METHOD AND DEVICE FOR DETERMINING A ROOM ACOUSTIC IMPULSE RESPONSE IN THE TIME DOMAIN

2013 ◽  
Vol 133 (3) ◽  
pp. 1850
Author(s):  
Wolfgang Ahnert
Keyword(s):  
Impulse Response ◽  
Time Domain ◽  
The Time Domain

scholarly journals Convolution-based time-domain simulation for fluidelastic instability in tube arrays

2021 ◽  
Author(s):  
Mingjie Zhang ◽  
Ole Øiseth
Keyword(s):  
Impulse Response ◽  
Response Function ◽  
Time Domain ◽  
Impulse Response Function ◽  
Time Domain Simulation ◽  
Unit Step ◽  
Tube Arrays ◽  
Unit Impulse ◽  
The Time Domain ◽  
Unit Impulse Response

AbstractA convolution-based numerical algorithm is presented for the time-domain analysis of fluidelastic instability in tube arrays, emphasizing in detail some key numerical issues involved in the time-domain simulation. The unit-step and unit-impulse response functions, as two elementary building blocks for the time-domain analysis, are interpreted systematically. An amplitude-dependent unit-step or unit-impulse response function is introduced to capture the main features of the nonlinear fluidelastic (FE) forces. Connections of these elementary functions with conventional frequency-domain unsteady FE force coefficients are discussed to facilitate the identification of model parameters. Due to the lack of a reliable method to directly identify the unit-step or unit-impulse response function, the response function is indirectly identified based on the unsteady FE force coefficients. However, the transient feature captured by the indirectly identified response function may not be consistent with the physical fluid-memory effects. A recursive function is derived for FE force simulation to reduce the computational cost of the convolution operation. Numerical examples of two tube arrays, containing both a single flexible tube and multiple flexible tubes, are provided to validate the fidelity of the time-domain simulation. It is proven that the present time-domain simulation can achieve the same level of accuracy as the frequency-domain simulation based on the unsteady FE force coefficients. The convolution-based time-domain simulation can be used to more accurately evaluate the integrity of tube arrays by considering various nonlinear effects and non-uniform flow conditions. However, the indirectly identified unit-step or unit-impulse response function may fail to capture the underlying discontinuity in the stability curve due to the prespecified expression for fluid-memory effects.

Transient axisymmetric motion of a floating cylinder

1985 ◽  
Vol 157 ◽  
pp. 17-33 ◽  
Author(s):  
J. N. Newman
Keyword(s):  
Free Surface ◽  
Frequency Domain ◽  
Impulse Response ◽  
Response Function ◽  
Time Domain ◽  
Impulse Response Function ◽  
Surface Effects ◽  
Added Mass ◽  
The Body ◽  
The Time Domain

A linear theory is developed in the time domain for vertical motions of an axisymmetric cylinder floating in the free surface. The velocity potential is obtained numerically from a discretized boundary-integral-equation on the body surface, using a Galerkin method. The solution proceeds in time steps, but the coefficient matrix is identical at each step and can be inverted at the outset.Free-surface effects are absent in the limits of zero and infinite time. The added mass is determined in both cases for a broad range of cylinder depths. For a semi-infinite cylinder the added mass is obtained by extrapolation.An impulse-response function is used to describe the free-surface effects in the time domain. An oscillatory error observed for small cylinder depths is related to the irregular frequencies of the solution in the frequency domain. Fourier transforms of the impulse-response function are compared with direct computations of the damping and added-mass coefficients in the frequency domain. The impulse-response function is also used to compute the free motion of an unrestrained cylinder, following an initial displacement or acceleration.

Noncausality of the discrete‐time magnetotelluric impulse response

Geophysics ◽  
1992 ◽  
Vol 57 (10) ◽  
pp. 1354-1358 ◽  
Author(s):  
Gary D. Egbert
Keyword(s):  
Magnetic Fields ◽  
Frequency Domain ◽  
Impulse Response ◽  
Discrete Time ◽  
Time Domain ◽  
Linear Relation ◽  
External Source ◽  
The Time Domain ◽  
Treat All ◽  
Time Invariant

Under the assumption that the external source magnetic fields are uniform, the electric (E) and magnetic (H) fields observed at the surface of the conducting earth satisfy a time‐invariant linear relation, which may be expressed as multiplication in the frequency domain, [Formula: see text], Eq. (1), or as convolution in the time domain, [Formula: see text], Eq. (2). Here the tilde denotes quantities in the frequency domain; e.g., [Formula: see text] is the frequency‐domain magnetotelluric (MT) impedance, and Z the corresponding time‐domain impulse response. For simplicity in the following discussion, I treat all quantities as scalars, although the operations in equations (1) and (2) generally involve vectors and tensors.

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