Analytical representation of hydrophone complex frequency response

2021 ◽  
pp. 16-20
Author(s):  
Alexander E. Isaev
Keyword(s):  
Frequency Response ◽  
Complex Variable ◽  
Active Element ◽  
Analytical Representation ◽  
Complex Frequency ◽  
Minimum Phase ◽  
Experimental Frequency ◽  
Resonance Properties ◽  
Fractional Rational Function ◽  
Sound Diffraction

The problem of analytical representation of hydrophone complex frequency response based on a model consisting of an advance line and a minimum-phase part, which describing the effect of sound diffraction and resonance properties of an active element, is considered. Algorithms are proposed for approximating the hydrophone complex frequency response by a fractional-rational function of the complex variable according to the data of the hydrophone amplitude-frequency and/or phasefrequency responses. Examples of the application of these algorithms for processing experimental frequency characteristics of hydrophones are given.

Determination of the hydrophone phase-frequency response by its amplitude-frequency response

2021 ◽  
pp. 48-53
Author(s):  
Alexander E. Isaev ◽  
Bulat I. Khatamtaev
Keyword(s):  
Frequency Response ◽  
Active Element ◽  
Primary Standard ◽  
Acoustic Measurements ◽  
Amplitude Frequency Response ◽  
Resonance Properties ◽  
The Hilbert Transform ◽  
Sound Diffraction ◽  
Inverse Operation

One of the tasks of the COOMET 786/RU/19 pilot comparisons is to check the correctness of the hydrophone model proposed in VNIIFTRI, consisting of an advance line and a minimum-phase part, including the effect of sound diffraction and resonance properties of the active element. This model makes it possible to use the Hilbert transform to obtain the phase-frequency response from the amplitude-frequency response as well as for inverse operation. The results of measuring experiments performed using facilities of the State Primary Standard GET 55-2017 are presented. For many practical tasks, it is not necessary to obtain the phase-frequency response for an acoustic center of the receiver. It is enough to determine the shape of the phase-frequency response using much less laborious methods. The question of which of the characteristics is expedient to determine during calibration - for an acoustic center, or for a point on the surface of an active element, deserves a discussion among specialists performing acoustic measurements.

Experimental Study for Extraction of Normal Modes

1995 ◽  
Author(s):  
S. Y. Chen ◽  
M. S. Ju ◽  
Y. G. Tsuei
Keyword(s):  
Frequency Response ◽  
Normal Mode ◽  
Normal Modes ◽  
Measurement Data ◽  
Mode Shapes ◽  
Complex Frequency ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Incomplete System ◽  
Coupled Structures

Abstract A frequency-domain technique to extract the normal mode from the measurement data for highly coupled structures is developed. The relation between the complex frequency response functions and the normal frequency response functions is derived. An algorithm is developed to calculate the normal modes from the complex frequency response functions. In this algorithm, only the magnitude and phase data at the undamped natural frequencies are utilized to extract the normal mode shapes. In addition, the developed technique is independent of the damping types. It is only dependent on the model of analysis. Two experimental examples are employed to illustrate the applicability of the technique. The effects due to different measurement locations are addressed. The results indicate that this technique can successfully extract the normal modes from the noisy frequency response functions of a highly coupled incomplete system.

scholarly journals Coupling of structures using frequency response functions

2018 ◽  
Vol 211 ◽  
pp. 06005
Author(s):  
Tiago Silva ◽  
João Pereira
Keyword(s):  
Frequency Response ◽  
Numerical Models ◽  
Complete Response ◽  
Modal Identification ◽  
Response Model ◽  
Response Functions ◽  
Experimental Frequency ◽  
Frequency Response Functions ◽  
Structural Modifications ◽  
Combined Use

In the field of structural dynamics is common to predict the behaviour of a structure regarding structural modifications. In this context, the frequency based substructuring method is well-known to perform structural modifications based on the coupling of structures. This process gives the possibility to perform the study of a structure at the level of its components and then assess the response of the coupled system. In practice, it is impossible to attain an experimental complete response model, although one can simulate all the responses of a structure using numerical models. Hence, the substructuring process can be enhanced by the combined use of experimental and numerical responses, as it was demonstrated using numerically obtained frequency response functions. This work presents the enhancement of the frequency based substructuring method using a method to expand experimental frequency response functions over the entire set of degrees of freedom in a finite element model. This expansion process, known as modified Kidder’s method, considers that if one can only measure translations due to exciting force, it is possible to obtain the complete response model, including the rotational frequency response functions due to exciting moments. The combined use of the frequency based substructuring and the modified Kidder’s methods has several advantages, as it avoids modal identification or residual compensation. To evaluate the performance of the proposed procedure a numerical example of a beam structure is presented, and its results are discussed.

Model-updating with experimental frequency response function considering general damping

2017 ◽  
Vol 21 (1) ◽  
pp. 82-92 ◽  
Author(s):  
Yu Hong ◽  
Qianhui Pu ◽  
Yang Wang ◽  
Liangjun Chen ◽  
Hongye Gou ◽  
...  
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Model Updating ◽  
Experimental Frequency

Transfer Functions of One-Dimensional Distributed Parameter Systems by Wave Approach

2006 ◽  
Vol 129 (2) ◽  
pp. 193-201 ◽  
Author(s):  
B. Kang
Keyword(s):  
Transfer Function ◽  
Frequency Response ◽  
Wave Reflection ◽  
Transfer Functions ◽  
Distributed Parameter Systems ◽  
Distributed Parameter ◽  
Complex Frequency ◽  
Reflection And Transmission ◽  
One Dimensional ◽  
Analysis Technique

An alternative analysis technique, which does not require eigensolutions as a priori, for the dynamic response solutions, in terms of the transfer function, of one-dimensional distributed parameter systems with arbitrary supporting conditions, is presented. The technique is based on the fact that the dynamic displacement of any point in a waveguide can be determined by superimposing the amplitudes of the wave components traveling along the waveguide, where the wave numbers of the constituent waves are defined in the Laplace domain instead of the frequency domain. The spatial amplitude variations of individual waves are represented by the field transfer matrix and the distortions of the wave amplitudes at point discontinuities due to constraints or boundaries are described by the wave reflection and transmission matrices. Combining these matrices in a progressive manner along the waveguide using the concepts of generalized wave reflection and transmission matrices leads to the exact transfer function of a complex distributed parameter system subjected to an externally applied force. The transient response solution can be obtained through the Laplace inversion using the fixed Talbot method. The exact frequency response solution, which includes infinite normal modes of the system, can be obtained in terms of the complex frequency response function from the system’s transfer function. This wave-based analysis technique is applicable to any one-dimensional viscoelastic structure (strings, axial rods, torsional bar, and beams), in particular systems with multiple point discontinuities such as viscoelastic supports, attached mass, and geometric/material property changes. In this paper, the proposed approach is applied to the flexural vibration analysis of a classical Euler–Bernoulli beam with multiple spans to demonstrate its systematic and recursive formulation technique.

Coupling Sound Absorbing Materials With an Air Cavity Using Frequency Dependent Bulk Material Properties

2016 ◽  
Author(s):  
Shung H. Sung ◽  
Donald J. Nefske
Keyword(s):  
Finite Element ◽  
Frequency Response ◽  
Material Properties ◽  
Complex Frequency ◽  
Air Cavity ◽  
Frequency Dependent ◽  
Absorbing Materials ◽  
Mode Method ◽  
Modal Solution ◽  
Solution Methodology

This paper presents the acoustic finite element method and the modal solution method for coupling sound absorbing materials with an air cavity to predict the sound pressure frequency response. The sound absorbing materials are represented with complex, frequency-dependent, effective mass-density and bulk-modulus properties obtained from the acoustic impedance of material samples. To couple the sound absorber cavity and air cavity, the boundary conditions at the interface between the cavities requires equality of pressure and equality of acoustic volume flow. Two modal solution methods are developed to compute the frequency response of the coupled system with frequency dependent material properties: the component mode method and the coupled mode method. The finite element and modal solution methodology is developed in a form readily adaptable for implementation in commercially available codes. The accuracy of the modal solution methodology is assessed for modeling a one-dimensional air tube terminated with absorbent material and the seats in an automobile passenger compartment.

True and apparent spectra of buried polarizable targets

Geophysics ◽  
1984 ◽  
Vol 49 (2) ◽  
pp. 171-176 ◽  
Author(s):  
D. Guptasarma
Keyword(s):  
Numerical Modeling ◽  
Phase Shift ◽  
Host Rock ◽  
Field Measurements ◽  
Phase Spectrum ◽  
Complex Frequency ◽  
Minimum Phase ◽  
Dilution Factor ◽  
Shift Type ◽  
Phase Spectra

If the chargeability of a buried target is not infinitesimal, the popularly used low chargeability approximation formulated by Seigel (1959) can produce large errors in the computation of apparent polarizability spectra. A more accurate alternative approximation, based on a complex, frequency dependent “dilution factor” is presented. It turns out that for dispersions of the minimum phase shift type this approximation can be somewhat simplified and that for targets with such a dispersion, buried in a nondispersive host rock, the apparent log‐phase spectrum is only slightly different from a vertically shifted version of the true phase spectrum of the target. These results should be useful for the computation of apparent polarizabilities in numerical modeling for IP, and in attempts for mineral discrimination through field measurements of phase spectra.

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