• Title, Summary, Keyword: Two-Microphone Method

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The Limit and Application of Two-microphone Impedance Tube Method to the Sound Transmission Loss Measurement of Sound Isolation Materials (차음재의 음향투과손실 측정에 Two-Microphone Impedance Tube Method의 적용과 한계)

  • Lee, Seung;Ahn, Min-Hong;Lee, Dong-Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.883-888
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    • 2002
  • This study describes the limit and application of the two-microphone impedance tube method to the sound transmission loss measurement of several sound isolation materials with different physical properties. For the sound isolation materials having small flexural rigidity, it is shown that the two-microphone impedance tube method is validated to practically measure the sound transmission loss. For the sound isolation materials having large flexural rigidity, on the other hand, it is found that the two-microphone impedance tube method is no longer valid to measure the sound transmission loss because the regions of resonance and mass law are moved into the higher frequencies. In addition, in order to accurately measure the sound transmission loss of sound isolation materials, their size should be decided based on the consideration of the effect of acoustic excitation on their vibration response.

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A TDOA Sign-Based Algorithm for Fast Sound Source Localization using an L-Shaped Microphone Array

  • Yiwere, Mariam;Rhee, Eun Joo
    • Journal of Information Technology Applications and Management
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    • v.23 no.3
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    • pp.87-97
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    • 2016
  • This paper proposes a fast sound source localization method using a TDOA sign-based algorithm. We present an L-shaped microphone set-up which creates four major regions in the range of $0^{\circ}{\sim}360^{\circ}$ by the intersection of the positive and negative regions of the individual microphone pairs. Then, we make an initial source region prediction based on the signs of two TDOA estimates before computing the azimuth value. Also, we apply a threshold and angle comparison to tackle the existing front-back confusion problem. Our experimental results show that the proposed method is comparable in accuracy to previous three microphone array methods; however, it takes a shorter computation time because we compute only two TDOA values.

Multiple Microphone Technique for a Direct Measurement of In-duct Acoustical Parameters (다수의 마이크를 이용한 관내 음향 변수의 직접 측정법)

  • Jang, Seung-Ho;Ih, Jeong-Guon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.1661-1666
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    • 2000
  • Nowadays, the two microphone method is accepted as the standard as specified in ASTM E1050-90 for measuring in-duct acoustic properties. However, research results on using the least square method with multiple measurement points and broadband excitation have been reported for enhancing the frequency response of the two microphone method. In this paper, the effects of varying the relative measurement positions on errors in the estimation of the acoustic quantities is studied for the multiple microphone method. Both of the theoretical and experimental results show that, among every possible sensor positioning configurations, the equidistant positioning of sensors yields the smallest error within the effective measurement frequency range. In addition, it is noted that the measurement accuracy can be increased and the effective frequency range can be widened by increasing the number of equidistant sensors. Measurement examples are shown and the results support the findings.

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A study of transmission loss and surface vibration mode by the two microphone acoustic intensity method (음향강도계측법에 의한 음향투과손실의 측정 및 표면진동 모우드의 예측에 관한 연구)

  • 김의간;남청도;전효중
    • Journal of Advanced Marine Engineering and Technology
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    • v.11 no.1
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    • pp.63-71
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    • 1987
  • The measuring of acoustic intensity has been investigated by many researchers and practicians during the last several decades. But due to the lack of measurement accuracy, they have had no practical use. In recent years, the two microphone acoustic intensity method has been developed by the advancement of FFT analysis technique and the digital data processing equipment. This new method of using two microphones gives informations on the noise source survey and the acoustic power of sound radiation source without the anechoic room. In this paper, theoretical formulae for the two microphone acoustic intensity method and the sound transmission loss are checked. The obtained results for the acoustical enclosure of gas heat pump were compared with the classical field incidence mass law. The surface vibration modes for a panel of enclosure were also estimated.

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Improvement Method and Experiment Analysis of Sniper Distance Estimation Using Linear Microphone Array (선형마이크로폰 어레이를 이용한 저격수 거리추정 개선방법과 실험 분석)

  • Jung, Seungwoo
    • Journal of the Korea Institute of Military Science and Technology
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    • v.21 no.4
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    • pp.447-455
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    • 2018
  • If a hidden enemy is shooting, there is a threat against soldiers in recent conflicts. This paper aims to improve the localization of a muzzle using microphone array. Gunshot noise can provide information about the location of muzzle with two signals, the muzzle blast from the gun barrel and the projectile sound from the bullet. Two signals arrive to the microphone array with different arrival time and angle. If the arrival angles of the two signals are estimated, distance between sniper location and the microphone array can be calculated by using geometric principles. This method was established in 2003 by Pare. But this method has a limitation that it cannot calculate the distance when the arrival angles of the two signals are same. Also it has an error when the angle difference of arrival is small. In order to overcome this limitation, a new method is proposed that uses the change of characteristic of the projectile sound with respect to vertical distance from the trajectory. The proposed method estimates the distance correctly when the arrival angle of two signals are same, and when the angle difference between two signals is increased, the estimation error increases with respect to the angle. Therefore these two methods can be selected according to the angle difference between two signals to estimate the distance of the muzzle. Below the threshold of the angle difference, the proposed method can be used to estimate distance with smaller error than the existing method. This was demonstrated by shooting tests using actual sniper rifles.

Sound Transmission Loss Measurement for Sound Isolation Sheets by Two-Microphone Impedance Tube Method (두 개의 마이크로폰의 부착된 임피던스관법을 이용한 차음시트의 음향투과손실 측정)

  • Lee, Dong-Hoon;Yong, Ho-Taek;Lee, Seung
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.1
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    • pp.63-72
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    • 2002
  • 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.

Measurement of the Sound Absorption Coefficient of Fiberboard by Two Microphone Method

  • Kang, Chun Won;Park, Hee Jun;Jeong, In Soo;Kim, Gwang Chul
    • Journal of the Korean Wood Science and Technology
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    • v.33 no.5
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    • pp.45-49
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    • 2005
  • The sound absorption coefficients of three types commercial fiberboard were experimentally measured under a relatively low frequency range of 50 to 1600 Hz by the two microphone transfer function method. The sound absorption coefficient of 30 mm thick fiberboard was higher than that of 18 mm thick fiberboard at the frequency range of 50 to 1.2 KHz. The sound absorption coefficient of medium density fiberboard was a little higher than that of low density fiberboard.

A Study on the Sound Transmission Loss Measurement of Sound Isolation Sheets (차음시트의 음향투과손실 측정에 관한 연구)

  • Lee, Dong-Hoon;Kang, Moon;Lee, Ju-Weon;Jung, Gab-Cheol;Kwon, Young-Pil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.409-414
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    • 2000
  • A new impedance tube method is presented for the measurement of transmission loss of sound isolation sheets. The two-microphone method based on the sound decomposition theory proposed by Seybert and Ross is reviewed in this impedance tube method, which has been used for the determination of absorption coefficient of absorptive materials as well as transmission loss of automotive mufflers. Sound transmission losses for rubber, polyvinyl and asphalt sheets are measured in an impedance tube and reverberation room facility, respectively. By comparing two measurement methods, the reliability of impedance tube method used in this study is validated. From the experimental results, it is shown that the accuracy of sound isolation capability obtained by the impedance tube method depends upon the microphone spacing and the distance of the first microphone from the test sample surface.

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A User-friendly Remote Speech Input Method in Spontaneous Speech Recognition System

  • Suh, Young-Joo;Park, Jun;Lee, Young-Jik
    • The Journal of the Acoustical Society of Korea
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    • v.17 no.2E
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    • pp.38-46
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    • 1998
  • In this paper, we propose a remote speech input device, a new method of user-friendly speech input in spontaneous speech recognition system. We focus the user friendliness on hands-free and microphone independence in speech recognition applications. Our method adopts two algorithms, the automatic speech detection and the microphone array delay-and-sum beamforming (DSBF)-based speech enhancement. The automatic speech detection algorithm is composed of two stages; the detection of speech and nonspeech using the pitch information for the detected speech portion candidate. The DSBF algorithm adopts the time domain cross-correlation method as its time delay estimation. In the performance evaluation, the speech detection algorithm shows within-200 ms start point accuracy of 93%, 99% under 15dB, 20dB, and 25dB signal-to-noise ratio (SNR) environments, respectively and those for the end point are 72%, 89%, and 93% for the corresponding environments, respectively. The classification of speech and nonspeech for the start point detected region of input signal is performed by the pitch information-base method. The percentages of correct classification for speech and nonspeech input are 99% and 90%, respectively. The eight microphone array-based speech enhancement using the DSBF algorithm shows the maximum SNR gaing of 6dB over a single microphone and the error reductin of more than 15% in the spontaneous speech recognition domain.

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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
    • International Journal of Air-Conditioning and Refrigeration
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    • v.11 no.3
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    • pp.105-113
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    • 2003
  • 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.