The acoustic comparisons of those studies are mostly based on the formant measurement at one time point of a given vowel section. However, the English lax vowels usually show dynamic changes across their syllable peaks and subjects' English levels account for various conflicting results. The purposes of this paper are to compare the temporal duration and dynamic formant tracks of English tense and lax vowel pairs produced by five Korean and five American males. The subjects were graduate students of an American state university. Results showed that both the Korean and American males produced the vowels with comparable durations. The duration of the front tense-lax vowel pair was longer than that of the back vowel pair. From the formant track comparisons, the American males produced the tense and lax pairs much more distinctly than the Korean male speakers. The results suggest that the Korean males should pay attention to the F1 and F2 movements, i.e., the jaw and tongue movements, in order to match those of the American males. Further studies are recommended on the auditorily acceptable ranges of F2 variation for the lax vowels.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.177-182
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• 2003

This study is directed toward determining the number and characteristics of psychologically meaningful perceptual dimensions required for assessing the sound Ouaiity with respect to vehicle interior and/or exterior noises. and toward identifying the acoustical or psychoacoustical bases underlying the perception. By nonmetric MDS and clustring analysis of sound quality data sets on our own, of critical importance are two perceptual dimensions for which subjective verdicts can be interpreted as loudness and sharpness. The perceptual dimensions based upon similarity judgments could be accounted for 48% and 24% of the variance. each of which might be a match for the acoustic parameter "A-weighted maximum pressure level"(r= .85) and for the psychoacoustic parameter "sharpness" (r= .65), respectively. On the other hand, the perceptual dimensions based upon preference ratings could explain 66% and 10% of the variance. where the acoustic parameter "A-weighted maximum pressure leve"(r= .92) might be taken to be a best predictor, but sharpness appeared to be less suitable for the description of Preference behavior. Linked to the results, the problems of quantitative modelling of subjective sound quality evaluation and also of implementing corresponding cognitive combination rule for technical and industrial applications, say having "winner-sound qualify" according to preference criteria will be shortly in discussion.

• ETRI Journal
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• v.31 no.6
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• pp.680-687
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• 2009

This paper reports on an improved piezoelectric microspeaker with a high sound pressure level of 90 dB, a total harmonic distortion of less than 15%, and coherence higher than 0.9. The fabricated Pb(Zr,Ti)$O_3$ (PZT) microspeakers have a thickness of only 1 mm including the speaker frame and an active area of 18 mm${\times}$20 mm. To achieve higher sound pressure and lower distortion, the PZT piezoelectric microspeaker has a well-designed speaker frame and a piezoelectric diaphragm consisting of a tilted PZT membrane and silicone buffer layer. From the simulation and measurement results, we confirmed that the silicon buffer layer can lower the first resonant frequency, which enhances the microspeaker's sound pressure at a low frequency range and can also reduce useless distortion generated by the harmonics. The fabricated PZT piezoelectric microspeakers are implemented on a multichannel speaker array system for personal acoustical space generation. The output sound pressure at a 30 cm distance away from the center of the speaker line array is 15 dB higher than the sound pressure at the neighboring region 30 degrees from the vertical axis.

• Speech Sciences
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• v.13 no.3
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• pp.133-149
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• 2006

This study attempted to compare acoustic parameters, physiological observation and perceptual evaluation values obtained from the treatment and control groups in order to find out which of the self voice feedback therapies was better and which methods to train them were more effective. The experimental group carried out various self voice feedback therapies while the control group did only vocal hygiene. The acoustic measurement and voice manipulation for providing the patients visual, auditory feedback were done by a speech analysis software, Praat. The authors designed vocal hygiene, abdominal respiration and Praat self voice feedback therapies and applied them to 15 patients while applying only one vocal hygiene to 15 of the control group. For the purpose of examining the degree of their voice improvement after the treatment, pre- mid- and final evaluations were made for the two groups at the beginning, the 6th week and immediately after the 8th treatment session. Results of this study were as follows: The treatment group showed much improvement after receiving the voice treatment. In particular, acoustical and physiological indices from the optical endoscopy, pitch variation(Jitter), amplitude variation (Shimmer), maximum phonation time(MPT), and psychoacoustic evaluation showed statistically significant improvements over the control groups.

• KIEAE Journal
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• v.9 no.1
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• pp.99-106
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• 2009

This study aims to survey the acoustical environment in the region around airport where there are various transportation noises such as aircraft noise, railway noise and traffic noise, and to analyze the subjective response on the noise to the people who live in house or work in office nearby airport. Measurement and subjective response evaluation were carried out at the same time and outdoor noise level was measured all day long to calculate one day results such as average Leq or one day WECPNL etc. The results showed that the military aircraft produces very high level comparing with commercial aircraft, for instance the sound level of commercial outdoor was lower than that of military aircraft indoor. Double and triple window were more effective for controlling the noise than single window, which showed the possibility of sound insulation treatment by installing windows having higher sound insulation performance. Finally the subjective response was resulted that the most annoying noise is from aircraft and counterplan they hope is 'airport moving out'. Leq 65 dB(A), the criteria value of sound insulation treatment, was corresponding to the subjective response of median annoyance '4' out of 7th scale.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1028-1031
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• 2004

Last target of architectural acoustics is that people wish to convey voice effectively from the space adaptively in use purpose in building. But, to how exactly through space sound source that wish to deliver from indoor can be passed does quantification sound estimation method is proposing various kinds physical parameter to estimate degree of voice definition (Speech articulation) and reverberation. Result that evaluate sound source about MLS signal and Impluse signal by pistol in this treatise could know that converge in MLS and measurement error extent about reverberation time(RT) of sound benevolent person. And value is thought there is problem showing change irregularly about sound benevolent person of D50, C80 etc. Finally, in case is spread sound field in difference of sound pressure level, when measure about change of sound pressure level, sound benevolent person could know that there is no different effect.

• The Journal of the Acoustical Society of Korea
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• v.35 no.3
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• pp.175-182
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• 2016

For application to several MHz photoacoustic imaging systems, a needle hydrophone was designed and fabricated by using PMN-PZT piezoelectric single crystal, and its characteristics were evaluated through comparison with a commercial PVDF(Polybinylidene Fluoride) hydrophone of which receiving sensitivity is known. The simulation using the KLM model results show that the peak receiving impulse response for $50{\Omega}$ terminating impedance of the fabricated hydrophone is -261.6 dB re $1V/{\mu}Pa$ and the frequency response is relatively flat over 2 ~ 12 MHz with fluctuation less than 5 dB. The measurement results using tone burst signals also show that it has higher (ave. 10.9 dB) sensitivity than the commercial hydrophone in 2 ~ 8 MHz, and the receiving sensitivity of $-255.8{\pm}2.8$ dB re $1V/{\mu}Pa$ was measured for the fabricated hydrophone. In addition, it is known that the photoacoustic signals and the image of a hair obtained by a mechanical scanned photoacoustic imaging system with the fabricated hydrophone were bigger and better than those obtained with the commercial hydrophone.