• 말소리와 음성과학
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• 제6권2호
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• pp.73-79
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• 2014

Alveolar fricative sounds /s/ and /s'/ are learned last for normal children in the speech development process for Koreans. These are especially difficult to articulate for hearing-impaired children often causing articulation errors. The acoustic phonetic evaluation uses testing tools to provide indirect and object information. These objective resources can be compared with standardized resources on speech when interpreting the results of a test. However, most previous studies in Korea did not consider acoustic studies that used the spectrum moment values of hearing-impaired children. Therefore, this study was conducted to compare the characteristics of hearing-impaired children's pronunciation of fricative sounds using spectrum moment values. For this purpose, the study selected a total of 10 hearing-impaired children (5 boys and 5 girls) currently in 3rd or 5th grade and attending one of the elementary schools in Seoul or Gyeonggi-do. For the selection process, their age, type of hearing aid, implantation of hearing aid (CI) before two years of age, hearing capacity (dB) before and after wearing the hearing aid, duration of speech rehabilitation, and time of learning alveolar fricative sounds were all considered. Also, 10 normal children (5 boys and 5 girls) were selected among 3rd or 5th grade students attending one of the elementary schools in Seoul or Gyeonggi-do. The subjects were asked to read the carrier sentence, "I say _______," including a list of 12 meaningless syllables composed of CV and VCV syllables, including alveolar fricative sounds /s/ and /s'/ and vowels /a/, /i/, and /u/. The recorded resources were processed through the Time-frequency Analysis Software Program to measure M1 (mean), M2 (variance), M3 (skewness), and M4 (kurtosis) of the fricative noise. No significant differences were found when comparing spectrum threshold values in the acoustic phonetic characteristics of hearing-impaired children and normal children in alveolar fricative sound pronunciation according to vowels /a/, /i/, and /u/, alveolar fricative sounds /s/ and /s'/, and syllable structure (CV, VCV) other than, for M3 in the comparison of groups according to disability. In the comparison of syllable structures, there were statistically significant differences in M1, M2, M3, and M4 with clinical significance. However, there was no significant difference in results when comparing the alveolar fricative sounds according to the vowels.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1482-1489
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• 2007

In this paper, characteristics of infrasound and low-frequency noise emission from large modern wind turbines are experimentally investigated. The sound measurement procedures of IEC 61400-11 and ISO 7196 are utilized to field test and evaluation of noise emission from each of 1.5 MW and 660 kW wind turbines using the stall regulation and the pitch control for the power regulation, respectively. It was found that the G-weighted SPLs of low-frequency noise including infrasound shows positive correlation with the wind speeds, irrespective of methods of power regulation. This highlights the potential complaint of local community against the infrasound and low-frequency noise of wind turbines. The comparison of measured data with the existing hearing thresholds and criteria curves shows that it is highly probable that the low-frequency noise from the 1.5 MW and 660 kW wind turbines in the frequency range over 30 Hz leads to the psychological complaint of ordinary adults, and that the infrasound in the frequency range from 5 Hz to 8 Hz causes the complaint by rattling the house fitting such as doors and windows.

• 한국소음진동공학회논문집
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• 제17권8호
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• pp.736-740
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• 2007

A laboratory study on low frequency noise assessment has been carried out to evaluate the relevance of the weighting curve. Especially, the A-weighting curve which is used in most noise assessments has been evaluated using the acceptability limit in this study. The acceptability limit is one of the indicators in which the subjective responses were well-reflected. For the measurement of the acceptability limit, pure tone stimuli were used in the frequency range between 20 and 200 Hz. The measurement was proceeded in the anechoic chamber to minimize the background noise level. A total of 29 test subjects, who were aged between 19 to 33 years, participated in this study. They had been exposed to various stimuli for about 1 hour by supra-aural earphone. The measurement consisted of two listening sessions: hearing threshold and the acceptability limit session. The results showed that the tendency of the acceptability limit curve was approximately equal to C-weighting curve which had been found to be superior to A-weighting curve in assessment of low frequencies.

• 대한의용생체공학회:의공학회지
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• 제34권1호
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• pp.24-33
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• 2013

To enhance the speech perception of hearing aid users in noisy environment, most hearing aid devices adopt various beamforming algorithms such as the first-order differential microphone (DM1) and the two-stage directional microphone (DM2) algorithms that maintain sounds from the direction of the interlocutor and reduce the ambient sounds from the other directions. However, these conventional algorithms represent poor directionality ability in low frequency area. Therefore, to enhance the speech perception of hearing aid uses in low frequency range, our group had suggested a fractional delay subtraction and integration (FDSI) algorithm and estimated its theoretical performance using computer simulation in previous article. In this study, we performed a KEMAR test in non-reverberant room that compares the performance of DM1, DM2, broadband beamforming (BBF), and proposed FDSI algorithms using several objective indices such as a signal-to-noise ratio (SNR) improvement, a segmental SNR (seg-SNR) improvement, a perceptual evaluation of speech quality (PESQ), and an Itakura-Saito measure (IS). Experimental results showed that the performance of the FDSI algorithm was -3.26-7.16 dB in SNR improvement, -1.94-5.41 dB in segSNR improvement, 1.49-2.79 in PESQ, and 0.79-3.59 in IS, which demonstrated that the FDSI algorithm showed the highest improvement of SNR and segSNR, and the lowest IS. We believe that the proposed FDSI algorithm has a potential as a beamformer for digital hearing aid devices.

• 음성과학
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• 제3권
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• pp.26-37
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• 1998

The Connected Speech Test (CST) was developed to test hearing aid performance using realistic stimuli (Connected speech) presented in a background of noise with a visible speaker. The CST has not been investigated as a measure of speech reading ability using the visual portion of the CST only. Thirty subjects were administered the 48 test lists of the CST using visual presentation mode only. Statistically significant differences were found between the 48 test lists and between the 12 passages of the CST (48 passages divided into 12 groups of 4 lists which were averaged.). No significant differences were found between male and female subjects; however, in all but one case, females scored better than males. No significant differences were found between students in communication disorders and students in other departments. Intra- and inter-subject variability across test lists and passages was high. Suggestions for further research include changing the scoring of the CST to be more contextually based and changing the speaker for the CST.

• 한국산업보건학회지
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• 제15권3호
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• pp.277-281
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• 2005

Air-line mask is an important personal protective equipment for workers working under hazardous surroundings in which a fixed ventilation system is difficult to be installed. If the air-line mask make loud noise, works wearing the mask may be faced with health problems such as noise induced hearing loss(NIHL). The purpose of this study is to introduce a low noisy technology for workers using air-line mask. A traditional type air-line has been improved to an advanced air-line mask with lesser noise. In the mask, air suppling conduits consists of multi tubes are placed inside of the front of the safety helmet. The noise level reduced from 80dB(A) to less than 80dB(A) when measured by KS A 0701 method at Center for Safety Inspection, Testing and Certification for KOSHA. It is suitable for related regulation[Article 35 of the Industrial Safety and Health Act(Test of Personal Protective Equipment)]. While workers working in noise level of over 90dB(A), they may expose to 82dB(A) or less when they wear the advanced masks. This type masks can be an alternative for works suffering from loud noise generated by traditional air-line masks.

• 한국산업보건학회지
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• 제30권4호
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• pp.387-393
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• 2020

Objective: This study aimed to investigate the differences in temporary threshold shift (TTS) and recovery patterns according to different types of sound and volume. Methods: TTS and recovery patterns were assessed for eight students after 30-minute exposure to both 70.0 dB and 90.0 dB of factory noise (noise) as well as music. TTS was measured before exposure and two minutes post exposure, and recovery patterns were evaluated every 10 minutes for one hour. The subjects performed activities of daily life and sleeping times as usual but taking drugs or drinking alcohol were prohibited. The experiment was repeated three times with an interval of at least 16 hours. ANOVA and T-test were carried out using SPSS 19.0 for Windows. Results: The hearing threshold of all subjects before exposure was less than 30 dB at all frequencies. Mean TTSs of 70 dB noise and 90 dB noise exposure were 0.14 and 4.48 dB (p<0.001). Meanwhile, the difference in music was insignificant (-0.63 dB and 0.55 dB, p=0.063). A significance in the difference was also found between the mean TTS of music and noise exposure, more obviously at 90.0 dB (p<0.001) than at 70 dB (p=0.232). The TTS differences were found frequency-wise in terms of sound type. Mean TTS by frequency was higher at 4,000 and 6,000 Hz than at other frequencies, and higher in noise than music at the same sound pressure. The TTS difference in each frequency between both sound types was significant at 90 dB (p<0.001). Subjects mostly recovered from TTS in one hour after exposure, but not with 90 dB-noise exposure. Conclusion: TTS and recovery patterns were different depending on the sound type. When exposed to factory noise, TTS was greater and recovery time was longer compared to music at the same sound pressure. These results suggested that the difference in cognitive processes and psychological factors according to the type of sound causes a change in TTS and recovery.

• 한국환경교육학회지:환경교육
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• 제20권3호
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• pp.18-30
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• 2007

This study was concentrated on the development of the effective noise environmental education program(NEEP) for elementary student. And through this program, the student who is remaining as a spector or has not active attitude for noise problems will be encouraged to solve the troubles spontaneously. The object of this study was the two classes in H elementary school where is near to the Daegu international airport. One class that is a group for experiment has five NEEP lessons during five weeks in the time for the creative discretional activities. The other class, which was compared with the experimental group was given no lessons. NEEP was made on the bases that are the contents related with noise in 7th elementary education policy and the data developed by previous researchers. This program is containing basic concepts for noise and the effects of noise problems on human body or studying in class. And after using NEEP, students became more sensitive for noise environments than previous. And also students showed the positive attitude for solving noise troubles. It was meaningful in the level of p<.001 that the result of noise knowledge and awareness in the pre-post test within experiment group. However, all of the results in comparison group didn't represent statistically meaningful difference. And there were meaningful differences between experiment and comparison group after carrying out NEEP. In the area of noise knowledge and awareness, there were clearly meaningful results in the level of p<.001. Although the difference in noise attitude was a little, it was analyzed to have not a meaningful result. What suggested for researches in future are as follows. First, because until now the concrete research for the elementary student who exposed to noise and experienced a difficulty in hearing is deficient, many studies are needed. Second, NEEP with more lessons is required because the change of effective attitude needs long term. Third, due to the student who exposed to noise generally has low ability for concentration, NEEP compensated with activities is needed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1379-1382
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• 2006

Recently, the method of the apartment building design has been changed from wall type structures to moment structures. With like this reason dry walls are used plentifully. Especially, the gypsum board was used from previously plentifully however the weak point of it is difficult to maintain because it weak strength. For the improvement of gypsum board, light weight concrete panel using cement board is used recently. As this study is the research of the series t on the development of non-hearing light weight concrete Panel using bottom ash, the Purpose of this study is to obtain basic data for application in the field. The results are that the structure 1 satisfies domestic standard concerned with sound insulation between households at the laboratory and field test.

• 한국소음진동공학회논문집
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• 제16권9호
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• pp.897-903
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• 2006

The reduction of the vehicle interior noise has been the main interest of noise and vibration harshness (NVH) engineers. The driver's perception on the vehicle noise is affected largely by psychoacoustic characteristic of the noise as well as the SPL. In particular, the heating, ventilation and air conditioning (HVAC) system sound among the vehicle interior noise has been reflected sensitively in psychoacoustics view point. Even though the HVAC noise is not louder than overall noise level, it clearly affects subjective perception to drivers in the way of making to be nervous or annoyed. Therefore, these days a vehicle engineer takes aim at developing sound quality as well as reduction of noise. In this paper, we acquired noises in the HVAC from many vehicles. Through the objective and subjective sound quality (SQ) evaluation with acquiring noises recorded by the vehicle HVAC system, the simple and multiple regression models were obtained for the subjective evaluation 'Pleasant' using the semantic differential method (SDM). The regression procedure also allows you to produce diagnostic statistics to evaluate the regression estimates including appropriation and accuracy. Furthermore, the neural network (NN) model were obtained using three inputs(loudness, sharpness and roughness) of the SQ metrics and one output(subjective 'Pleasant'). Because human's perception is very complex and hard to estimate their pattern, we used NN model. The estimated models were compared with correlations between output indexes of SQ and hearing test results for verification data 'Pleasant'. As a result of application of the SQ indexes, the NN model was shown with the largest correlation of SQ indexes and we found possibilities to predict the SQ metrics.