• Proceedings of the KSME Conference
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• 2001.11b
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• pp.682-687
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• 2001

This study represents effect of exhaust performance by according to active muffler valve spring. The experimental parameter were divided engine speed and torsion coil spring constant. The sound pressure level was generally low at engine speed 2000-2500rpm but That was showed the lowest at spring constant k=0.75. Flow speed of exhaust gas was showed the fast at spring constant k=0.75 but the low value was showed at k=0.97. It was contained a rather low concentration of carbon monoxide(CO) at engine speed 2000-2500rpm and k=0.81, low concentration of hydrocarbon(HC) at spring constant k=0.81 but that was high at spring constant k=0.97. A conclusion based on FFT analysis was generally low concentration value at k=0.79 and k=0.81. The temperature distributions into the muffler was shown similar conditions. Heat transfer was well spreaded at thermocouple No.8 because valve was opened.

• The Journal of the Acoustical Society of Korea
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• v.23 no.6
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• pp.437-445
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• 2004

In this paper. we describe a novel method for transforming audio contents according to user's preference on sound field. Sound field effect technologies. which transform or simulate acoustic environments as user's preference, are very important for enlarging the reality of acoustic scene. However huge amount of computational power is required to process sound field effect in real time. so it is hard to implement this functionality at the portable audio devices such as MP3 player. In this paper, we propose an efficient method for providing sound field effect to audio contents independent of terminal's computational power through processing this functionality at the server using user's sound field preference, which is transfered from terminal side. To describe sound field preference, user can use perceptual acoustic parameters as well as the URI address of room impulse response signal. In addition, a novel fast convolution method is presented to implement a sound field effect engine as a result of convoluting with a room impulse response signal at the realtime application. and verified to be applicable to real-time applications through experiments. To verify the evidence of benefit of proposed method we performed two subjective listening tests about sound field descrimitive ability and preference on sound field processed sounds. The results showed that the proposed sound field preference can be applicable to the public.

• The Journal of the Acoustical Society of Korea
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• v.21 no.8
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• pp.708-718
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• 2002

In this paper, the problems in identifying the noise sources by using the sound intensity technique are dealt with for the general radiated near-field from vibro-acoustic sources. For this purpose, a three-dimensional model structure resembling the engine room of a car or heavy equipment is considered. Similar to the practical situations, the model contains many mutually coherent and incoherent noise sources distributed on the complicated surfaces. The sources are located on the narrow, connected, reflecting planes constructed with rigid boxes, of which a small clearance exists between the whole box structure and the reflecting bottom. The acoustic boundary element method is employed to calculate the acoustic intensity at the near-field surfaces and interior spaces. The effects of relative source phases, frequencies, and locations are investigated, from which the results are illustrated by the contour map, vector plot, and energy streamlines. It is clearly observed that the application of sound intensity technique to the reactive or reverberant field, e.g., scanning over the upper engine room as is usually practiced, can yield the detection of fake sources. For the precise result for such a field, the field reactivity should be checked a priori and the proper effort should be directed to reduce or improve the reactivity of sound field.

• Journal of Digital Contents Society
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• v.11 no.2
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• pp.235-242
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• 2010

Differently from instruments which synthesized sounds and tones in the past, voice synthesis engine for music production has reached to the level of creating music as if actual artists were singing. It uses the samples of human voices naturally connected to the different levels of phoneme within the frequency range. Voice synthesis engine is not simply limited to the music production but it is changing cultural paradigm through the second creations of new music type including character music concerts, media productions, albums, and mobile services. Currently, voice synthesis engine technology makes it possible that users input pitch, lyrics, and musical expression parameters through the score editor and they mix and connect voice samples brought from the database to sing. New music types derived from such a development of computer music has sparked a big impact culturally. Accordingly, this paper attempts to examine the specific case studies and the synthesis technologies for users to understand the voice synthesis engine more easily, and it will contribute to their variety of music production.

• Journal of Biosystems Engineering
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• v.31 no.1 s.114
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• pp.1-8
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• 2006

This study was conducted to identify the characteristics of PTO rattle noise of a direct engine-PTO driveline for agricultural tractors. In order to reduce production costs of agricultural tractors, a direct engine-PTO driveline was recently introduced to the tractors produced in Korea. This simplified drive line reduced a number of gears and counter shafts in previous one. However, it caused a severe rattle noise under an idle condition, which was perceived as intolerable by many tractor operators. PTO rattle noise was measured at two locations: one 3 em apart radially from the centerline of the PTO shaft and another 100 em apart backward from the PTO end and 160 em high from the ground. Characteristics of the rattle was analyzed using the data measured near the PTO shaft. It was found that the period of rattle noise was same as the explosion stroke of engine and its peak level was about 123 dB (A) with PTO engaged at an idle engine speed of 880 rpm. As the engine speed increased, the rattle noise decreased. The frequency band of the rattle was 0.5-2.0 kHz and the frequency of peak sound pressure was 1.4 kHz. When compared the rattle noise between the locally produced and imported tractors of the same type of PTO driveline, the former generated louder rattle noise than the imported one by 7 dB (A). It was suggested that the rattle noise of local tractors must be reduced at least by 7 dB (A) to meet the international level.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.6
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• pp.1443-1453
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• 1998

This paper presents the speech synthesis engine that converts the character strings kept in a computer memory into the synthesized speech sounds with enhancing the intelligibility and the naturalness by adapting the waveform processing method. The speech engine using demisyllable speech segments receives command streams for pitch modification, duration and energy control. The command based engine isolates the high level processing of text normalization, letter-to-sound and the lexical analysis and the low level processing of signal filtering and pitch processing. The TTS(Text-to-Speech) system implemented by using the speech synthesis engine has three independent object modules of the Text-Normalizer, the Commander and the said Speech Synthesis Engine those of which are easily replaced by other compatible modules. The architecture separating the high level and the low level processing has the advantage of the expandibility and the portability because of the mix-and-match nature.

• Journal of Korea Multimedia Society
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• v.7 no.10
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• pp.1464-1477
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• 2004

Recently, there is a growing consideration that game authoring tools can play an important role in producing 3D games. In this paper, we introduce our 3D game authoring tool. The tool consists of a map editor, a sound editor, a game data exporter/previewer, and a special effect editor. This tool can help a game designer Produce game data such as game maps, sound effects, and special effects, and so on. In this paper, we implemented a prototype game content to verify the effectiveness of the developed authoring tool.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.9
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• pp.857-862
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• 2013

Recently, the importance of GDI and diesel engine noise reduction is required, so newly designed components very close to noise sources are added in order to maximize the sound absorbing performances. In this study, the high temperature resistant part made with meta-Aramid nonwoven, which was applicable for high temperature applications of about $200^{\circ}C$ or more, such as engines and exhaust systems, was developed. And three-dimensional shaped component was successfully fabricated, and it was observed high temperature resistance of $260^{\circ}C$, lightweight properties and the noise was decreased by 1.0 dB with 70 g of product.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.251-257
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• 1998

Active mufflers have been mainly applied in the large industrial engine due to considerable expense for implementation, but a necessity of development has been increased by the tightened regulation of exhaust noise and the request of high power. In this study, the active muffler prototype for installing in an automobile is designed and constructed. The active muffler is designed so that the primary noise and the control sound are propagated as a plane wave in the outlet. Therefore, the error microphone could be placed outside the high temperature centers of the tail pipe, and the noise radiating to the outside could be reduced in the whole areas around the outlet. For evaluating the control performance of the prototype, the control experiments of band-pass filtered random signal and the modulation of sinusoidal signal which are generated from the primary noise speaker as practical exhaust sound level are implemented. And to investigate the radiation pattern from the outlet of tail pipe and the noise reduction level of points placed adjacent to the outlet, the sound level of adjacent points of thirty is measured.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.69-74
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• 2006

It is known that the various noise sources which are engine, transmission, tire, intake system, etc exist at vehicle driving status. Specially noises which cannot be expected by a driver induce unpleasantness to all passengers. These noises are difficult to distinguish noise sources or specifications because of too many vehicle parts. Therefore in this paper, study on abnormal noise of bush on suspension system is performed by the measurement and analysis of the noises of bushings that are generated artificially. The measured noises are analyzed by two points-view of spectrum and sound quality. Finally, it is shown that the noise sources of bushings on the suspension system which are the pillow ball joint bush of a control arm and the rubber bush of a lower arm could be distinguished by the spectrum distribution and a index value based on tonality.