Measurement of Sound Transmission Loss by Using Impedance Tubes

정성수,김용태,이용봉,조승일,이종규 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2

The sound transmision los of several sound absorbent materials was measured by using an impedance tube and was compared with theoreticaly calculated values. The impedance tube system designed for the testing consisted of an upstream tube, a sample-holder section and a downstream tube. The transfer function method and a four-pole matrix analysis were used in measuring and calculating the sound transmision los, respectively. Good agrement betwen the measured and the theoretical values was obtained.

Characterization of the Acoustic Properties of Random Porous Media: Reticulated Vitreous Carbon and Aluminum Foam

Heui-Seol Roh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2

The acoustic properties of thermoacoustic stacks made from random porous media are exper- imentaly investigated using a hybrid two-microphone impedance method and a lumped-element technique. A two-microphone impedance tube is used to measure the specific acoustic impedance (SAI) of random porous reticulated vitreous carbon (RVC) and aluminum foam. The lumped- element technique is then used to determine the experimentaly derived thermoviscous functions, which produce the propagation constant and the characteristic impedance. The measured acoustic properties of the stacks are compared to calculated results obtained by asuming paralel, capil- lary tubes. These comparisons verify that the hybrid impedance measurement can provide useful acoustic properties and that the paralel capilary-tube-based thermoacoustic theory is valuable in predicting the acoustic properties of random porous media.

Electrical Impedance Tomography Technique for the Visualization of the Phase Distribution in an Annular Tube

Kim, Min Chan,Kim, Kyung Youn,Kim, Sin,Lee, Heon Ju,Lee, Yoon Joon 한국공업화학회 2002 Journal of Industrial and Engineering Chemistry Vol.8 No.2

The experimental and algorithmic works are conducted to obtain the phase distribution in the two-phase flow using the electrical impedance tomography (EIT) in an annular geometry. The finite element method (FEM) is employed in the forward problem and a regularized Newton-Raphson iterative method is used in the inverse problem. The reconstructed images based on our numerical algorithm and experimental works identify the position of dispersed phase. The quality of reconstructed image seems to be dependent on the number and position of the targets. It seems that our works can be used to visualize the phase distribution in an annular tube.

에코골재를 사용한 흡음재의 특성

김강덕,류유광,김유택,Kim, Kang-Duk,Ryu, Yu-Gwang,Kim, Yoo-Taek 한국결정성장학회 2008 한국결정성장학회지 Vol.18 No.6

산업현장에서 발생되는 다양한 종류의 폐기물을 이용하여 에코골재를 제조하였다. 에코골재는 폐기물을 분쇄하고 조립성형 후, 로타리 킬른에서 $1125^{\circ}C$/15 min의 조건으로 소성하여 제조되었다. 본 연구진에 의해 제조된 에코골재 K73(Coal bottom ash 70 wt%: Dredged soil 30 wt%)과 K631(Clay 60 wt%: Stone sludge 30 wt%: Spent bleaching clay 10 wt%)을 이용하여 경량 콘크리트 흡음재를 제조하였으며, 비교를 위해 독일에서 수입된 DL(독일산 'L'사 인공경량골재)을 이용한 흡음재 역시 같은 조건으로 제조하였다. 골재의 종류, 물-시멘트비(W/C=20, 25, 30%) 그리고 설계 공극률(20, 25, 30%)의 변화에 따른 흡음특성변화를 관찰하였다. 실험결과, 경량 콘크리트 흡음재의 실제 공극률은 설계 공극률보다 $5{\sim}10%$ 정도 높게 나타났다. 임피던스관을 이용한 흡음재의 흡음계수 측정 결과, K631골재를 이용한 경량 콘크리트 흡음재(W/C=20%, V=25%)가 1000, 3150 Hz에서 각각 0.88의 흡음계수를 나타내었다. Ecological lightweight aggregates were made by using the wastes come from various industrial fields. Wastes were crushed and pulverized by mills and a certain portions of wastes were mixed and formed by pelletizer like small beads. The formed lightweight aggregates were finally sintered with $1125^{\circ}C$/15 min conditions by using rotary kiln. Lightweight concrete sound absorbers were made of ecological lightweight aggregates K73 (Coal bottom ash 70 wt%: Dredged soil 30 wt%) and K631 (Clay 60 wt%: Stone sludge 30 wt%: Spent bleaching clay 10 wt%). For the reference, lightweight concrete sound absorbers made of DL (German made 'L' company LWA) were also made under the same conditions. Sound absorption characteristics were observed and measured according to the kinds of aggregates, water/cement ratio (W/C=20, 25, and 30%), and designed pore rates (V=20, 25, and 30%). The pore rates of the lightweight concrete sound absorber were turned out to be 5 to 10% higher than designed ones. Absorption coefficient of the lightweight concrete sound absorber by using K631 aggregates with W/C=20% and V=25% conditions was 0.88 at 1000 and 3150 Hz from the measurement by the impedance tube.

Acoustic characteristic of bio-composite micro-perforated panel (BC-MPP) backed with natural fiber

Faridah Wahab,Tan Wei Hong,Mohamad Haziman Mohamad Azhar,Nor Hafizul Hilni Abdul Rahman 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.11

We investigated the sound absorption properties of a bio-composite microperforated panel (BC-MPP) with a combination of backed-structure and several types of natural fibers such as loofah, kapok, and coconut coir. The sound absorption coefficient (SAC) of different combinations of natural fibers samples was obtained by using a two-microphone impedance tube. In addition, three models, including Delany-Bazley model, Maa theory, and electroacoustical analogy, were employed to estimate the SAC value of natural fiber, BC-MPP, and BC-MPP with a backed structure, respectively. The experimental results demonstrate that the SAC value was increased to almost 0.99 as compared to BC-MPP alone when natural fiber was introduced at the back of BC-MPP either by insertion in the hole of backed structure or attached directly at the back of BC-MPP. The SAC peak also shifted to a lower frequency bandwidth with the highest peak obtained at 930 Hz, 800 Hz and 640 Hz for MPP with coconut husk, BC-MPP with kapok and BC-MPP with loofah, respectively. The absorption frequency was also observed slightly wider than BC-MPP without natural fiber. In comparison of BC-MPP with loofah and BC-MPP with others natural fibers, the insertion of kapok and coconut coir in the hole of backed structure provides a wider effective sound absorption coefficient. The comparison of experimental result with the theoretical calculation shows that the SAC obtained from experiment provides higher SAC value over the theoretical model for both BC-MPP and BCMPP backed structure.

Development of a Practical Two-Microphone Impedance Tube Method for Sound Transmission Loss Measurement of Sound Isolation Materials

Ro, Sing-Nam,Hwang, Yoon,Lee, Dong-Hoon The Society of Air-Conditioning and Refrigerating 2003 International Journal Of Air-Conditioning and Refr Vol.11 No.3

This study developed a practical two-microphone impedance tube method to measure the sound transmission loss of sound isolation materials without the use of an expensive reverberation room or an acoustic intensity probe. In order to evaluate the validation and applicability of the two-microphone impedance tube method, sound transmission losses for several sound isolation materials with different surface density and bending stiffness were measured, and the measured values were compared with the results from the reverberation room method and the theory. From the experimental results, it was found that the accuracy of sound transmission loss obtained by the impedance tube method depends upon the diameter size of the impedance tube (i.e., tested sample size). For sound isolation materials having relatively large bending stiffness such as acryl, wood, and aluminum plates, it was found that the impedance tube method proposed by this study was not valid to measure the sound transmission loss. On the other hand, for sound isolation materials having relatively small bending stiffness such as rubber, polyvinyl, and asphalt sheets, the comparisons of transmission loss between the results from the impedance tube method and the theory showed a good agreement within the range of the frequencies satisfying the normal incidence mass law. Therefore, the two-microphone impedance tube method proposed by this study can be an effective measurement method to evaluate the sound transmission loss for soft sound isolation sheets having relatively small bending stiffness.

두 개의 마이크로폰이 부착된 임피던스관법을 이용한 차음시트의 음향투과손실 측정

이동훈,용호택,이승 대한설비공학회 2002 설비공학 논문집 Vol.14 No.1

The main objective of this study is to propose a practical two-microphone impedance tube method to measure the sound transmission loss for flexible sound isolation sheets without the use of the time-consuming and expensive reverberation room. This method was based on the sound decomposition theory developed by Seybert using the spectral density functions of the incident and reflected sound waves. In order to verify the validity of the experimental results, the measured sound transmission losses from the proposed method were compared with the measured data from the reverberation room method and the calculated data from the theory satisfying the mass law of sound isolation material. The resulted trends of the sound transmission losses versus frequencies for several different sound isolation sheets were almost same for each other and agreed quite well in both methods except at some low frequency region. From the experimental results, it was found that the accuracy of sound isolation capability obtained by two-microphone impedance tube method depends upon the microphone spacing, the distance from the first microphone to the test sample surface and the test sample location.

편측 중이염환자의 건측 Impedance 특성

이동훈,김민성,조봉구,오세준,공수근 대한이비인후과학회 부산,울산,경남 지부회 2023 임상이비인후과 Vol.34 No.4

Background and Objectives: The normal ear of patients with unilateral otitis media is also often abnormal. Therefore, using the Williams test (Y-226 Hz), we compared the impedance of the normal ear of patients with unilateral otitis media with the impedance of subjects with bilateral normal ears to provide additional data for the evaluation of the normal ear of patients with unilateral otitis media. Materials and Methods: The Williams test (y-226 Hz) impedance characteristics of the normal E-tube (40 ears) and the normal E-tube (33 ears) of patients with unilateral otitis media were compared and analyzed using t-test. Results: The static compliance (SC) in the normal ear of patients with unilateral otitis media was significantly higher than the SC in both normal ears. And the ears of the unilateral otitis media group were located at relatively significantly negative pressure in all atmospheric pressure eustachian tube function test (ETFT ), positive pressure ETFT, and negative pressure ETFT. Additionally, pressure changes and symmetry were relatively good in the ears of the normal group. Conclusion: Even in the normal ear of a patient with unilateral otitis media, there is a possibility that there may be a minor problem with the tympanic cavity, so care must be taken during examination and diagnosis.

병원 중환자의 경관유동식 공급 현황 및 영양상태 변화

박은경,이종호,임현숙 대한영양사협회 2001 대한영양사협회 학술지 Vol.7 No.3

It is important to supply adequate nutrition to critically ill patients, whose gastrointestinal system is properly functioning, through the enteral tube feeding if oral intake is impossible. In this study we investigated the changes in nutritional status with enteral tube feeding according to the volume required. We investigated the volume ordered according to the patient's requirements, volume infused according to the volume ordered in 41 enteral tube feeding patients in intensive care unit from Jannuary to July, 2000. Body weight, serum albumin level, and total lymphocyte count were evaluated to assess nutritional status. The mean fasting period was 5 days before the enteral feeding and patients whose fasting period over 3 days were 51%. The mean enteral tube feeding period was 29 days and method of feeding was nasogastric, bolus feeding 6 times per day. The volume ordered was 69.7% of the patients' recommended calorie and volume infused was 86.6% of their volume prescribed. Accordingly, the volume infused was estimated 61.7% of their volume required. Only 44.6% of their reqiured volume was infused within 3 days after enteral tube feeding was started. It took 16 days in average to meet the patients' recommended calorie; 56% of subjects still did not fully met their requirements by the end point. Among the impeding factors in supplying enteral tube feeding, factors related to the number of feeding were high residual volume in stomach, vomiting, gastrointestinal bleeding, abdominal distension and surgery. Factors related to the actual infused volume were diarrhea, gastrointestinal bleeding, abdominal distension, airway management and tube reinsertion. Significant correlations were shown between the volume infused and changes in both the patients' weight and serum albumin level. Deviding the subjects into two groups by their infused volume, less than 70% and more than that, we compared the two to come up with a significant difference in their serum albumin level, -0.23 vs 0.21, and their body weight, -4.52 vs 0.12. In enteral tube feeding, the volume delivered in sufficient to the patients' energy requirement can affect their nutritional status in critically ill patient; adequate nutritional management plan is essential It is necessary to make every effort to educate clinical staff and to set up a unified management program to prescribe adequate ammount of energy for the patient's nutritional requirement.

Eustachian Tube Opening Measurement by Sonotubometry Using Perfect Sequences for Healthy Adults

Vilma Beleskiene,Eugenijus Lesinskas,Vaida Januskiene,Kristina Daunoraviciene,Darius Rauba,Justinas Ivaska 대한이비인후과학회 2016 Clinical and Experimental Otorhinolaryngology Vol.9 No.2

Objectives. The aim of this study was to establish the rate variation of sonotubometric measurements using a specific broadband class of signals, the so-called perfect sequences (PSEQ) among healthy adults and to identify an optimal and technically simple test to provoke Eustachian tube (ET) openings. Methods. Sonotubometry was performed on 105 healthy adult subjects. Three different consecutive maneuvers were performed for ET opening: dry swallowing, water swallowing (a small [2 mL] and a large [5 mL] water bolus). Values of the amplitude and duration of each measured ET opening were calculated. Results. A total of 6,300 measurements were performed. Sonotubometric ET openings were detected for all subjects but not for each measurement. In 6,180 of 6,300 measurements (98.1%), objective ET openings were registered. In 11 of 105 subjects (10.5%) at least one sonotubometric ET opening was not detected. The mean ET opening duration time and the mean sound amplitude similar for all performed test and were 270 (SD, ±96) msec, 13.48 (SD, ±6.57) dB. Conclusion. Sonotubometry based on PSEQ stimuli is a reliable methodology to assess the ET opening function in healthy subjects. Mean ET opening duration time and the mean sound wave amplitude performed similarly in all analysed tests, hence it might be concluded that dry (saliva) and water swallowing are reliable sonotubometric maneuvers and may be used when examining ET opening function. The size of a sip during water swallowing does not affect the sonotubometry result. All maneuvers can be equally used as the optimal test, and water swallow is most comfortable for the subject.