• Title/Summary/Keyword: acoustical coefficient

Search Result 212, Processing Time 0.04 seconds

Effects of Double Surfaces Finishing on Acoustical Properties of Soundboard for Traditional Musical Instruments (전통악기 음향판의 양면도장이 음향성에 미치는 영향)

  • Jung, Hee-Suk;Yoo, Tae-Kyung;Kwon, Joo-Yong
    • Journal of the Korean Wood Science and Technology
    • /
    • v.26 no.4
    • /
    • pp.26-33
    • /
    • 1998
  • Acoustical properties of chestnut and paulownia woods have been determined in four film thicknesses of oriental lacquering and cashew varnishing on double surfaces of soundboard to elucidate effects of finishing. Accelerometer was attached to the specimen at one third position from one end, and specimen was hit by the impact hammer at one third position from opposite end. Data were processed by vibration analyzer. The ratio of axial-to-transverse sound velocity of untreated specimens of chestnut and paulownia were 3.25 and 5.34, respectively. Natural frequency, specific Young's modulus, acoustical coefficient, sound velocity, damping of sound radiation(DSR) and acoustical converting efficiency(ACE) decreased by oriental lacquering and cashew varnishing for both species. Damping of internal friction of chestnut decreased by oriental lacquering and cashew varnishing, but that of paulownia increased. Natural frequency. specific Young's modulus, acoustical coefficient, sound velocity, and DSR decreased with increased film thickness of both finishing materials. However, damping of internal friction and ACE showed irregular tendency with increased film thickness. Acoustical properties of cashew varnished chestnut specimen were better than those of oriental lacquered specimen. Acoustical properties of oriental lacquered paulownia specimen were better than those of cashew varnished specimen.

  • PDF

On the Transmission Loss Measurement System (전달손실계수 측정 시스템에 대하여)

  • Ryu, Yun-Seon;Kim, Yoon-Seok;Callec, Philippe
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2002.11b
    • /
    • pp.166-171
    • /
    • 2002
  • The transmission loss coefficient is very important acoustic property in parallel with absorption and acoustic impedance categorizing the acoustical materials, which can control the acoustical problems. At the same time, the transmission loss coefficient is a key parameter to choose the optimum material for the analysis of acoustical characteristics of material using SEA(Statistical Energy Analysis). In this paper, the transmission loss coefficient measurement system using 4-microphone impedance tube is proposed, based on the idea calculating the full transfer matrix of the acoustical sample to test. The theoretical background and measurement system are introduced, and finally the measurement results are verified.

  • PDF

On the Transmission Loss Measurement System (전달손실계수 측정시스템에 대하여)

  • Yunseon RYU;Yoon-Seok KIM;Philippe CALLEC
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2002.11a
    • /
    • pp.323.1-323
    • /
    • 2002
  • The transmission loss coefficient is very important acoustic property in parallel with absorption and acoustic impedance categorizing the acoustical materials, which can control the acoustical problems. At the same time, the transmission loss coefficient is a key parameter to choose the optimum material for the analysis of acoustical characteristics of material using SEA(Statistical Energy Analysis). In this paper, the transmission loss coefficient measurement system usiong 4-microphone impedance tube is proposed, based on the idea calculating the full transger matrix of the acoustical sample to test. The theoretical backgroung and measurement system are introduced, and finally the measurement results are verified.

  • PDF

On the Transmission Loss Measurement System(Part II) (전달손실계수 측정 시스템에 대하여(Part II))

  • 김윤석;류윤선
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2003.05a
    • /
    • pp.658-661
    • /
    • 2003
  • The transmission loss coefficient is very important acoustic property in parallel with absorption and acoustic impedance categorizing the acoustical materials, which can control the acoustical problems. At the same time, the transmission loss coefficient is a key parameter to choose the optimum material for the analysis of acoustical characteristics of material using SEA(Statistical Energy Analysis). In this paper, the transmission loss coefficient measurement system using 4-microphone impedance tube is proposed, based on the idea calculating the full transfer matrix of the acoustical sample to test. The theoretical background and measurement system are introduced, and finally the measurement results are verified.

  • PDF

Acoustic Transmission Loss Measurement of the Exhaust System with TL Tube (TL 튜브를 이용한 소음기의 음향 전달 손실 계측법)

  • 류윤선;김윤석;이성홍
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2004.05a
    • /
    • pp.770-773
    • /
    • 2004
  • The transmission loss coefficient is very important acoustic property in parallel with absorption and acoustic impedance categorizing the acoustical materials, which can control the acoustical problems. At the same time, the transmission loss coefficient is a key parameter to choose the optimum material for the analysis of acoustical characteristics of material using SEA(Statistical Energy Analysis). In this paper, the acoustic transmission loss measurement system using 4-microphone TL tube is applied to the exhaust system, which is one of the most important acoustic control parameters in a car, based on the idea calculating the full transfer matrix. The theoretical background and measurement system are introduced, and finally the measurement results are verified.

  • PDF

Measurements of Scattering Coefficients Using the ISO Method in a Model Reverberation Chamber (ISO 방법론을 이용한 축소 잔향실에서의 확산계수 측정)

  • 전진용;이성찬;류종관
    • The Journal of the Acoustical Society of Korea
    • /
    • v.22 no.3
    • /
    • pp.162-168
    • /
    • 2003
  • The degree of diffusion, characterized by the "scattering coefficient" of surface materials, has been known to be one of the most important factors in determining the acoustical qualities of concert halls. Based on the suggested ISO method, which measures the random-incidence scattering coefficient of surfaces in a diffuse field, the scattering coefficients of different sizes and densities of wooden hemispheres and cubes were measured in model-scale reverberation rooms. As a result, wooden hemispheres with a structural depth of more than 15㎝ have the highest average (500㎐∼4㎑) scattering coefficient. It was also found that the scattering coefficient becomes higher when the diffuser density reaches about 50% for hemispheres and 30% for cubes.

Performance Evaluation and Convergence Analysis of a VEDNSS LMS Adaptive Filter Algorithm

  • Park, Chee-Hyun;Hong, Kwang-Seok
    • The Journal of the Acoustical Society of Korea
    • /
    • v.27 no.2E
    • /
    • pp.64-68
    • /
    • 2008
  • This paper investigates noise reduction performance and performs convergence analysis of a Variable Error Data Normalized Step-Size Least Mean Square(VEDNSS LMS) algorithm. Adopting VEDNSS LMS results in higher system complexity, but noise is reduced providing fast convergence speed Mathematical analysis demonstrates that tap coefficient misadjustment converges. This is confirmed by computer simulation with the proposed algorithm.

An acoustical characteristics of sound proof panel for high speed train (고속전철용 방음패널의 음향특성 평가)

  • 서재갑;정성수;서상준;조문재;나희승;양신추
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2001.11a
    • /
    • pp.145-149
    • /
    • 2001
  • In this study, an acoustical characteristics of sound proof panel for high speed train was performed. A sound absorption coefficient and transmission loss of sound proof panels for high speed train were tested in reverberation chambers and compared those of ordinary sound proof panel. The effect of noise barrier was simulated by using ray noise program with measured sound absorption coefficient for high speed train case and for ordinary case.

  • PDF

Determination of a New Cut-off Frequency Coefficient for Sound Propagation in the Surface Duct (표층도파관 내에서의 새로운 Cut-off 주파수 계수결정)

  • 김성부
    • The Journal of the Acoustical Society of Korea
    • /
    • v.1 no.1
    • /
    • pp.37-44
    • /
    • 1982
  • In the mixed layer when the frequency approaches the cut-off frequency for the first mode of notmalmode theory, sound ceases to be trapped. Based on the data of surface sound velocities abtained during the period of 16 years in the Sea of Japan. A new cut-off frequency coefficient in the surface duct that will determine the miximum wave length for duct transimission of underwater sound has been calculated.

  • PDF

Experimental Verification of the Unified Formula for Electromechanical Coupling Coefficient of Piezoelectric Resonators

  • Kim, Jung-Soon;Kim, Moo-Joon;Ha, Kang-Lyeol;Cao, Wen-Wu
    • The Journal of the Acoustical Society of Korea
    • /
    • v.25 no.3E
    • /
    • pp.110-114
    • /
    • 2006
  • In a previous theoretical paper, we have derived a unified formula by considering 2-D coupled mode vibrations. The unified formula for electromechanical coupling coefficient of piezoelectric resonator was verified experimentally. The capacitance change near the resonant frequency was investigated to estimate the effective coupling coefficient of the resonator instead of the conventional method based on I-D model. The susceptance spectra were measured for the seven samples of piezoelectric resonator with different aspect ratio. Excellent agreement between theoretical and experimental results was obtained.