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Modal Analysis

  • Thomas D. Rossing

Abstract

Modal analysis is widely used to describe the dynamic properties of a structure in terms of the modal parameters: natural frequency, damping factor, modal mass and mode shape. The analysis may be done either experimentally or mathematically. In mathematical modal analysis, one attempts to uncouple the structural equations of motion so that each uncoupled equation can be solved separately. When exact solutions are not possible, numerical approximations such as finite-element and boundary-element methods are used.

In experimental modal testing, a measured force at one or more points excites the structure and the response is measured at one or more points to construct frequency response functions. The modal parameters can be determined from these functions by curve fitting with a computer. Various curve-fitting methods are used. Several convenient ways have developed for representing these modes graphically, either statically or dynamically. By substituting microphones or intensity probes for the accelerometers, modal analysis methods can be used to explore sound fields. In this chapter we mention some theoretical methods but we emphasize experimental modal testing applied to structural vibrations and also to acoustic fields.

Keywords

Mode Shape Frequency Response Function Sound Field Modal Assurance Criterion Fast Fourier Transform Analyzer 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Abbreviations

3-D

three-dimensional

ADC

analog-to-digital converter

BEM

boundary-element method

DC

direct current

DOF

degree of freedom

DSI

digital speckle interferometry

ESPI

electronic speckle-pattern interferometry

FEA

finite-element analysis

FEM

finite-element method

FFT

fast Fourier transform

FRF

frequency response function

IMAC

International Modal Analysis Conference

IRF

impulse response function

MAC

modal assurance criterion

MDOF

multiple degree of freedom

MEMS

microelectromechanical system

MIMO

multiple-input multiple-output

ODS

operating deflexion shape

SDOF

single-degree-of-freedom

TV

television

UMM

unit modal mass

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Copyright information

© Springer-Verlag 2014

Authors and Affiliations

  1. 1.Center for Computer Research in Music and Acoustics (CCRMA) Department of MusicStanford UniversityStanfordUSA

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