• Journal of Broadcast Engineering
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• v.17 no.6
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• pp.1061-1068
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• 2012

This paper deals with a noise reduction algorithm which uses the binary masking approach in the time-frequency domain to improve speech intelligibility. In the binary masking approach, the noise-corrupted speech is decomposed into time-frequency units. Noise-dominant time-frequency units are removed by setting the corresponding binary masks as "0"s and target-dominant units are retained untouched by assigning mask "1"s. We propose a binary mask estimation by comparing the local signal-to-noise ratio (SNR) to a threshold. The local SNR is estimated by a training-based approach. An optimal threshold is proposed, which is obtained from observing the distribution of the training database. The proposed method is evaluated by normal-hearing subjects and the intelligibility scores are computed by counting the number of words correctly recognized.

• Journal of Biomedical Engineering Research
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• v.22 no.3
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• pp.241-247
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• 2001

ABR(auditory brainstem response) is one of the audiometry which measures objective hearing threshold level by acquiring electric evoked potentials emanated from auditory nerve system responding to an auditory stimulation. However, the obtained potentials which are largely interfered by power line noise, have extremely low SNR, thus ensemble average algorithm is generally used. The purpose of this study was to investigate the effect of iteration number in ensemble average on the reduction of the power line noise. The power line noise was modeled to be a 60 Hz sinusoidal signal and the energy of the modeled signal was calculated when it was averaged. It was verified by simulation that the energy had the periodic zero points for each stimulation rate, and 60 Hz signal induced by the power line was applied to the developed ABR system to confirm that the period of zero energy point was the same with that of the simulation. By the properly selected iteration number, power line noise could be reduced and more reliable ABR could be acquired.

• Explosives and Blasting
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• v.28 no.2
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• pp.119-132
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• 2010

There are many dispute with a construction due to such environment problem as vibration and noise. Generally, we have a standard for acceptance level in land. But we have not a sufficient standard for acceptance level or guide line in underwater sound. In other countries, a acceptance level or guide line in underwater sound has been suggested. Especially the management criterion of underwater noise for fish has bee suggested using the measurement data (peak pressure, rms, energy and SEL) by a hydrophone. In Korea, there is no management criterion of underwater noise for fish. This study suggested the management criteria of underwater noise for fish based on the measured data by a hydrophone.

• Journal of Information Technology Services
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• v.10 no.2
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• pp.259-269
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• 2011

The B$\'{e}$k$\'{e}$sy audiometer is used to determine not only hearing threshold but also assumption of recruit phenomenon and cause of disease. However, current B$\'{e}$k$\'{e}$sy audiometer takes an operational model, so called face-to-face model, in which model one audiometrist can assess only one subject at a time. As a result, the face-to-face model leads to high audiometrist's labor cost and long waiting time when there exist many subjects. To improve such weakness, this paper extends PC based B$\'{e}$k$\'{e}$sy audiometer to support client/server model in which model one audiometrist enables to concurrently access several subjects. As providing capabilities such as real-time transfer of assessment result, video monitoring of subject and video chat, the same effect as face-to-face model but overcomes weakness of face-to-face model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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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.

• Journal of Biomedical Engineering Research
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• v.16 no.4
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• pp.471-480
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• 1995

The modification of Nl -N2 Audiograms before and after loudtone exposure onto the tympanic membrane of guinea pigs was examined. The exposure was a loud continuous tone of 106 dB SPL intensity at 10 KHz for 10 minutes. The comparison between Wl-H2 Audiograms pre and post loudtone exposure indicates that the exposed cochlea permanently lost its normal hearing function. The largest threshold shifts wore found between 12-13.2KHz. The functional change of the cochlea after the loudtone exposure depends on the state of the cochlea before the trauma. More sensitive cochlea is more critically damaged in its function after the trauma than less sensitive cochlea.

• The Journal of the Acoustical Society of Korea
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• v.41 no.1
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• pp.58-63
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• 2022

This study was conducted to examine the characteristics of pitch perception and temporal resolution through Within-/Cross-Channel Gap Detection Thresholds (WC/CC GDTs) using low-frequency pure tones (such as 264 Hz, 373 Hz and 528 Hz related to C4, C4#, and C5 musical tones. 40 young people and 20 elderly people with normal hearing participated in this study. The results of WC GDTs were approximately 2 ms ~ 4 ms threshold values regardless of frequencies in two groups. There was no statistically significant difference in WC GDTs between groups. In both groups, CC GDTs were larger than WC GDTs, and as the frequency difference increased, the CC GDTs also increased. In particular, in the comparison between groups of CC GDTs, the results of the elderly group were 8 times ~ 10 times larger than that of the young group, and there was a statistically significant difference between the groups. These data also showed a different trend of GDTs in comparison with the previous data obtained from musical stimuli.This study suggests that GDTs may influence pitch perception mechanisms and can be used as psychoacoustic evidence for nonlinear responses of auditory nervous system.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.3
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• pp.89-93
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• 2009

Purpose: To purpose of this study was the pure-tone audimetry changes to compare pre and post fogging after visual correction in normally hearing adults. Methods: The estimated that no ocular and audiolar disesases, we selected (male: 30, female: 20) in corrected visual acuity over the 1.0 eye. Pre and post fogging were measured using the pure-tone audimetry. Results: To compared fre and post fogging, fre fogging was higher than fre fogging. The take value were just about every kind of Hz but 200 Hz, respectively which were statistically significant (p<.05). Low Hz area in 250 and 500 Hz were 6.8${\pm}$8.4dBHL, 4.3${\pm}$6.6dBHL, there is not all the difference between any other area, 2000 Hz in the middle Hz area was 0.8${\pm}$4.5dBHL. Conclusions: The study presents different results of measurements in within normal limits. we thought that pure-tone thresholds to the pre and post fogging after refractive correction in normal adults and would be used basic data.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.8 no.2
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• pp.95-99
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• 2014

Binaural interaction can recognize the same intensity sound by stimulating two ears alternatively, and it can be record auditory brainstem responses (ABR). However, We needs to be researched about binaural interaction in asymmetric binaural acoustic stimulation. 17 normal young hearing university students were participated. Clicks were presented at the intensity of 90 dB nHL to one ear and the click intensity was increased from 0 to 90 dB nHL with a separation of 10 dB to another ear, simultaneous. BI waveform was obtained by subtracting the sum of the asymmetrically evoked potentials from the binaurally evoked potentials; i.e. BI = B - (L + R). Latency and amplitude was measured 'peak to following trough' of IV-V complex of BI waveform. Threshold of BIC (t-BIC) was obtained using amplitude depend on stimulus intensities (paired sample t-test). Latency shifted in 4.65, 4.63, 4.57, 4.58, 4.62, 4.6, 4.48, 4.36, 4.23 ms for peak, 5.57, 5.51, 5.51, 5.59, 5.61, 5.55, 5.44, 5.28, 5.19 ms for trough, and amplitude shifted in .0.32, -0.3, -0.34, -0.32, -0.42, -0.53, -0.54, -0.61, $-0.67{\mu}V$ from 0 to 90 dB nHL in every 10 dB, respectively. t-BIC was observed 40 dB nHL(p=.001).

• Journal of Veterinary Clinics
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• v.37 no.3
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• pp.123-129
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• 2020

We aimed to investigate the differences in the efficacy of insert and circumaural earphones when performing the brainstem auditory evoked response (BAER) test with dogs. Hearing loss may occur congenitally or secondarily in dogs. The BAER test, unlike the classical ethological method, is the most reliable diagnostic tool to assess canine auditory function. Furthermore, there are certain advantages of using insert earphones rather than the standard, circumaural earphones. We subjected eight dogs to the BAER test with insert earphones and circumaural earphones. The result revealed that the latency of waves was delayed with an insert earphone. The inter-peak latency did not show any significant differences between the two transducers, and the threshold was higher when using an insert earphone. Moreover, the circumaural headphones produced a greater degree of crossover effect than the insert earphones, and this cross-over effect could affect the outcomes of the BAER test. Considering these results, we concluded that insert earphones may be more appropriate when performing the canine BAER test.