• Title, Summary, Keyword: Acoustic reciprocity

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Noise Estimation in a Passenger Compartment and Trunk Coupled System by Using the Vibro-Acoustic Reciprocity (진동-음향 상반성을 이용한 차실-트렁크 연성계의 소음평가)

  • 이진우;이장무;김석현;박동철
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.6
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    • pp.178-185
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    • 2001
  • This paper describes the correlation between the interior noise and the trunk wall vibration. Using the vibro-acoustic reciprocity, effect of the trunk wall vibration on the compartment noise is investigated on a medium size car. In the low frequency range, vehicle interior noise is dominated by several acoustic modes of the passenger compartment and the vibration modes of the surrounding shell parts. Especially, vibration of the trunk wall radiates sound and it is transferred through holes on the package tray into the passenger compartment. This paper experimentally reveals that sound can be well produced at some particular vibration modes of the trunk lid and it strongly influences the compartment noise through package tray holes. Contributions of the trunk walls to the interior noise are estimated by measuring the acoustic-structural transfer function, based on the vibro-acoustical reciprocity theorem.

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Noise Estimation in a Passenger Compartment and Trunk Coupled System by Using the Vibro-Acoustic Reciprocity (진동-음향 상반성을 이용한 차실-트렁크 연성계의 소음평가)

  • Lee, Jin-Woo;Lee, Jang-Moo;Kim, Seock-Hyun;Park, Dong-Chul
    • Proceedings of the KSME Conference
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    • pp.618-622
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    • 2000
  • This paper describes the correlation between the interior noise and the trunk wall vibration. Using the vibro-acoustic reciprocity, effect of the trunk wall vibration on the compartment noise is investigated on a medium size car. In the low frequency range, vehicle interior noise is dominated by several acoustic modes of the passenger compartment and the vibration modes of the surrounding shell parts. Especially, vibration of the trunk wall radiates sound and it is transferred through holes on the package tray into the passenger compartment. This paper experimentally reveals that sound can be well produced at some particular vibration modes of the trunk lid and it strongly influences the compartment noise through package tray holes. Contributions of the trunk walls to the interior noise are estimated by measuring the acoustic-structural transfer function, based on the vibro-acoustical reciprocity theorem.

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NEW TECHNIQUE IN THE USE OF VIBRO-ACOUSTICAL RECIPROCITY WITH APPLICATION TO THE NOISE TRANSFER FUNCTION MEASUREMENT

  • Ko, K.H.;Kook, H.S.;Heo, S.J.
    • International Journal of Automotive Technology
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    • v.7 no.2
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    • pp.173-177
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    • 2006
  • A noise transfer function(NTF) is the frequency response function between an input force applied to an exterior point of a vehicle body and the resultant interior sound pressure usually measured at the driver's ear position. It represents the measure of noise sensitivity for the output force transmitted to the joints between the body and chassis. The principle of vibro-acoustic reciprocity is often utilized in the measurement of NTF. One difficulty in using the volume source is that most of the previously proposed methods require the knowledge of the volume velocity of the acoustic source in advance. A new method proposed in the present work does not require any calculation related with the volume velocity of the acoustic source, but still yields even more accurate results both in the amplitude and phase of the NTF. In the present work, the new method is applied to obtain NTF data for a midsize sedan.

Measurement of Mechanical-acoustic Transfer Functions of Vehicles by Combination of Mechanical and Acoustic Excitations (구조가진과 음향 가진의 결합에 의한 차량의 구조-음향 전달 함수 측정)

  • 고강호;이장무
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.9
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    • pp.158-164
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    • 1999
  • In this paper a simple measurement technique for mechanical-acoustic transfer functions is proposed . The mechanical-acoustic transfer functions, generally , are measured through mechanical excitations ; impact hammers or shakers. Recently , by virtue of vibro-acoustical reciprocity principle, they are measured through acoustic excitations : loudspeakers. This kind of test needs to measure the volume velocity , the radiation characteristics of a sound source. Because the volume velocity of the sound source is changed by driving signal , it is difficult to measure it. However , the new method in this paper needs not to measure the volume velocity of a sound source by combination of mechanical and acoustic excitations. Moreover, this method has the methodological advantages, such as usage of a general loudspeaker for the reciprocal excitation, no sptatial limitations for measurements of mechanical-acoustic transfer functions.

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The Analysis of Vehicle Interior Noise by the Powertrain, and Measurement of Noise Trasnsfer Function using Vibro-Acoustic Reciprocity (파워트레인에 의한 차량 실내 소음 특성 및 전달 함수 측정)

  • Kim, Sung-Jong;Lee, Sang-Kwon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.501-506
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    • 2007
  • Structure-borne noise is the interior noise that results from the low frequency vibrational energy transmitted through those body and joint parts. The relation between the excitation of powertrain and resultant interior sound must be analyzed in order to identify and predict the structure borne noise. The method of acoustic source excitation is preferred than the method of mechanical force excitation to measure the NTF(noise transfer function). Because acoustical method is more convenient and reliable. In this paper, to analysis and identify vehicle interior noise by powertrain is performed, and the vibro-acoustic transfer function is extracted from experimental measurement. These are important step of TPA(transfer path analysis) to identify effect of interior noise resulted from powertrain running excitation.

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The Application of Equivalent Area to the Volume Velocity for Using the Vibro-acoustical Reciprocity (진동-음향 상반 원리에 이용되는 음원의 유효 면적 측정)

  • 고강호
    • Journal of KSNVE
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    • v.9 no.5
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    • pp.943-948
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    • 1999
  • This paper proposes a feasible and effective method for measuring the mechanical-acoustic transfer function by the application of equivalent area and velocity transfer function, a manifestation of the vibro-acoustical reciprocity principle. On the contrary to the volume velocity used in traditional method, the equivalent area is a peculiar raidation characteristics of sound sources and not influenced by any input signal for driving sound source. This invariant property of equivalent area can get rid of boresome works to measure the volume velocity of a sound source every time the driving signal is changed. Moreover, this method has a remarkable advantage to use a general loudspeaker as an accoustic exciter without the assumption of point source and can be applied to all kinds of sound sources even if they are not omni-directional sources.

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The Electro-Mechanical Signal Transformation of Piezo-Electric Transducer (압전식 탐촉자의 기계-전기 신호 변환)

  • Ahn, Tae-Won
    • Journal of the Korean Society for Nondestructive Testing
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    • v.20 no.2
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    • pp.110-115
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    • 2000
  • The electromechanical reciprocity identity is introduced to relate the voltage at the terminals of a transducer to the acoustic wavefields scattered from the specimen. The voltage at the terminals of the transducer is expressed as an integral equation in terms of the displacement and stress of the incident and scattered waves on the closed surface enclosing the scatterer. The equation is used to relate the voltage at the terminals of an acoustic microscope's transducer to the acoustic wavefields at the interface between the specimen and the coupling fluid. The voltage calculated using the integral equation is compared with the experimental result.

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Road Noise Prediction Based on Frequency Response Function of Tire Utilizing Cleat Excitation Method (크리트 가진법을 이용한 타이어특성에 따른 로드노이즈 예측 연구)

  • Park, Jong-Ho;Hwang, Sung-Wook;Lee, Sang-Kwon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.8
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    • pp.720-728
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    • 2012
  • It is important for identification of noise and vibration problem of tire to consider influence of interaction between road and tire. A quantification of road noise is a challenging issue in vehicle NVH due to extremely complicated transfer paths of road noise as well as the difficulty in an experimental identification of input force from tire-road interaction. A noise caused by tire is divided into road noise(structure-borne noise) and pattern noise(air-borne noise). Pattern noise is caused by pattern shape of tire, which has larger than 500 Hz, but road noise is generated by the interactions between a tire and a vehicle body. In this paper, we define the quantitative analysis for road noise caused by interactions between tire and road parameters. For the identification of road noise, the chassis dynamometer that is equipped $10mm{\times}10mm $ square cleat in the semi-anechoic chamber is used, and the tire spindle forces are measured by load cell. The vibro-acoustic transfer function between ear position and wheel center was measured by the vibro-acoustic reciprocity method. In this study three tires with different type of mechanical are used for the experiment work.

The Use of Vibro-acoustical Reciprocity to Estimate Source Strength and Airborne Noise Synthesis (구조-음향 상반성 원리를 이용한 공기기인 소음원의 강도 추정 및 소음 합성)

  • Kim, Yoon-Jae;Byun, Jae-Hwan;Kang, Yeon-June;Hong, Jin-Chul;Kwon, O-Jun;Kang, Koo-Tae
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.1
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    • pp.42-49
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    • 2009
  • In this paper, an alternative method was introduced to conduct a transfer path analysis for airborne noise. The method used the transfer function matrix composed of acoustic transfer functions that are referenced by the input voltage of a calibration source. A calibration factor which is converting a virtual voltage to source strength was deduced by vibro-acoustical reciprocity theorem. The calibration factor is then multiplied to the virtual input voltage to estimate the operational source strength. Three loudspeakers were used to noise sources of acrylic half car model. The method was applied to airborne noise transfer path analysis of the half car. The estimated source strength by transfer path analysis was compared the deduced source strength by vibro-acoustical reciprocity to verify the method.