• The Journal of the Acoustical Society of Korea
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• v.28 no.2E
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• pp.60-65
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• 2009

The present study aims to investigate the effects of sound diffusers and absorbers on the sound clarity in classrooms. In order to do this, computer simulations were carried out to find the effective area of treatment which could enhance the sound clarity in the room. Acoustic measurements were undertaken in a lecture room with several conditions changing the surface of walls and ceilings with diffusers and absorbers. Diffusion and absorption treatments were applied to the side walls, rear wall and the ceiling of the classroom. SPL, RT, D50, RASTI were measured at 9 measurement points with one sound source and MLS was used as the sound source signal. The results show that higher sound clarity was obtained when diffusers were applied to rear walls and ceiling rather than side walls. Also, it was confirmed that absorption increased sound clarity more effectively with smaller amount in comparison with diffusers. It was also concluded that the effects of sound diffusers and absorbers on the sound clarity could be obtained distinctly at the rear area of the classroom.

• The Journal of the Acoustical Society of Korea
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• v.31 no.3
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• pp.129-141
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• 2012

The present study aims to investigates the effects of the physical sound clarity (D50, STI) on the subjective speech intelligibility of the both Korean and Chinese languages which can be caused by increase of the sound absorption in classroom. In order to this, sound measurements were undertaken at a classroom with and without absorption materials. Also, speech intelligibility tests were conducted by Korean and Chinese students using their native languages. As the results, it was found that both sound clarity and speech intelligibility were improved with increasing sound absorption. Also, it was revealed that Chinese speech intelligibility was more improved than Korean with same impose of sound absorption. It was considered by the difference of phonetic characteristics of two languages. Analysing correlation of physical sound clarity and subjective speech intelligibility, it was shown that D50 is highly correlated with Korean (0.696) and Chinese (0.707) respectively. Also, STI was highly correlated with Korean (0.651) and Chinese (0.665). Thus, it can be concluded that D50 and STI have significant correlations with the speech intelligibility.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.228-229
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• 2008

In this study, we propose an effective method to improve the clarity and period of the beat in a ring structure. Ring is an simplified model of a Korean bell, in which beating vibration and sound are very important features. An equivalent ring theory is applied and finite element analysis on the equivalent ring is performed to determine the condition of the asymmetric element for the clear and proper period beat. The clarity and the period of the beat are improved by attacking asymmetric mass and decreasing local thickness. Using the equivalent ring, the amount and position of the local variation for the required beat condition are determined and the results are verified by experiment.

• The Journal of the Acoustical Society of Korea
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• v.34 no.2
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• pp.146-156
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• 2015

This study investigated how the location of sound absorptive materials and sound diffusers affects the acoustic performance of small auditoriums. It was conducted for a standard model established with the averaged dimension of 36 auditoriums which had opened since 2000 in Daehak-ro, Seoul. In this study, the installation area of finishing materials was calculated upon a back wall which had the smallest installation effective area of finishing materials. To analyze the changes of acoustic performance according to installation location of finishing materials, experiments were carried out using the 1/10 down scale models for 8 cases which were made by classifying the installation location of ceiling and side wall into the front, middle and rear part.The used acoustic parameters were reverberation time (RT), early decay time (EDT), clarity (C80), definition (D50) and speech transmission index (STI). In result, the index related to the amount of reverberant sound (RT, EDT) showed the great changes when evaluating it through just noticeable difference (JND), but the one related to clarity (C80, D50, STI) hardly indicated the changes. In case to obtain short reverberation time, it was most effective to control reverberation time through the side walls when installing sound absorptive and diffusive materials, and side wall front was the location which could get the shortest reverberation time.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2378-2387
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• 2017

Violinists learn to make better sounds by hearing and evaluating their own playing though numerous practice. This study proposes a new method of auditory feedback, which mimics this violinists' step and verifies its efficiency using experiments. Making the desired sound quality of a violin is difficult without auditory feedback even though an expert violinist plays. An algorithm for controlling a robot arm of violin playing robot is determined based on correlations with bowing speed, bowing force, and sound point that determine the sound quality of a violin. The bowing speed is estimated by the control command of the robot arm, where the bowing force and the sound point are recognized by using a two-axis load cell and a photo interrupter, respectively. To improve the sound quality of a violin playing robot, the sounds information is obtained by auditory feedback system applied Short Time Fourier Transform (STFT) to the sounds from a violin. This study suggests Gaussian-Harmonic-Quality (GHQ) uses sounds' clarity, accuracy, and harmonic structure in order to decide sound quality, objectively. Through the experiments, the auditory feedback system improved the performance quality by the robot accordingly, changing the bowing speed, bowing force, and sound point and determining the quality of robot sounds by GHQ sound quality evaluation system.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2003.11a
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• pp.59-65
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• 2003

The present article has the purpose of evaluating subjective response of Won Buddhism sanctums by psychoacoustics experiment. Furthermore, basing on this experiment, the present article makes a suggestion of a physical sound-evaluating index. To achieve the purpose, I conducted an psychoacoustics experiment at 6 sanctuaries out of the representing 40 sanctuaries of Won Buddhism sanctums, which size is bigger than 1,000 m$^3$. I made a reanalysis with 3 Buddhist sanctums out of the subjects of psychoacoustics experiment which are generally rated superior. From the result, I can make each evaluation type into two types, sound clarity and space sense of sound. Also, I make various suggestions of physical parameter, with which I can evaluate the proper sound condition for Won Buddhism sanctums.

• Imaging Science in Dentistry
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• v.34 no.3
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• pp.145-150
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• 2004

Purpose: To compare three digital radiographic imaging sensors by evaluating the visibility of endodontic file tips with interobserver reproducibility and assessing subjectively the clarity of images in comparison with the x-ray film images. Materials and Methods: Forty-five extracted sound premolars were used for this study. Fifteen plaster blocks were made with three premolars each and #8, 10, 15 K-flexofiles were inserted into the root canal of premolars. They were radiographically exposed using periapical x-ray films (Kodak Insight Dental film, Eastmann Kodak company, Rochester, USA), Digora imaging plates (Soredex-Orion Co., Helsinki, Finland), CDX 2000HQ sensors (Biomedisys Co., Seoul, Korea), and CDR sensors (Schick Inc., Long Island, USA). The visibility of endodontic files was evaluated with interobserver reproducibility, which was calculated as the standard deviations of X, Y coordinates of endodontic file tips measured on digital images by three oral and maxillofacial radiologists. The clarity of images was assessed subjectively using 3 grades, i.e. plus, equal, and minus in comparison with the conventional x-ray film images. Results: Interobserver reproducibility of endodontic file tips was the highest in CDR sensor (p < 0.05) only except at Y coordinates of #15 file. In the subjective assessment of the image clarity, the plus grade was the most frequent in CDR sensor at all size of endodontic file (p < 0.05). Conclusion : CDR sensor was the most superior to the other sensors, CDX 2000HQ sensor and Digora imaging plate in the evaluation of interobserver reproducibility of endodontic file tip and subjective assessment of image clarity.

• Journal of the Korean Institute of Educational Facilities
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• v.11 no.1
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• pp.5-14
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• 2004

Since 1990s in Korea, elementary school classrooms have been designed toward open education system in pursuit of variety of educational purpose. Also, the architectural designs of schools have been acomplished for individual school not based on the standard design code. The present paper aims to investigate the acoustic environment of existing classrooms and to compare the sound insulation capacity between the ordinary classrooms and the newly built classrooms for open education. The current acoustical situation of elementary classrooms was analyzed using field measurements and questionnaire survey. In order to this, Three elementary schools were selected which were built in 1978, 1996 and 2000 respectively. Room acoustical parameters including Reverberation time(RT), Definition(D50), Speech Intelligibility(RASTI), Transmission loss(TL) and STC were measured in a classroom in each elementary school classroom. Each measurement was undertaken with the windows and doors being open or closed. As the result, it was found that the transmission loss between rooms in open classrooms is, $5{\sim}6dB$ in average, inferior than the ordinary classrooms. The RASTI of 0.70 was measured in newly built classrooms which is better than old classrooms(0.70) and open classrooms(0.73). This was shown as same in the speech definition measurements. This results from the condition of sealing and airtightness of classrooms and floor materials. The results denote that open classrooms have poor acoustic condition in sound insulation and speech intelligibility.

• Fire Science and Engineering
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• v.32 no.4
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• pp.42-49
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• 2018

In this study, in order to investigate whether or not the emergency broadcasting sound generated from an emergency broadcasting speaker is clearly transmitted to the occupant through architectural sound simulation, when the loudspeaker for emergency broadcasting is installed at intervals of 25 m according to NFSC 202 for a rectangular hallway. The sound pressure level and speech intelligibility index were analyzed according to changes in building finishing materials. With a reflective material finishing, sound pressure level satisfied the standard while speech intelligibility index was low. As a result of applying the sound absorbing material finishing, clarity and speech transmission index was improved to a level that could be understood by the occupant, whereas the sound pressure level delivered to the occupant decreased in the same space.

• Proceedings of the Acoustical Society of Korea Conference
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• 1992.06a
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• pp.3-8
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• 1992

The theory of subjective preference with temporal and spatial factors which include sound signals arriving at both ears is described. Then, auditory evoked potentials which may relate to a primitive subjective response namely subjective preference are discussed. According to such fundamental phenomena, a workable model of human auditory-brain system is proposed. For eample, important subjective attributes, such as loudness, coloration, threshold of preception of a reflection and echo distrubance as well as subjective preference in relation to the initial time delay gap between the direct sound and the first reflection, and the subsequent reverberation time are well described by the autocorrelation function of source signals. Speech clarity, subjective diffuseness as well as subjective preference are related to the magnitude of inter-aural crosscorrelation function (IACC). Even the caktail party effects may be eplained by spatialization of human brain, i.e., independence of temporal and spatial factors.