• Title/Summary/Keyword: acoustics

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Low-noise Design of Passage of Idle Speed Control Actuator In Automotive Engines Using Scaling Laws for Noise Prediction (소음예측 비례식을 이용한 자동차 엔진 공회전 속도 제어 장치 유로의 저소음 설계)

  • Cheong, Cheol-Ung;Kim, Jae-Hyun;Kim, Sung-Tae;Park, Yong-Hwan;Lee, Soo-Gab
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.8
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    • pp.683-692
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    • 2007
  • Recently, plastic products in air-intake parts of automotive engines have become very popular due to advantages that include reduced weight, constricted cost, and lower intake air temperature. However, flow-induced noise in air-intake parts becomes a more serious problem for plastic intake-manifolds than for conventional aluminum-made manifolds. This is due to the fact that plastic manifolds transmit more noise owing to their lower material density. Internal aerodynamic noise from an idle speed control actuator(ISA) is qualitatively analyzed by using a scaling law, which is expressed with some flow parameters such as pressure drop, maximum flow velocity, and turbulence kinetic energy. First, basic flow characteristics through ISA passage are identified with the flow predictions obtained by applying computational fluid dynamics techniques. Then, the effects on ISA passage noise of each design factors including the duct turning shape and vane geometries are assessed. Based on these results, the preliminary low noise design for the ISA passage are proposed. The current method for the prediction of internal aerodynamic noise consists of the steady CFD and the scaling laws for the noise prediction. This combination is most cost-effective, compared with other methods, and therefore is believed to be suited for the preliminary design tool in the industrial field.

Voice Analysis and Videostroboscopic Findings before and after Laryngomicrosurgery of Intracordal Cysts (성대낭종환자에서의 후두미세수술전후의 음성언어분석비교)

  • 고윤우;배정호;윤현철;정태영;김광문;최홍식
    • Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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    • v.11 no.1
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    • pp.12-19
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    • 2000
  • Background and Objectives : Dysphonia may be secondary to many different type of benign vocal cord lesions such as vocal polyp, vocal nodule, Reinke's edema, and intracordal cyst. Diagnosis and treatment of intracordal cysts are more difficult than other benign vocal cord lesions. But postoperative voice analysis of intracordal cyst have rarely been reported in the literature. The purpose of this study is to analyze aerodynamic and acoustic results and videostroboscopic findings before and after laryngomicrosurgery. Materials and Methods : We reviewed the pre and post-operative voice analysis results and videostroboscopic findings of 15 surgically treated patients of intracordal cysts at Severance hospital from Jun. 1997 to Nov. 1999 retrospectively. They were diagnosed with videostroboscopic findings, surgical findings, and pathologic reports. Their pre and post-operative speech were analyzed with MDVP(Multi Dimension Voice Analysis Program) of CSL(Computerized Speech Lab) and Aerophone II. Their pre and post-operative mucosal wave of true vocal cord was analyzed with videostroboscopy. In order to compare this results with normal group, 10 of normal persons were evaluated with same methods. Results : After the operation, mucosal wave of true vocal cord was improved in all patients. Postoperative acoustic and aerodynamic results were improved in almost parameters, but they did not reach the normal value. Conclusions : Videostroboscopy was essential in diagnosing intracordal cysts. By comparing the acoustic and aerodynamic results and video-stroboscopic findings before and after the laryngomicrosurgery, postoperative vocal function was defined more accurately and objectively. Almost parameters may be useful in assessing the quantitative changes in vocal quality before and after the laryngomicrosurgery.

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Development of acoustic emission monitoring system for the safety of geotechnical structures (지반구조물 안전감시용 미소파괴음 계측시스템 개발)

  • Cheon, D.S.;Jung, Y.B.;Park, E.S.
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.16 no.5
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    • pp.471-485
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    • 2014
  • The monitoring method of geotechnical structures using acoustic emission(AE) and microseismicity(MS) is to detect the microscopic deformation and fracture behavior in the inner structures by measuring induced acoustics and vibrations. It can identify a pre-indication of failure by taking advantage of the characteristics that the amount and occurrence rates of AE and MS increase rapidly prior to large scale destruction of the target structures. The monitoring system consisting of high-quality sensors, high-speed data acquisition device and the operation program is required for the practical application of this method. Recently, the AE and MS monitoring systems have been localized. In particular, the developed operation software which can analyze and interpret the measured signals was demonstrated through a number of applications to domestic fields. This report introduces the configuration and features of developed monitoring system, then the challenges and future direction of AE monitoring in geotechnical structures are discussed.

A Study on the Speech Transmission Index Method for Estimating Articulation of Loudspeaking Telephony (음성전송지수를 이용한 확성전화기의 명료도 평가 방법)

  • Jang, Dae-Young;Kang, Seong-Hoon;Sim, Dong-Yeon;Kim, Chun-Duck
    • The Journal of the Acoustical Society of Korea
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    • v.13 no.5
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    • pp.32-39
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    • 1994
  • The speech transmission quality in telephone is quantified in terms of loudness rating, but this method has been validated only for the handset telephony. The transmission quality of loudspeaking telephony in any room must be evaluated not only with speech transmission but also with background noise, echo and reverberation since the effect of room acoustics is much stroger for loudspeaking telephoy. Therefore, it requires a better approach to specify the quality of loudspeaking telephony. By calcuating the speech transmission index (STI), a physical method for measuring the quality of speech transmission was proposed by Steeneken. In this paper, the application of a STI method for estimating articulation of loudspeaking telephony was discussed. And the STI measurement system with high speed calculation was also three rooms, having different reverberation times. The result show that the STI decreases as the reverberation time of rooms increases. It suggests that speech transmission index method can be useful evaluating articulation of a loudspeaking telephony including the sound field characteristics.

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Investigation on lamb wave propagation in silicon wafer using large aperture line-focused transducer (대구경 선집속 탐촉자를 이용한 실리콘 웨이퍼에서의 램파 전파 특성 분석)

  • Chung, Yoonjae;Yang, Seung Soo;Yu, Minjae;Kim, Young H.
    • The Journal of the Acoustical Society of Korea
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    • v.37 no.4
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    • pp.174-180
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    • 2018
  • In this study, the propagation characteristics of Lamb waves in anisotropic silicon wafers of (100) and (111) direction were investigated by PVDF (Polyvinylidene Fluoride) line-focused transducer. The modified V(f,z) method was used because the Lamb waves are dispersive. For confirming the anisotropy, a line-focused transducer was used and the silicon wafer was rotated 180 degrees at intervals of 1 degree. As a result, $A_0$ and $S_0$ modes were observed. The speed of $S_0$ mode according to propagation direction showed anisotropy which is associated with the crystal structure, and the speed of $A_0$ mode was isotropic. The result is consistent with the crystal structure of silicon and the mechanism of vibration of each Lamb wave modes.

Studying Carbon Coating on the Surface of Nano-sized Fe Particle by Mössbauer Analysis (뫼스바우어 분광법에 의한 Fe-나노입자의 탄화물 코팅에 관한 연구)

  • Oh, Sei-Jin;Choi, Chul-Jin;Kim, Jin-Chun;Kwon, Soon-Ju;Jin, Sang-Ho
    • Journal of the Korean Magnetics Society
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    • v.15 no.3
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    • pp.172-176
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    • 2005
  • Four nano-sized Fe-nano particle samples synthesized by Chemical Vapor Condensation (CVC) were analyzed using $M\ddot{o}ssbauer$ spectroscopy, XRD, BET and TEM. The samples were consisted as functions of carrier gas and decomposition temperature. The synthesized nanoparticles consisted of two- or three-layers with the circular shape. The average particle size was increased with increasing the decomposition temperature. At $500^{\circ}C$ for the decomposition temperature, $Fe_3C$ was formed more under the environment of CO carrier gas than that of $CH_4$. However, at $1,100^{\circ}C$, almost of Fe-nano particles were transformed into $Fe_3C$ with using both carrier gas.

The Changes in the Closed Qutient of Trained Singers and Untrained Controls Under Varying Intensity at a Constant Vocal Pitch (음도 고정 시 강도 변화에 따른 일반인과 성악인 발성의 성대접촉률 변화 특성의 비교)

  • Kim, Han-Su;Jeon, Yong-Sun;Chung, Sung-Min;Cho, Kun-Kyung;Park, Eun-Hee
    • Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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    • v.16 no.1
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    • pp.28-32
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    • 2005
  • Background and Objectives : The most important two factors of the voice production are the respiratory function which is the power source of voice and the glottic closure that transform the air flow into sound signals. The purpose of this study was to investigate the differences between trained singers and untrained controls under varying intensity at a constant vocal pitch by simulataneous using the airway interruption method and electroglottography(EGG). Materials and Methods : Under two different intensity condition at a constant vocal pitch(/G/), 20(Male 10, Female 10) trained singers were studied. Mean flow rate(MFR), subglottic pressure(Psub) and intensity were measured with aerodynamic test using the Phonatory function analyzer. Closed quotients(CQ), jitter and shimmer were also investigated by electroglottography using Lx speech studio. These data were compared with that of normal controls. Results : MFR and Psub were increased on high intensity condition in all subject groups but there was no statistically significance. Statistically significant increasing of CQ. were observed in male trained singers on high intensity condition (untrained male : 51.31${\pm}$3.70%, trained male :55.52${\pm}$6.07%, p=.039). Shimmer percent, one of the phonatory stability parameters, was also decreased statistically in all subject groups(p<.001). Conclusion : The trained singers' phonation was more efficient than untrained singers. The result means that the trained singers can increase the loudness with little changing of mean flow rate, subglottic pressure but more increasing of glottic closed quotients.

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A Study on the Evaluation of Material Degradation for 1Cr-1Mo-0.25V Steel using Linear and Nonlinear Ultrasonics (선형 및 비선형 초음파를 이용한 1Cr-1Mo-0.25V의 열화평가에 관한 연구)

  • Kim, Jeong-Pyo;Seok, Chang-Sung;Song, Sung-Jin;Kim, Young-Hwan
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.5
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    • pp.549-555
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    • 2001
  • Ultrasonic is a powerful nondestructive technique for getting the information of flaws and material properties of in-services facilities. We prepared 4 different 1Cr-1Mo-0.25V specimens by Isothermal aging at $630^{\circ}C$. We evaluated material degradation using ultrasonic parameters, velocity, attenuation and harmonic generation. Attenuation and nonlinear parameter derived from harmonic generation efficiency increased as degradation. Especially the second harmonic of the fundamental wave in the 1,820h aging material was observed to exceed 20dB more than that in the un-aged material. But velocity remained virtually the same for all specimens. We concluded that nonlinear parameter and attenuation are sensitive to material degradation, but velocity was not. It'll be a good parameter for evaluating the material degradation.

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Assessment of statistical sampling methods and approximation models applied to aeroacoustic and vibroacoustic problems

  • Biedermann, Till M.;Reich, Marius;Kameier, Frank;Adam, Mario;Paschereit, C.O.
    • Advances in aircraft and spacecraft science
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    • v.6 no.6
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    • pp.529-550
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    • 2019
  • The effect of multiple process parameters on a set of continuous response variables is, especially in experimental designs, difficult and intricate to determine. Due to the complexity in aeroacoustic and vibroacoustic studies, the often-performed simple one-factor-at-a-time method turns out to be the least effective approach. In contrast, the statistical Design of Experiments is a technique used with the objective to maximize the obtained information while keeping the experimental effort at a minimum. The presented work aims at giving insights on Design of Experiments applied to aeroacoustic and vibroacoustic problems while comparing different experimental designs and approximation models. For this purpose, an experimental rig of a ducted low-pressure fan is developed that allows gathering data of both, aerodynamic and aeroacoustic nature while analysing three independent process parameters. The experimental designs used to sample the design space are a Central Composite design and a Box-Behnken design, both used to model a response surface regression, and Latin Hypercube sampling to model an Artificial Neural network. The results indicate that Latin Hypercube sampling extracts information that is more diverse and, in combination with an Artificial Neural network, outperforms the quadratic response surface regressions. It is shown that the Latin Hypercube sampling, initially developed for computer-aided experiments, can also be used as an experimental design. To further increase the benefit of the presented approach, spectral information of every experimental test point is extracted and Artificial Neural networks are chosen for modelling the spectral information since they show to be the most universal approximators.

A Study on the Emotional design approach in the Therme Vals designed by Peter Zumthor (피터 쥼터의 썸 발즈에 나타난 감성 디자인 접근에 관한 연구)

  • Woo, Ji-Yeon
    • Korean Institute of Interior Design Journal
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    • v.19 no.3
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    • pp.77-85
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    • 2010
  • The Therme Vals is a hotel and spa which combines a complete sensory experience designed by Peter Zumthor. This study aims to find emotional design approaches of the Therme Vals through references, observation from site visit, interview and discussion related to this topic. This space was designed for visitors to luxuriate and rediscover the ancient benefits of bathing. The combinations of light and shade, open and enclosed spaces and linear elements make for a highly sensuous and restorative experience. The study observed the emotional design characteristics of the Therme Vals through space approach, aesthetic and experiential sides. For space approach side, emotional experience in gradual process to approach the space was mentioned, for aesthetic side, mystical combination of light, stone and water was observed, for experiential side, 5 senses experience and space programing for adjusting the density of the space were observed. This study found that the spa has the quality of spiritual, soul-touching delight like religious experience. The fascination for the mystic qualities of a world of stone within the mountain, for darkness and light, for light reflections on the water or in the steam saturated air, pleasure in the unique acoustics of the bubbling water in a world of stone, the ritual of bathing-all these notions were explained in Peter Zumthor's construction details. In the result of the interview and discussion, people love the space and praised it highly for the emotional design regardless of space experience, age, sex or ethnicity. Emotional design approaches based on human nature, materiality, and memory of the places is more powerful than other emotional design ideas with technical devices, special themes, digital effects, vivid colors and shapes.