• The Journal of the Acoustical Society of Korea
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• v.26 no.8
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• pp.403-408
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• 2007

In a large corpus-based speech synthesizer, a break, which is a parameter influencing the naturalness and intelligibility, is used as an important feature during a unit selection process. Japanese is a language having intonations, which ate indicated by the relative differences in pitch heights and the APs(Accentual Phrases) are placed according to the changes of the accents while a break occurs on a boundary of the APs. Although a break can be predicted by using J-ToBI(Japanese-Tones and Break Indices), which is a rule-based or statistical approach, it is very difficult to predict a break exactly due to the flexibility. Therefore, in this paper, a method is to conduct a unit search by dividing breaks into two types, such as a fixed break and a flexible break, in order to use the advantages of a large-scale corpus, which includes various types of prosodies. As a result of an experiment, the proposed unit selection method contributed itself to enhance the naturalness of synthesized speeches.

• Journal of Korean Association for Spatial Structures
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• v.11 no.1
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• pp.67-75
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• 2011

The present work investigate the effect of sound reinforcement systems on the acoustics of a large dome stadium using a computer simulation. The acoustics of a dome stadium was predicted analyzed by varying room absorption, as well as the configuration of speakers including their directivity, installed height, and numbers. It was found that both D50 and RASTI were improved by increasing room absorption. Larger EDTs were observed according to the increase of room absorption at mid and high frequencies. On the other hand, RT did not show any significant correlation with the changes in room absorption, which might be the effect of a forced linear fitting for non -linear energy decay process. With respect to the speaker configuration, the speech intelligibility of a sound reforcement system installed at higher placed more relied upon their directivity rather than room absorption, Also, lower placing of speakers was found to be effective in decreasing RTs regardless of room absorption.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.4 s.121
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• pp.342-349
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• 2007

Following the 2002 World-Cup held in Korea, studies have been actively conducted on plans to utilize all-weather stadiums of fine figures, where large-scale spaces are available for various utilizations. In Japan, dome-type stadiums have been built and are utilizing across the whole nation not only for sports events but also variety of other large-scale events. PTFE(poly tetra fluoro ethylene) is one of the membrane material mainly used for the outer ceiling surface of membrane structures. However, there has not been enough research on the acoustical properties of PTFE membrane material which has been widely used in the multi-purpose stadiums. In this study, air permeability values and sound absorption coefficient of PTFE membrane materials were measured and evaluated in the gymnasium. From the results of measurements of sound absorption coefficient and air permeability of inner membrane materials, it was found that the sound absorption coefficient was good in the air permeability range of $5{\sim}15\;cc/cm^2/s$. Also the relation ship between air permeability and sound absorption coefficient was very high and the sound absorption coefficient was the highest in the range of $6{\sim}9\;cc/cm^2/s$. Secondly, an analysis on the measurements sound absorption characteristics of inner membrane material reveals that the overall sound absorption coefficient was stabilized(higher than 0.5 throughout the whole frequency bands) when the air space behind the membrane material was deeper than 600 mm. When PTFE sound absorptive membrane material was installed in the ceiling of gymnasium, it was confirmed that sound absorptive membrane material can reduce reverberation and increase speech intelligibility in the gymnasium.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2
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• pp.113-122
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• 1995

This paper describes characteristics of a bone conduction telephone which was developed for conductive hearing impaired persons to call without additional devices and results of its performance test. Not only the hearing impaired but also normal hearing persons can use this telephone because we developed a bone conduction vibrator with which they can perceive speech signal using functions of air conductive hearing as well as bone conductive hearing. It also has tone control function compensating hearing losses for the hearing impaired originating from their hearing characteristics, and using this function together with received volume control it has received volume range of 20dB in loudness rating, which is similar effect as what a telephone set with built-in received amplifier has. From results of articulation and intelligibility tests for 19 hearing impaired persons, we can see that if their bone-conduction hearing loss is 61dB or less, they can understand words or sentences and response well with this telephone.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.9 no.2
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• pp.121-128
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• 2015

In this paper, we introduce our smart phone application for hearing impaired people. Unlike previous hearing aids application, our application has both functions of self hearing tests and sound amplification. We provide user with two types of self hearing test, those are standard hearing test and detail hearing test. Each test has different advantages like short test time and accurate test result, however both tests provide reliable result. Our hearing test allows that user can measure their hearing loss level according to the frequency. Sound amplification function provide proper fitting formula by using NAL-NL1, and it guarantees high speech intelligibility. Our application can also memorize user's fitting data at specific test condition. Therefore those who using our hearing aids application can easily reset their hearing aids / earphone properties periodically. Our application is advanced at the aspect of self fitting function that no other previous application did. So we are expecting these comfortable processes about fitting lead the number of hearing aids user to be increased.

• The Journal of the Acoustical Society of Korea
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• v.33 no.5
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• pp.316-325
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• 2014

The basic unit of school is a classroom and the aural environment of the classrooms is essential factor for education purposes. Therefore, many efforts have been undertaken for enhancing the acoustical performance of the classrooms in many countries. As a result, acoustic criteria including reverberation time and background noise level have been established in US and UK for school classrooms depending on the usage and size of the rooms. However, in Korea, there has been little researches concerning the room acoustical investigations of the classrooms. The present study investigates the current situation of the aural environment of the 15 classrooms in Korea including elementary, middle and high schools. The acoustic criteria measured include RT, $D_{50}$, STI, SNR and background noise level. As the results, it was found that the background noise levels of the schools adjacent to roads exceed the US and UK standard of 35 dB(A). Also, most schools have so low SNR that they may be interfered by noise, which may affect speech transmission. It was also revealed that some schools have longer RT than the US standard of 0.6 s, but they all have high speech intelligibility.

• Journal of Korean Association for Spatial Structures
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• v.7 no.5
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• pp.75-82
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• 2007

The present work measured and analyzed changes in the acoustics of a sound field which has a retractable ceiling. An 1/20 scale model of an openable space was built and measurement was carried out by varying the opened area of a ceiling. The most widely used room acoustic and design parameters, RT, EDT, and D50 were investigated. The results suggest that the use of RT as an acoustic design parameter may not be proper in an openable space and further it is likely to mislead the initial acoustic design of such spaces. It is mainly due to the characteristics of RT in which non-exponential decay processes are linearly fitted. Early decay times were found to be decreased in proportion to increaing the ratio of opened area. D50, an index of speech intelligibility, was effectively shows the influence of openings on the acoustics. It is also found that EDT and D50 at the seats, not directly exposed to the opened part of a ceiling, were almost linearly decreased in proportion to the ratio of opened area, while little influence was found for the opening ratio larger than 40% at the directly exposed seats to the opened part of a ceiling.