• 한국소음진동공학회논문집
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• 제24권6호
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• pp.483-492
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• 2014

Uncomfortable feelings of occupants by indoor floor impact noise in a residential building are not accurately represented by the floor impact noise from a standard impact source. It is due to the characteristics of standard impact sources, which are different from the impact forces produced by occupants. It varies significantly by impact source, and it is not easy to be replicated for testing. As a result, the indoor floor impact noise under different acoustic conditions cannot be directly compared. Using frequency response function(FRF), which represents the input-output relationships of a dynamic system, it is possible to examine the characteristics of the system. Especially, FRF can predict the response of a linear dynamic system subjected to various excitation. To determine the relationship between impact force and the corresponding response of dynamic system in residential building, the acceleration response of a concrete slab and the floor impact noise in the living room, produced by bang-machine and rubber-ball excitation, were measured. The test results are compared to the estimates based on FRF and impact force spectrum.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.71-77
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• 2002

The spectrum of impulse response signal which is obtained from an impulse hammer testing is used for frequency response function, nevertheless it has serious faults when the record length for the signal processing is not very long. The faults cannot be avoided with the conventional signal analyzer that is processing all the signals as if they are always periodic. The signals generated by the impact hammer are undoubtedly non-periodic because of the damping, and are acquired for limited recording time due to the memory as well as the computation performance of the signal analyzer. This paper will make clear the relation between the faults and the length of recording time, and propose the way for solving the faults.

• 한국항공우주학회지
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• 제34권8호
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• pp.41-46
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• 2006

충격응답함수와 조정법(regularization methods)을 이용하여 항공기 날개의 충격하중 복원 가능성을 검토하였다. 충격하중에 대한 구조의 응답을 내타낼 수 있는 충격응답함수를 날개 유한요소모델의 강성과 질량 자료로 유도하였다. 일반적으로 부적합(ill-posed) 특성을 지닌 충격응답함수의 역행렬은 반복 Tikhonov 조종법(Iterative Tikhonov Regularization Method)과 일반화 특이치 분해법(Generalized Singular Value Decomposition Method)을 사용하여 구하였다. 수치적 입증을 위하여 전투기급 주익을 사용하였다. 해당 주익의 유한요소해석을 통하여 임의의 충격하중에 대한 변위와 변형률을 계산하였으며, 이를 충격응답함수로 계산한 결과와 비교하였다. 또한, 유한요소해석에서 계산된 변형률을 사용하여 충격하중을 복원하였다. 수치적 입증 결과 항공기 구조의 충격하중 모니터링이 본 방법으로 가능할 수 있음을 보여주었다.

• 한국소음진동공학회논문집
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• 제12권9호
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• pp.702-708
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function(FRF). However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the errors. This paper makes clear the relation between the errors of FRF and the length of recording time. A new method is suggested to reduce the errors of FRF in this paper. Several numerical examples for 1-dof model are carried out to show the property of the errors and the validity of the proposed method.

• 소음진동
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• 제9권4호
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• pp.778-784
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• 1999

A method for obtaining the motion of an impact system whose primary and secondary system are composed of lumped masses, springs and dampers, and all the contacts are made through spring and damping elements is presented. The frequency response functions derived from the equations of motion and the impulse response functions obtained from the inverse Fourier transform of the derived frequency response functions are used for the calculation of the system responses. The procedure developed for the calculation of displacements and force time-histories was based on the convolution integrals of impulse response functions and forces applied to the systems. Time histories of displacements and contact forces are obtained for the case where a random excitation is applied to a point in the system. Impact statistics such as contact forces and the time between impacts calculated from those time histories is presented.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.623-629
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function(FRF) of the structure. However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the finite record length error and the leakage error. In this paper, the errors in the frequency response function of multi degree of freedom system are formulated theoretically. And the method to remove these errors is also suggested. This method is based on the optimization technique. A numerical example of 3-dof model shows the validity of the proposed method.

• 한국소음진동공학회논문집
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• 제12권10호
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• pp.792-798
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function (FRF) of the structure. However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the finite record length error and the leakage error. In this paper, the errors in the frequency response function of multi degree of freedom system are formulated theoretically. And the method to remove these errors is also suggested. This method is based on the optimization technique. A numerical example of 3-dof model shows the validity of the proposed method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.363.2-363
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function(FRF) of the structure. However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. (omitted)

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.517-522
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• 2002

The frequency response function(FRF) of each substructure is used for the transfer function synthesis method(TFS). The dynamic characteristics of the full system are obtained by synthesizing FRFs of each substructure. The validation of TFS depends on accuracy for FRF of each substructure. Impact hammer testing is widely used to obtain the modal characteristics of structures. However, the FRF obtained from impact hammer testing contains several errors, such as finite record length error and leakage error of which characteristic depends on data acquisition time which we call record length. In this paper, a method to remove these errors is proposed so as to enhance results of TFS. Numerical examples show that the FRF of full structure can be predicted exactly by the method proposed in this paper.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.227-228
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• 2023

A floating floor generally consists of mortar bed separated from the structural RC slab by a continuous resilient layer. It is known that the floating floors are a type of vibration-isolation system to improve the impact sound insulation performance. However, some researchers have demonstrated that the amplification of vibration response at a specific range of frequencies results in an increase in the impact sound level. This study carried out the forced vibration tests to obtain the frequency response function (FRF) of a floating floor compared with a bare RC slab. Test results shows that the additional peak occur in vibrational spectrum of the floating floor except natural vibration modes of the bare RC slab. This is because the relatively flexible resilient material and mass of the mortar bed offer an additional degree of freedom in the structural system. Therefore, it could be efficient for reduction of floor impact vibration and noise to control the additional mode frequency and response of floating floors.