• The Journal of the Acoustical Society of Korea
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• v.41 no.5
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• pp.570-588
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• 2022

We scrutinized the acoustic outputs from the 70 shock wave generators of the 15 product models whose technical documents were available, among the 46 ballistic extracorporeal shock wave therapeutic devices of 11 domestic and 6 foreign manufacturers, approved by the Minster of Food & Drug Safety (Rep. Korea). We found that the acoustic Energy Flux Density (EFD), the most popular exposure parameter, was different by up to 563.64 times among shock wave generators at their minimum output settings and by up to 74.62 times at their maximum settings. In the same product model, the EFD was shown to vary depending on shock wave transmitters by up to 81.82 times at its minimum output setting and by up to 46.15 times at its maximum setting. The lowest EFD 0.013 mJ/mm² at the maximum output settings was much lower (2.1 %) than the maximum value 0.62 mJ/mm² at the minimum settings. The Large acoustic output differences (tens to hundreds of times)from the therapeutic devices approved for the same clinical indications imply that their therapeutic efficacy & safety may not be assured. The findings suggest the regulatory authority to revise her guideline to give clearer criteria for clinical approval and equality in performance, and recommend the authority to initiate a post-approval surveillance as well as a test in conformance between the data in technical documents and the real acoustic outputs clinically used.

• The Journal of the Acoustical Society of Korea
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• v.42 no.5
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• pp.469-490
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• 2023

Survey was carried out on the acoustic outputs from 12 shock wave fields produced by the 10 extracorporeal shock wave lithotriptors whose technical documents are available, among the 33 devices approved by the Ministry of Food & Drug Safety (MFDS).The results show that the acoustic outputs (P+, P-, efd, and E), critical to the therapeutic efficacy and the patient safety, are largely different between the devices. The maximum values of P+, P-, efd, and E vary up to 2.08, 3.72, 3.89, and 15.98 times, respectively. The acoustic output parameters are not thoroughly provided in the technical documents, and some of data (eg. efd) are suspected to be abnormal outside usual ranges. The large device to device differences in the shock wave outputs are likely to undermine equivalence between the ESWL devices approved for the same indication. To verify the reliability of the data in the technical documents of the approved devices and to confirm if the acoustic outputs from the devices in clinical use are the same as those in their technical documents, an authorized test laboratory should be available. A postapproval monitoring led by the regulatory agency is suggested to maintain the acoustic outputs from the ESWL devices that suffer from degrading in performance due to aging.

• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.303-317
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• 2020

Extracorporeal Shock Wave Therapy (ESWT) is an innovative treatment in chronic musculoskeletal pain management and cardiovascular diseases. In this study, we surveyed the acoustic shock wave outputs from the domestically used focal type ESWT devices. The survey data were collected through 30 technical documents registered to the Ministry of Food and Drug Safety (MFDS), Rep. Korea. The results show that the focusing geometry varies largely, 5 mm to 65 mm in the focal length, 3 mm to 30 mm in focal width, and 4 mm to 108 mm in focal depth. The maximum positive pressure (P+) ranges from 7 MPa to 280 MPa, the focal Energy Flux Density (EFD) from 0.0035 mJ/㎟ to 35 mJ/㎟, and the energy per pulse (E) from 0.737 mJ to 80.86 mJ. All domestic PE-type (five) and one EM-type domestic devices included in the analysis of the correlation between P+ and EFD are shown to be far beyond the usual ranges and do not comply with expected correlation so that the reliability of their data was suspected. For the suspected, post-performance tests are required by a recognized testing agency. MFDS guidelines need to be revised so that the pass criteria for the shock wave acoustic outputs can be based on the clinical tests for indications.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.329-332
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• 2000

목적으로 하는 특정 주파수에서 고출력의 음향에너지를 방사하는 단일음 전자형 수중스피커를 설계$\cdot$제작하고자 한다. 유한요소법과 이론식을 사용하여 진동판의 기계적 공진주파수를 구한 후 이를 토대로 전자형 수중스피커를 제작하였다. 간이수조 및 해상 실험을 통하여 280Hz-285Hz에서 최대 음압이 발생되고, SL을 산출한 결과 162dB로 충분히 높은 음향 출력을 가지므로서 어류 집어용 수중스피커로 적용 가능하다는 것을 확인하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.373-376
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• 2000

기존의 Push-Pull 트랜스듀서보다 간단한 구조를 가지며 출력을 한층 더 높이기 위해서 실린더 중앙에 구동부를 둔 새로운 구조의 Push-Pull 트랜스듀서를 설계하고자 한다. 유한 요소 상용 Package인 ANSYS를 이용하여 트랜스듀서의 모델을 구성한 후, 분석 시 고려되어 지는 길이, 반경, Endcap Edge 형상에 대해 변수로 설정, 변수들의 변화에 대한 음압의 변화 경향을 조사하여 최대 음압을 구현하기 위한 최적 길이, 반경, Endcap Edge 형상을 설정하였다. Endcap의 형상이 수직, 삼각형 형태의 트랜스듀서에서 나타난 결과에서 힘의 전달이 Edge형상이 수직일 때보다는 삼각형일 때가 더 좋은 것을 볼 수가 있었다. 또한 기존의 트랜스듀서를 유한 요소로 설계를 하여서 분석을 하였고, 기존의 트랜스듀서와 비교해 본 결과, 최적 설계한 트랜스듀서가 구조적으로 더 단순한 구조임에도 불구하고 더 큰 음압을 구현할 수 있는 고출력 트랜스듀서라는 것을 입증하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.311-314
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• 1999

본 연구에서는 저주파 대역에서 고출력 수중 음향센서로 사용되는 Class IV Flextensional 트랜스듀서의 여러 설계변수들에 따른 음압 변화 및 열 발생 경향성을 유한요소 해석법으로 해석하였다. 나아가 해석되어진 결과를 바탕으로 최대 음압을 구현하고, 열 발생이 최소인 중심 주파수 1 kHz를 가지는 Class W Flextensional 트랜스듀서의 최적구조를 설정하였다. 본 연구에서 설정한 최적구조는 기본모델에 비해 음압이 2배 이상 크고, 열 발생은 아주 작은 것으로 나타났다. 본 연구의 결과는 향후 다양한 중심 주파수 및 최대 음압을 구현하고 열 발생이 최소인 Class W Flextensional 트랜스듀서를 설계함에 있어 유용한 자료로 활용될 수 있을 것이다.

• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.368-374
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• 2016

This paper presents constructing transmitter and receiver by using a direct sequence spread spectrum techniques to DPSK (Differential Phase-Shift Keying) scheme in underwater acoustic communication. Since DPSK signal can be demodulated if the receiver knows only the phase difference between the adjacent bits, DPSK receiver structure has the advantage of being simplified. In the conventional receiver, two adjacent symbols of transmitted signal before despread are passed to the transition correlator that detects data by comparing maximum correlation outputs. At this time, the error for maximum value of the correlator output may increase because of low SNR (Signal to Noise Ratio) or high Doppler shift frequency according to the underwater channel. In this paper, we propose a method for accurate detection result using the width as well as the magnitude among outputs produced by the correlator. The performances of the proposed method was evaluated by simulation and lake trial data.

• The Journal of the Acoustical Society of Korea
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• v.16 no.2
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• pp.5-9
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• 1997

In this paper, when we use the chirp signal as input signal of ultrasonic signal system the technique for determining the bandwidth of the chirp signal that maximizes the amplitude of the compressed ultrasonic echo signal has been studied. In ultrasonic signal processing systems, the signal-to-noise ratio of the echo signal can be too low due to damping and scattering of the ultrasonic wave during transmission. Method of pulse compression using chirp signal is a means to increase the signal-to-noise ratio in ultrasonic pulse-echo systems. Simulation and experimental results showed that the output signal of ultrasonic system was increased by pulse width of chirp signal and the optimum-bandwidth of the chirp signal was 1.15 times larger than the bandwidth of the ultrasonic system.

• The Journal of the Acoustical Society of Korea
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• v.31 no.5
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• pp.280-287
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• 2012

This paper presents a study on the experimental analysis of the impedance characteristics according to the rotational direction of the transmission beam of a cylindrical sensor array. Besides, this suggests a real time control technique of the transmitter output for the effective maximum power transmission, in order to drive efficiently the rotational transmission beam of the active sonar transmitter. The output characteristics of the transmitter and the real-time impedance variations of the sensor array are analyzed under the overload conditions. They are caused by electric and acoustic boundary conditions when the rotational transmission beam is operated. From these results, a new output control method of the transmitter is proposed to protect the transmitter and its loads. It can maximize the output power without the transmission pause even if the transient phenomena occur. The proposed technique is verified from the experiment.

• The Journal of the Acoustical Society of Korea
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• v.40 no.3
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• pp.241-246
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• 2021

Modern loudspeaker systems are changing an active loudspeaker system that have multiple input channels and power amplifier. So, we cannot measure these active loudspeakers with IEC 60268-5 standard. This paper introduces an IEC 60268-21 standard that can measure an active loudspeaker having many analog and digital and wireless or wired inputs and having various control parameters.