• The Journal of the Acoustical Society of Korea
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• v.34 no.3
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• pp.184-191
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• 2015

In this paper, a normal mode reverberation model for a range-independent environment of shallow water is proposed to calculate the reverberation level in the low-frequency range. Normal mode is used to calculate the acoustic energy propagating from the source to the scattering area and from the scattering area to the receiver. Each mode is decomposed into up and down going waves to consider scattering strength at the scattering area. The scattering functional form combines Lambert's law with a Gaussian-like term near the specular direction based on Kirchhoff approximation considering bottom condition. For verification of the suggested model, the result is relatively compared to several solutions of the problem XI and XV in the Reverberation Modeling Workshop I sponsored by the US Office of Naval Research.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.4
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• pp.619-627
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• 2015

This paper presents a speech enhancement method using non-negative matrix factorization (NMF). In the training phase, each basis matrix of source signal is obtained from a proper database, and these basis matrices are utilized for the source separation. In this case, the performance of speech enhancement relies heavily on the basis matrix. The proposed method for which speech basis matrix is made a high reconstruction error for noise signal shows a better performance than the standard NMF which basis matrix is trained independently. For comparison, we propose another method, and evaluate one of previous method. In the experiment result, the performance is evaluated by perceptual evaluation speech quality and signal to distortion ratio, and the proposed method outperformed the other methods.

• The Journal of the Acoustical Society of Korea
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• v.36 no.1
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• pp.12-22
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• 2017

It is important to predict accurately reverberation level, which is a limiting factor in underwater target detection. Recently, the studies have been expanded from monostatic sonar to bistatic sonar in which source and receivers are separated. To simulate the bistatic reverberation level, the computation processes for propagation, scattering strength, and scattering cross section are different from those in monostatic case and more complex computation processes are required. Although there have been many researches for bistatic reverberation, few studies have assessed the bistatic scattering cross section which is a key factor in simulate reverberation level. In this paper, a new method to estimate the bistatic scattering cross section is suggested, which uses the area of intersection between two circles. Finally, the reverberation levels simulated with the scattering cross section estimated using the method suggested in this paper are compared with those estimated using the methods previously suggested and those measured from an acoustic measurements conducted in May 2013.

• Journal of Music and Human Behavior
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• v.14 no.1
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• pp.41-62
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• 2017

The purpose of this study was to examine the effect that preferred music listening had on police officers' occupational stress and fatigue. The musical intervention took place over a total of six sessions from October 11 to October 19, 2016. At each session, the experimental group (n = 19) received 20 minutes of music listening with individually customized playlists that were compiled based on their preferred music list. The control group (n = 21) simply took a break from work for 20 minutes. Every participant checked his or her occupational stress and fatigue level before and after the experiment using the Occupational Stress Inventory and Subjective Symptoms of Fatigue Test. The data were then analyzed by the SPSS 22.0 statistics program. To examine the homogeneity and pretest-posttest results between groups, an independent t test was conducted, and a paired t test was used to examine the pretest-posttest results within groups. The results confirmed all hypotheses. Findings support that the use of preferred music listening is an effective way to help police officers to control their occupational stress and fatigue. This study used a convenience sample and has limited generalizability. Future research should explore interactive approaches in music therapy as well as receptive music listening for alleviating police officers' occupational stress and fatigue.

• 재활복지
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• v.20 no.1
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• pp.113-130
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• 2016

The purpose of this study is to determine the effects of guided imagery activities using music on both mood states and physiological responses of psychiatric inpatients. The experimental group was consisted of 27 psychiatric patients participating in the guided imagery activities using music for 11 minutes. Also, the control group was formed with 27 psychiatric patients with non-musical intervention. Mood states, blood pressure, pulse and skin temperature were checked before and after session. We could see the significant difference in the score of five areas-tension, depression, anger, vigor, fatigue-showed most differences in score. Also, the score of skin temperature of both experimental group and between two groups showed significant differences, too. Therefore, we can conclude that these results were showing that guided imagery activities using music was an effective nursing intervention method for altering mood state of psychiatric patients. Besides, it seemed to have physiological impact to make patients relax tension backed up by change of skin temperature.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.603-620
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• 2021

A land nodal seismic system was employed to acquire seismic reflection data using stand-alone cable-free receivers in a land-river area. Acquiring reliable data using this technology is very cost effective, as it avoids topographic problems in the deployment and collection of receivers. The land nodal airgun system deployed on the mouth of the Hyungsan River (in Pohang, Gyeongsangbuk Province) used airgun sources in the river and receivers on the riverbank, with subparallel source and receiver lines, approximately 120 m-spaced. Seismic data collected on the riverbank are characterized by a low signal-to-noise (S/N) and inconsistent reflection events. Most of the events are represented by hyperbola in the field records, including direct waves, guided waves, air waves, and Scholte surface waves, in contrast to the straight lines in the data collected conventionally where source and receiver lines are coincident. The processing strategy included enhancing the signal behind the low-frequency large-amplitude noise with a cascaded application of bandpass and f-k filters for the attenuation of air waves. Static time delays caused by the cross-offset distance between sources and receivers are corrected, with a focus on mapping the shallow reflections obscured by guided wave and air wave noise. A new time-distance equation and curve for direct and air waves are suggested for the correction of the static time delay caused by the cross-offset between source and receiver. Investigation of the minimum cross-offset gathers shows well-aligned shallow reflections around 200 ms after time-shift correction. This time-delay static correction based on the direct wave is found essential to improving the data from parallel source and receiver lines. Data acquisition and processing strategies developed in this study for land nodal airgun seismic systems will be readily applicable to seismic data from land-sea areas when high-resolution signal data becomes available in the future for investigation of shallow gas reservoirs, faults, and engineering designs for the development of coastal areas.