• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.930-935
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• 2001

The experimental characterization of hydrodynamic bearing spindle motor is performed for the practical implementation of high-performance hard disk drive system. Firstly, the design concept of hydrodynamic bearing for the disk drive system is addressed including the herringbone grooved journal bearing, the spiral grooved thrust bearing, capillary seal design, and the viscous pumping of fluid. Secondly, the experimental evaluation is performed for the disk drive system in which the hydrodynamic bearing spindle motor is implemented and its dynamic performances are compared with conventional ball-bearing spindle motor. The key parameters include NRRO(Non Repeatable Run-Out), disk dynamics, acoustics, and resultant PES (Position Error Signal). Finally, the external gyro-exciting test results including 200k CSS(Continuous Start-Stop) on three angular attitudes(0,90, 180 degree) are presented in order to verify the practical reliability of disk drive system subject to the gyro-motion of hydrodynamic bearing spindle motor.

• 한국소음진동공학회논문집
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• 제17권8호
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• pp.708-719
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• 2007

In case of indoor gymnastics training floor, in view of its characteristics, since it is simultaneously required the related smooth communication between the coach and the player, also the acoustic performance regarding to the clearness of music, besides the sport activity, the consideration about the acoustic character has entered the stage as an indispensable element. On such viewpoint, recently constructed dome-typed gymnastic training floor was optimized acoustic design with remodeling through acoustic simulation test. And acoustic satisfaction degree and reaction was attempted to investigate about the gymnastics training floor estimating value of human's psychological(sensual) degree using auralization that enables to experience the virtual sound field at the stage of design. As the result of investigation about the research on the space of object, it could be known that the valuation regarding to the acoustic performance of 'after-improvement' was distinctly more refined than that of 'before-improvement'. It is now considering that such result of the study can be utilized as the useful data which enables to improve the retrenchment effect of the construction cost as well as the acoustic capability, by means of the prediction control on the acoustic problem from the stage of design, for the occasion when the similar indoor sport gymnasium is planning to build for the near future.

• 대한후두음성언어의학회지
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• 제9권2호
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• pp.134-141
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• 1998

Mutational falsetto is a kind of voice disorders due to the failure to acquire proper low-pitched voice during the puberty. The patients with mutational falsetto can produce the normal low-pitched voice by the surgical treatment, like the type III-thyroplasty, or the voice therapy. The present study is, focusing on the latter treatment, to consider the efficiency of voice therapy for the mutational falsetto. The 7 patients who were diagnosed as mutational falsetto by the laryngologists, and treated by the voice therapist were selected as subjects. Their voices of pretherapy and posttherapy were analyzed on the aspects of acoustics and aerodynamics. Acoustic analysis was done by the MDVP(Multidimensional Voice Program) of CSL(Computerized Speech Lab, Kay Elemetrics, Co.), and aerodynamic analysis, by the Maximum Sustained Phonation of Aerophone II(Kay Elemetrics, Co.). By these measurements, we could find that fundamental frequency(F0) was significantly lowered, on the average, 65Hz. Maximum phonation time(MPT) was increased 4.57 second, and shimmer was decreased 1.644%, respectively, and each changes was statistically significant, too. On the average, jitter was decreased 0.499%, mean flow rate(MFR) was decreased 27.71ml/sec, and NHR was increased 0.023 which was the only parameter not showing improvement. But the changes of jitter, MFR and NHR were not statistically significant.

• The Journal of the Acoustical Society of Korea
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• 제16권3E호
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• pp.50-55
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• 1997

Based on the anthropometric data of Korea male adults, a head and torso simulator(HATS) is constructed to measure its head related transfer functions (HRTFs) which can be used for three dimensional (3-D) sound localization. The HRTFs binaural impulse responses, are measured in an anechoic chamber using a burst maximum length sequence (MLS) signal of 65,535 samples and 32,768 samples acquisition at the sampling rate of 75.47kHz. Also measured are the impulse responses of a driving loudspeaker and some headphones for sound reproduction to get the exact HRTF of the HATS-alone. Through a post-processing procedure, the impulse-version HRTFs at the sampling frequency of 44.1 kHz, which have filter lengths of 512 points, are finally obtained. As an application of the measured HRTFs, a 3-D sound processor for headphone reproduction has been developed. The signal intervals to be processed can be selected and each interval is manipulated to have its diretionality and distance information by using corresponding HRTF and energy control.

• The Journal of the Acoustical Society of Korea
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• 제28권2E호
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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.

• 한국소음진동공학회논문집
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• 제12권6호
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• pp.431-436
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• 2002

The interior sound pressure level of the Korean high-speed train(KHST) is predicted by geometrical acoustic method. For the Purpose of assuring the prediction of Interior noise of KHST by the geometrical acoustic scheme, calculated sound level values of the Korean train express(KTX) by Identical geometrical method are compared with measured values of KTX prototype vehicle by experiment. Contribution of individual sound source of KHST vehicle Into the interior response positions is calculated and sound sources are classified in influential order. Hence, it is reasonable approach to reduce sound power of most contributing noise source first. Sensitivity of the interior response position's sound pressure level (SPL) with respect to train wall sections' transmission loss are carried on and acoustically sensitive spot is identified, for example window area for passenger cabin case. Those contribution and sensitivity analysis results are suggested to design quieter train efficiently.

• 소음진동
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• 제9권1호
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• pp.184-188
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• 1999

Noise regulation of heavy construction machinery is getting stricter： 3 dB per every 4 year in European community. To meet this requirement many engineers have adopted the enclosing structures with thick absorbing materials and small opening, This increases internal temperature of the enclosure which have engine systems such as electric equipment that are vulnerable to heat, and engine block and muffler that can be regarded as heat sources. So noise control engineers have to consider a coupling problem: combining heat balance and noise reduction. This paper describes this approach by introducing simple heat transfer theory and SEA. The enclosing system of the loader whose enclosing structure consists of two rooms is investigated to show the validity of this method. The results represent that the simple heat transfer theory can be useful to estimate cooling performance when it is linked together by the back pressure theory in duct system. and the radiated noise can also be estimated by the SEA. Therefore a designer can use these approaches to define the opening ratio of an enclosure and the mass flow rate of air considering radiating noise.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1158-1166
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• 2009

Future luxury car must satisfy the improvement of the luxury sound quality on the vehicle interior noise. Previously, we have analyzed vehicle interior noise by dB(A) based analysis. However, dB(A) has very little to do with the psychological satisfaction of the consumers. People want a sound that is characteristic and refined not a sound that is quiet and common. Subjective test were conducted to determine the relationship between subject' s responses and calculated metric values. People choose the most luxury sound among the various vehicle interior noise. And the purpose of this study is that we understand the metrics which constitute the luxury vehicle sound. We have analyzed vehicle interior noise by using the statistical analysis such as multiple regression method and correlation method. And we organized the index of the luxury sound quality.

• 음성과학
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• 제15권2호
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• pp.145-156
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• 2008

The purpose of this study was to investigate the reason why puberphonia patients revisit hospitals after completion of its treatment and the effect of visual voice therapy on voice improvement. The subject the study included are two puberphonia patients who had been diagnosed by laryngologists. The patients who were diagnosed as puberphonia by the laryngologist and treated by the a speech pathologist, completed their treatment and revisited hospital. The study used laryngoscopy, acoustic and aerodynamic analysis before and after voice treatment to investigate what change happens and why generalization of treatment effect did not occur naturally in the daily life. Their voices of pre-therapy and post-therapy were analyzed on the aspects of acoustics, aerodynamics and laryngeal endoscopy. As a result, it was found that fundamental frequency(Fo) was significantly lowered in respect of acoustic change and maximum phonation time(MPT) was increased to some extent in respect of aerodynamic change. In addition, there was a laryngoscopic change and commissure glottic chink disappeared generally in the phonation. The reason why the generalization did not occur naturally in one’s daily routine was mainly due to the fact that high-pitched voicing was used for a long time. Other than that reason, negative reaction or attitude of surrounding people and lack of confidence were to blame for failure of generalization.

• 대한토목학회논문집
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• 제36권2호
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• pp.191-196
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• 2016

파동의 에돌이와 공명식 머플러 원리를 이용하여 통풍형 방음을 구현하고 그 이론을 설명하였다. 이 방음기술은 차단하고자 하는 주파수영역의 선택이 가능하다. 방음벽을 이중으로 만들고 그 사이를 비워, 방음벽의 구멍을 통해 들어온 음파가 내부에서 공진하여 소멸되도록 하였다. 두께 8cm인 공진통마다 직경 5cm의 공기구멍을 2개씩 뚫고 실험한 결과 넓은 주파수영역대서 평균 25dB정도의 차음효과가 있었다. 일본 컴넥스사의 산란에 의한 투과손실만 있는 경우와의 차음효과를 비교한 결과 같은 통풍능력인 경우에 적어도 10dB이상 차음효과가 높았다. 또한 컴넥스사의 기술은 차음주파수 영역을 선택할 수 없다는 한계가 있었다.