• Title/Summary/Keyword: Sound Pressure

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Designing Flexible Thin Film Audio Systems Utilizing Polyvinylidene Fluoride

  • Um, Keehong;Lee, Dong-Soo;Pinthong, Chairat
    • International journal of advanced smart convergence
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    • v.2 no.2
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    • pp.16-18
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    • 2013
  • In this paper, we develop a method to design a flexible thin film audio systems utilizing Polyvinylidene fluoride. The system we designed showed the properties of increased transparency and sound pressure levels. As an input terminal transparent oxide thin film is adopted. In order to provide dielectric insulation, a transparent insulating oxide thin film is coated to obtain double -layered structure. In the range of visible light, the output from the output of the system showed an increased and improved sound pressure level. The piezoelectric polymer film of polyvinylidene fluoride (PVDF) is used to produce mechanical vibration due to the applied electrical voltage signal. An analog electric voltage signal is transformed into sound waves in the audio system.

Study on low frequency swishing sound field by singularities in circular motion with large radius (큰 반경의 원운동을 하는 점 음원에 의한 저주파수 스위싱 음장 분석)

  • Lee, Gwang-Se;Cheong, Cheolung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.04a
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    • pp.90-95
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    • 2014
  • In order to investigate low frequency swishing noise of wind turbines, singularity in circular motion with large radius is introduced as a noise source model. By employing Lowson's acoustic analogy, simple exact solution is obtained. The solution shows that time histories of acoustic pressure at receiver points varied significantly according to receiver's directional location, even when the retarded time distributions are similar. However, the corresponding spectra of sound pressure for the receiver locations where the retarded time distributions are almost the same are not significantly different. It can be inferred from these results that the time-averaged sound pressure spectra which cannot take into account the detailed difference in the time-variation of wind turbine noise may not represent the sound quality of wind turbines due to its swishing.

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Direct Simulation of Acoustic Sound by the Finite Difference Lattice Boltzmann Method (차분격자볼츠만법에 의한 유체음의 직접계산)

  • Kang, Ho-Keun;Ro, Ki-Deok;Lee, Young-Ho
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.1827-1832
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    • 2003
  • In this research, the simulation method for acoustic sounds by a uniform flow around a two-dimensional circular cylinder by using the finite difference lattice Boltzmann model is explained. To begin with, we examine the boundary condition which determined with the distribution function $f_i^{(0)}$ concerning with density, velocity and internal energy at boundary node. Very small acoustic pressure fluctuation, with same frequency as that of Karman vortex street, is compared with the pressure fluctuation around a circular cylinder. The acoustic sound' propagation velocity shows that acoustic approa ching the upstream, due to the Doppler effect in the uniform flow, slowly propagated. For the do wnstream, on the other hand, it quickly propagates. It is also apparently the size of sound pressure was proportional to the central distance $r^{-1/2}$ of the circular cylinder. The lattice BGK model for compressible fluids is shown to be one of powerful tool for simulation of gas flows.

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Definition and Improvement of the Sound which was Generated by Bubbles at the Accumulator of the Evaporator (증발기 어큐뮤레이터에서의 버블 소음 규명 및 개선)

  • 박정희;장의영;박윤서
    • Journal of KSNVE
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    • v.6 no.4
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    • pp.513-519
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    • 1996
  • This paper is concerned with the bubble sound at the accumulator which is generated by the difference of the high pressure side and the low pressure side in the cycle of the refrigerator. The causes of the bubble sound generation are verified by the visualized test of the operating refrigerant flow at the accumulator and the measurements of the temperature and pressure. Two cases were tested, one with the accumulator has a orifice and the other with the accumulator hasn't a orifice. So that, it is presented the comparison of the bubble sound levels and spectrums in each cases. To predict the bubble sizes when they are generated, the linearized equation driven by Strasberg is used.

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Designing Piezoelectric Audio Systems Using Polymer Polyvinylidene Fluoride

  • Um, Keehong;Lee, Dong-Soo;Pinthong, Chairat
    • International Journal of Internet, Broadcasting and Communication
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    • v.6 no.1
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    • pp.13-15
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    • 2014
  • We develop a method to fabricate a flexible thin film audio systems using polyvinylidene fluoride(PVDF). The system we designed showed the properties of increased flexibility, transparency, and sound pressure levels. As an input port of two terminals, transparent oxide thin film with a low resistivity is adopted. In order to provide dielectric insulation, a transparent insulating oxide thin film is coated to obtain double-layered structure. In the range of visible light, the output from the output of the system showed a increased and improved sound pressure level. The piezoelectric polymer film of PVDF is used to produce mechanical vibration due to the applied electrical voltage signal. An analog electric voltage signal is transformed into sound waves in the audio system.

Comparative Analysis on the Sound Characteristics of Riffles and Pools (여울과 소의 소리특성 비교 분석)

  • Kang, Su-Jin;Kang, Joon-Gu;Kim, Jong-Tae
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.12
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    • pp.878-886
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    • 2018
  • This study quantified the sounds of riffles and pools in natural rivers and conducted a comparative analysis of the frequency and sound pressure per flow velocity. The surveyed area was Namdaecheon basin in Yangyang-gun, Gangwon-do and the sounds of a total of 23 sites were analyzed. A hydro microphone was used to measure the sound and analyze the data using an acoustic analysis program. The location was also selected at places with minimal ambient noise and the measurement points were the depth of riffles and pools. The results revealed an average difference of 0.515 m/s for flow velocity at 8 riffles and 15 pools. The difference in sound pressure occurred due to the flow velocity. In the case of sound pressure, it was measured at an average of 176.8 dB for riffles and 168.2 dB for pools, demonstrating a difference of approximately 8.6 dB. Furthermore, in the case of maximum sound pressure, riffles showed a constant range between 200 Hz and 250 Hz, while the pools exhibited maximum sound pressure at various frequencies from 200 Hz to 1,000 Hz. This revealed the ecological stream reproduction, development of preferred sound sources for aquatic life, and design of structures.

A Study on the Optimized Announcement Based Evacuation Guidance Using Haas Effect (선행음 효과를 이용한 최적의 음성피난유도음에 관한 연구)

  • Baek, Eun-Sun;Kim, Sun-Woo;Baek, Geon-Jong;Shin, Hoon;Song, Min-Jeong;Kook, Chan
    • Fire Science and Engineering
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    • v.25 no.2
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    • pp.101-106
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    • 2011
  • In case of an emergency such as a fire on a building and there is a need to evacuate the occupant in that building, it is important to have the guidance information effectively delivered to the evacuating occupants to guide them toward a safe direction using audio sensual media. And, it is also very important to prevent the evacuating occupants getting lost or falling astray, away from the direction toward safety. The purpose of this study, in this respect, is to examine the possible application of the precedent sound effect, with which the evacuating occupants may get a sense of the direction where the announcement comes from. With such an effect, an experiment was conducted to measure the extent to which people can hear the preceding and the following sound in terms of the acoustic pressure level changes and delay time changes, with a view to make the optimal evacuation-guidance announcement or sound. The optimal evacuation guidance sound (announcement) per each of the experimental indoors environments were as follows; 1) Regarding the optimal condition for the evacuation guidance announcement sound in the space of a lecture room, the direction of the advanced sound is positively recognized when the follow-up sound has the delaying time of 10 ms~50 ms in comparison with the advanced sound or when there is no difference between the acoustic pressures of the advanced and follow-up sounds or the acoustic pressure of the advanced sound is higher than that of the follow-up sound. 2) Regarding the optimal evacuation guidance announcement sound in the space of a hall, the advanced sound is positively recognized when the follow-up sound has the delaying time of 20 ms~60 ms in comparison with the advanced sound. 3) Regarding the optimal evacuation guidance announcement sound in the space of a gymnasium, the advanced sound is positively recognized when the follow-up sound has the delaying time of 10 ms~40 ms in comparison with the advanced sound or when the sound pressure of the advanced sound has a higher level than or the same level as that of the follow-up sound.

An analysis of acoustic pressure in the center of double pipe inside of a cylindrical vibrator (원통형 진동자 내부의 이중관 중심에서의 음압해석)

  • Kim, Jungsoon;Kim, Moojoon
    • The Journal of the Acoustical Society of Korea
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    • v.36 no.3
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    • pp.165-171
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    • 2017
  • The effect of the concentric solid tube inserted inside the vibrator on the sound field distribution was analyzed for the sound waves focused on the center axis in the fluid - filled cylindrical piezoelectric transducer. The sound waves radiated from the inside of the cylindrical piezoelectric vibrator are transmitted through the fluid medium and are reflected or transmitted on the wall surface of the solid tube, and are focused on the central axis. At this time, the sound field distribution centered on the acoustic tube varies depending on the acoustic impedance and the thickness of the solid tube. In order to theoretically analyze this, the transfer matrix for each medium is derived, and the sound pressure level at the center axis is theoretically analyzed. For the acrylic tube with various thicknesses, the changing trend in the sound pressure level measured on the central axis agrees well with the result of the theoretical analysis, and it confirmed that the sound pressure formed at the center changes very sensitively with the thickness of the solid tube.

Compensation of low Frequency Resonance in Current Driven Loudspeakers using DSP (DSP를 이용한 전류구동 스피커의 저주파 공진 보상)

  • Park, Jong-phil;Eun, Changsoo
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2021.05a
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    • pp.584-588
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    • 2021
  • The impedance of the speaker is likely to be recognized as a fixed value. However, speaker impedance continues to vary with frequency variation, especially larger in resonant frequency region. The sound pressure level of loudspeakers is determined by the current flowing throughout the coil that consists loudspeakers. If loudspeakers are driven by voltage, sound pressure level of the loudspeaker is distorted by the variation of loudspeaker impedance. Current-drive of loudspeakers can solve this problem, but distortion of sound pressure level occurs in low frequencies due to resonance. The distortion can degrade the sound quality of the sound system. So to solve this problem, In this paper, we propose a resonance compensation circuit using DSP. we simulates audio systems using an equivalent model of loudspeakers to verify distortion of sound pressure level due to impedance variation and propose a circuit to compensate it. The proposed circuit is configured using a state variable filter and it can adjust the center frequency and output, so it will be used various sound systems.

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A Study of Enemy Aptitude of Pistol Sound Source for Space Estimation (공간평가를 위한 피스톨음원의 적정성에 관한 연구)

  • Shon, Jang-Ryul;Kim, Jung-Joong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.3 s.96
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    • pp.320-328
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    • 2005
  • Last target of architectural acoustics is that people wish to convey voice effectively from the space adaptively in use purpose in building. But, how exactly through space sound (sound source) that wish to deliver from indoor can be passed method to do quantification and evaluate quantity of sound by method to serve indoor architectural acoustics estimation summer period and methods to estimate definition propose. This Study searches special quality of sound source about MLS signal that is occurred short-answer sound source (pistol sound source) and nondirectional speaker among indoor sound estimation method, and measure and analyzed reverberation time (RT60), definition (C80, D50) by regulation of each ISO 3382 in age place (classroom, hall, gymnasium). Analysis result and sound factor among could know that d of two sound sources converges in measurement error extent about reverberation time (RT60) of analysis incidental and sound factors and value shows change irregularly about sound factor of D50, C80, pistol sound source judged there is problem. Also, could know that problem is happened in deflection except reverberation time is in deflection analysis with wave that measure each in fixed distance in branch. Finally, when differ size of sound source and measure about change of sound pressure level in case measure sound pressure level giving difference about 10 dB, sound factor could know that there is no different effect.