음향모드 분할 현상을 피하는 음향공명기 동조방법에 대한 수치적 연구

박이선,손채훈 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.2

음향불안정을 억제하는 수동제어기구 중 하나인 음향공명기의 mode split을 일어나지 않게 동조시키기 위해서는 고유주파수의 음향에너지 특성에 따른 정확한 동조가 필요하다. 여기서는 고유주파수를 응용해서 정확한 동조를 시킬 수 있는 방법을 소개하겠다. 음향공명기 모델로서 Helmholtz 형태의 공명기가 채택되었고, 진동해석을 통해 고유주파수를 구하였다. 유해 모드로 알려져 있는 제1종방향 음향모드와 제1접선방향 음향모드를 새로운 해석 방법에 의한 감죄를 통해 검증을 하였으며, peak의 좌우의 음향에너지가 균형을 이루게 함에 따라 mode split 된 peak이 1개의 peak으로 변화하는 과정을 나타내었다. 이를 토대로 mode split 없는 감쇠를 위해서는, 억제하고자 하는 음향모드의 peak을 중심으로 한 좌우의 음향에너지가 균형을 이룰 때 모드분할 현상이 나타나지 않으면서 그 음향모드를 감쇠시킬 수 있게 동조시킬 수 있음을 알 수 있었다. Acoustic behavior in gas turbine combustion chamber with acoustic cavity is numerically investigated by adopting linear acoustic analysis. Helmholtz-type resonator is employed as a cavity model to suppress acoustic instability passively. The tuning frequency of acoustic cavity is adjusted by varying the length of acoustic cavity. Through harmonic analysis, acoustic pressure responses of chamber to acoustic oscillating excitation are shown and the resonant acoustic modes are identified. Acoustic damping effect of acoustic cavity is quantified by damping factor. As the tuning frequency approaches the target frequency of the resonant mode to be suppressed, mode split from the original resonant mode to lower and upper modes appears and thereby damping effect is degraded significantly. A method to tune acoustic resonator preveting acoustic-mode split is suggested considery energy balance between left and of the peak response right sides.

구조-음향 연성 시스템의 진동모드에 의한 소음 예측

황재승(Jae-Seung Hwang),송민정(Min-Jeong Song),류종관(Jong-Kwan Ryu) 한국소음진동공학회 2021 한국소음진동공학회 논문집 Vol.31 No.6

An acoustic domain combined with a flexible structure induces a unique sound field due to the interaction between a fluid and the structure at acoustic-structure boundaries. In this study, the characteristics of the acoustic modes induced by a structural vibration mode were examined, and the acoustic noise from the vibration mode was predicted using a numerical analysis. For this, a reverberation chamber with a shell at one side was constructed as a finite-element model, and the modal parameters of the vibration and acoustic modes were evaluated using an eigenvalue analysis. In addition, the structural vibration and sound pressure caused by a impulse load impacting the shell were analyzed with a time-domain acoustic-structure coupling analysis, and an acoustic mode was analyzed from a specific vibration mode by identifying the vibration and acoustic modal response from the measured responses. The framework for predicting the acoustic mode presented in this study can enhance the understanding of sound pressure induced by vibration. Further, it is expected that this framework could be applied to predict the heavy weight floor impact sound from the vibration of a slab in an apartment.

보일러 튜브군의 음향공진 회피를 위한 음향배플의 위치에 따른 FEM 음향모드해석

안성종(Sung Jong Ahn),주영호(Young Ho Ju),김철홍(Cheol Hong Kim) 한국소음진동공학회 2012 한국소음진동공학회 학술대회논문집 Vol.2012 No.4

A flow induced mechanical vibration and acoustic resonance should be considered at design stage because they are mainly occurred in the tube bank of boiler. Acoustic resonance is occurred when the vortex shedding frequency of tube bank coincides with the acoustic natural frequency of the cavity. Effective solution to avoid acoustic resonance is installing acoustic baffles in the tube banks parallelly inside of the flow cavity. Thus, location and number of acoustic baffles should be exactly calculated to eliminate the acoustic resonance. This paper presents case study of acoustic resonance due to inappropriate number and location of acoustic baffles. Measured frequency and mode in the study is verified by FEM acoustic modal analysis. The number and location of acoustic baffles to avoid acoustic resonance are calculated by using FEM acoustic modal analysis.

3차원 파워흐름유한요소법을 이용한 인접한 두 실내에서의 진동음향 해석

김성희(Kim, Sung-Hee),홍석윤(Hong, Suk-Yoon),길현권(Kil, Hyun-Gwon),송지훈(Song, Jee-Hun) 한국소음진동공학회 2010 한국소음진동공학회 논문집 Vol.20 No.1

Power flow analysis(PFA) methods have shown many advantages in noise predictions and vibration analysis in medium-to-high frequency ranges. Applying the finite element technique to PFA has produced power flow finite element method(PFFEM) that can be effectively used for analysis of vibration of complicated structures. PFADS(power flow analysis design system) based on PFFEM as the vibration analysis program has been developed for vibration predictions and analysis of coupled structural systems. In this paper, to improve the function of vibro-acoustic coupled analysis in PFADS, the PFFEM has been extended for analysis of the interior noise problems in the vibro-acoustic fully coupled systems. The vibro-acoustic fully coupled PFFEM formulation based on energy coupled relations is extended to structural system model by using appropriate modifications to structural-structural, structural-acoustic and acoustic-acoustic joint matrices. It has been applied to prediction of the interior noise in two room model coupled with panels, and the PFFEM results are compared to those of statistical energy analysis(SEA).

성대 양성점막 질환에서 수술 전후 음질변화를 객관적으로 반영하는 음향지표 분석

서인효,정동식,한현주,문정환,정필상,이상준 대한이비인후과학회 2016 대한이비인후과학회지 두경부외과학 Vol.59 No.11

Background and Objectives The aim of this study was to compare between preoperative and postoperative voices by subjective auditory perceptual evaluation and objective acoustic analysis. The study also analyzed the acoustic parameters that best reflected the auditory perceptual characteristics in laryngeal microsurgery. Subjects and Method The records of 49 patients who had been diagnosed as benign vocal fold mucosal diseases and had undergone laryngeal microsurgery were retrospectively analyzed. Preoperative and postoperative voices were assessed by auditory perceptual evaluation using the GRBAS Scale and acoustic analysis using Multi-Dimensional Voice Program (MDVP) and Analysis of Dysphonia in Speech and Voice (ADSV). Correlation between auditory perceptual characteristics and acoustic parameters was analyzed. Results Auditory perceptual evaluation showed that the patients’ voices were improved after the operation. Several acoustic parameters of MDVP related to short-term and long-term variability showed significant improvement. Also, there were significant differences in several cepstral/spectral parameters of ADSV after operation. In the correlation analysis, the overall grade (G) of the GRBAS Scale showed highest correlation with the cepstral spectral index of dysphonia (CSID) (r=-0.700). The roughness (R) of GRBAS Scale was correlated with the smoothed amplitude perturbation quotient of long-term variability of MDVP (r=0.468), breathiness (B) with cepstral peak prominence (r=-0.703) and strain (S) with CSID (r=0.650) (p<0.01). Conclusion Our results showed that the acoustic parameters were related to the long-term variability of MDVP, and the parameters of cepstrum/spectrum were useful for the objective assessment of voice quality in patients who received laryngeal microsurgery. These parameters were also useful for the quantification of voice quality and abnormality of phonation. Korean J Otorhinolaryngol-Head Neck Surg 2016;59(11):775-9

위성 발사체 페어링 내부음향 해석

서상현(Sang-Hyeon Seo),박순홍(Soon-Hong Park),정호경(Ho-Kyeong Jeong),장영순(Young-Soon Jang) 한국소음진동공학회 2011 한국소음진동공학회 학술대회논문집 Vol.2011 No.10

Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

위성 발사체 페어링 내부음향 해석

서상현(Seo, Sang-Hyeon),박순홍(Park, Soon-Hong),정호경(Jeong, Ho-Kyeong),장영순(Jang, Young-Soon) 한국소음진동공학회 2011 한국소음진동공학회 논문집 Vol.21 No.12

Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

구개성형술 전후 구개열 말소리의 음향학적 분석: 증례 보고

양지형 대한구순구개열학회 2022 대한구순구개열학회지 Vol.25 No.2

The purpose of the primary cleft palate surgery is to recover the anatomical structure, securefunctions such as speaking and swallowing, and induce the growth of the right maxillaryface. VPI(Velopharyngeal Inadequacy) may occur after the primary cleft palate surgery,and the purpose of the secondary surgery performed at this time is to improve VPI andthereby increase clarity and communication efficiency. Videofluoroscopic examinationand endoscopic nasopharynx examination can be performed to confirm the improvementof VPI after secondary surgery, and acoustic evaluation using a test device and perceptualexamination by speech and language pathologists(SLP) can be performed to evaluate speechsounds. Acoustic analysis using assessment instruments is useful because it can proveclinical diagnosis by experts, identify fine voice problems and their causes, and quantify theseverity of speech problems. Nevertheless, there are not many researches that can presentacoustic analysis for cleft palate speech and provide meaningful statistical data. Through thecase of an adult who improved velopharyngeal functions after secondary cleft palate surgery,this report can introduce specific examples of acoustic analysis of cleft palate speech andprovide the chances to review the usefulness and availability of acoustic analysis. '-

압전 단결정을 이용한 고감도 광대역 링 트랜스듀서의수중 음향특성 분석

민승기,임종범,안병선,윤홍우,권병진,이정현 한국소음진동공학회 2022 한국소음진동공학회 논문집 Vol.32 No.4

In this study, the design and underwater acoustic characteristics of a ring transducer composed of a piezoelectric single crystal as the active material was reported. The PIN-PMN-PT piezoelectric single crystals with improved thermal durability have superior piezoelectric performance compared to PZT-4, widely used in underwater acoustic sensors. A 33-mode ring transducer was designed and its acoustic characteristics were estimated through electro-mechanical-acoustic coupled analysis. Furthermore, the acoustic characteristics of the ring transducers, composed of piezoelectric single crystals or PZT-4, were compared. The piezoelectric single crystals ring transducer is expected to have a higher transmitting voltage response (TVR) and receiving voltage sensitivity (RVS) compared to the PZT-4 ring transducer due to a high electro-mechanical coupling coefficient. It is also expected to have wideband performance due to a low mechanical quality factor. The acoustic characteristics of the fabricated piezoelectric single crystals ring transducer were measured and analyzed with the results of the electro-mechanical-acoustic coupled analysis. Upon applying piezoelectric single crystals as active materials, the ring transducer provided high sensitivity and broadband performance.

M형 CIP법을 이용한 3차원 음장해석에 관한 연구

이채봉,오성관,Lee, Chai-Bong,Oh, Sung-Qwan 한국융합신호처리학회 2009 융합신호처리학회 논문지 (JISPS) Vol.10 No.4

본 연구에서는 유체역학 분야의 Yabe 박사 팀에 의해 제안된 CIP법을 이용한 3차원 시간영역 음장해석법의 정밀도에 대해서 자세한 검토를 하였다. 즉, 3차원 CIP 음장해석의 위상오차의 특성과 전파방향에 따른 오차를 명확히 하고, 본 수치 해석법의 유효성을 나타내었다. 다차원 CIP법으로는 M형, C형, A형이 있지만, 본 논문에서는 M형 CIP법을 이용한 음장해석의 정밀도에 대해 검토하였다. 또, 종래의 수치해석법으로 staggered-grid 모델을 이용한 FDTD법에 따른 계산결과와의 비교 검토를 하였다. 본 논문의 검토에 의해 같은 이산화조건에서는 CIP법이 FDTD법보다 해석법이 가진 분산성이 적고, CIP법으로 계산된 음압 파형이 FDTD법으로 계산된 음압 파형보다 변형이 적은 것을 알 수 있었다. The authors have investigated the acoustic field analysis using the Constrained Interpolation Profile(CIP) Method recently proposed by Yabe. The present study has examined the calculation accuracy of the three-dimensional (3-D) acoustic field analysis using the type-M CIP method. In this paper we show phase error of type-M CIP method and the dependence on the wave-propagation direction in the type-M CIP acoustic field analysis, and then demonstrate that it is effective for acoustic field analysis, compared with the FDTD and the exact solution. We show the dependency on the propagation angle in the CIP acoustic field analysis.