Sungmin Koo

Improvement of Noise Control System at Workplace with High Level Noise

Improvement of Noise Control System at Workplace with High Level Noise Sungmin Koo, Jinsook Kim and Dukhwan Lim Graduate Program in Audiology, Section of Audiology and Speech Pathology and Research Institute, Hallym University, Chuncheon, Korea High level noise at workplace results in noise-induced hearing loss (NIHL). It was determined by World Healthe Organization (WHO) that the NIHL be the most fifteenth most serious problem found in adults and could derive individual social isolation and national economic burden. Domestic workplace noise also have been increased showing the highest exceeding rate out of several harmful factors during 1995-2000. NIHL, tinnitus and various other problems. It is necessary to equip various adminstration programs for preserving worker’s health from high level noise at workplace. The purpose of this study was to propose an tentative plan of domestic noise labeling and noise control application model. After searching the advanced country’s noise labeling system, actual condition of noise existence at workplace, and noise control system for the working environment and the noise generating instruments, the following two methods were proposed. One was a tentative plan of domestic noise labeling indicating noise quantification of frequency weighting, the rate of noise generation including the range of noise level, and diagrammed spectrum of the noise. The other was noise control application model that can measure the noise at the real working place, analyze the characteristics of noise, and developing the noise managing program with finding and controling noise causing instruments, effective noise measuring steps, and hearing conservation program. We can expect better working place with the successful noise labeling and controling system.

Effects of Binaural Masking Level Difference on Discrimination “Gom” and “Gong” Under Various Filtered Noises and SNRs

Effects of Binaural Masking Level Difference on Discrimination “Gom” and “Gong” Under Various Filtered Noises and SNRs Sungmin Koo, Eunok Kim, Doohwan Chung and Dukhwan Lim Graduate School, Hallym University, Chuncheon, Korea Division of General Studies, Choongang University, Seoul, Korea Bokeum Hearing Aids, Seoul, Korea Section of Audiology, Audiology & Speech Pathology Research Institute, Hallym University, Chuncheon, Korea The purpose of this study was to investigate the effects of filtered noises in discriminating “Gom /Gong” under the given SNR conditions and to identify the contributions from BMLD with various phase conditions trough the revised analysis on the current data set. The results showed that the effects of the low pass filtered noise at 1 kHz cutoff frequency on word discrimination was statistically significant at the SNR level of -10 dB (paired-t test, df=9, t=2.168, 1-tailed, p<0.05). Further studies should focus on detailed mechanisms of filtered noises and BMLD in word discrimination to provide useful information in developing speech signal processing of assistive listening devices.

Suppression of DPOAE with Various Noise Bands under Contralateral Stimulation in Normal Hearing Adults

Suppression of DPOAE with Various Noise Bands under Contralateral Stimulation in Normal Hearing Adults Hyun-Kyung Jang, Sungmin Koo, Sungeun Kim and Dukhwan Lim Graduate Program in Audiology, Hallym University, Chuncheon, ENT, Seoul National University, Seoul, Section of Audiology and Audiology & Speech Pathology Research Institute, Hallym University, Chuncheon, Korea Distortion product otoacoustic emission (DPOAE) amplitudes and latencies were measured in response to contralateral stimuli of noises with different spectral bands to examine the effects of noise bands on efferent suppression in 26 normally hearing adults. Four types of contralateral noise stimuli were white noise, 2 kHz low pass filtered noise, 2-4 kHz band pass filtered noise, and 4 kHz high pass filtered noise. The DPOAE amplitudes were measured at the f2 range of 1.0, 1.3, 1.6, 2.0, 2.5, 3.2, 4.0, 5.0, 6.3 kHz and DPOAE latencies were measured at the f2 range of 1, 3, 6 kHz without contralateral stimulation and with contralateral stimulation of 60 dB. DPOAE amplitudes exhibited suppressive effects mainly on the mid frequency region of 1 to 2 kHz. White noise was more effective in suppressing DPOAEs than filtered noises were. The new measures of response interactions among noise bands also showed strong non-linear responses in lower frequecy range of DPOAE (1-2 kHz). In this experiment, contralateral masking did not appear to affect latencies of DPOAE since latencies of DPOAE showed no statistcally significant differences under contralateral noise stimulations (p>0.05).

Hearing aid Modification for Problematic Occlusion：Case Report

Hearing aid Modification for Problematic Occlusion:Case Report Sung-Min Koo, Keuyng-Won Lee, Dukhwan Lim and Jung-Hak Lee Graduate Program in Audiology, Section of Audiology, Audiology and Speech Pathology, Department of Otolaryngology, Hallym University, Chuncheon, Korea One of the common complaints from persons with hearing aids is occlusion effect (OE). OE is mainly caused by the enhancement of low-frequency components of a sound and this problematic occlusion could be reduced through decreasing low-frequency gains or modifying the size/length of the vent. Since vents are not always with uniform lengths or diameters, audiologists need to understand various interrelated factors such as vent sizes and hearing aid gains based on patterns of hearing loss. This article reports the cases where OE problems were managed through modified vents with simple self-questionnaires.

Effects of Relative Phases on Discrimination of Harmonic Complex Tones

Effects of Relative Phases on Discrimination of Harmonic Complex Tones Sungmin Koo and Dukhwan Lim 1 Graduate School, Hallym University, Chuncheon, Korea, 2 Division of Speech Pathology & Audiology, Research Institute of Audiology & Speech Pathology, Hallym University, Chuncheon, Korea The effects of relative phases on discriminating harmonic complex tones were studied under no noise conditions for twelve young adults with normal hearing. Harmonic complex tones consisted of the first 4 harmonics of 500 Hz with equal amplitudes and initial starting phases of 0°. Stimuli were digitally synthesized and two alternative forced choice (2AFC) method was used to collect the corresponding discrimination scores. Results showed that the clear symmetry around 180°phase shift except for 2000 Hz. The higher percentage of correct discrimination was noticed as well at around the phase shift of 180°. These discrimination scores were significantly influenced by the variation of the phase shift of the third harmonic component of the complex signal regardless of the amount of phase shifts except at 5°and 315°. Data suggested that the phase shifts of individual harmonic tones had differential contributions to the discrimination of tonal complex tones. Further studies of phase effects on harmonic complex tones under various conditions would be helpful in analyzing the behavioral responses to harmonic stimuli.