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'''Modal testing''' is the form of [[vibration|vibration testing ]] of an object whereby the natural (modal) frequencies, modal masses, modal damping ratios and mode shapes of the object under test are determined.▼
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▲'''Modal testing''' is the form of [[vibration|vibration testing ]] of an object whereby the natural (modal) frequencies,<ref>{{Cite web |date=2021-08-19 |title=Vibration Tests for Moon Rocket Help Ensure Safe Travels on Road to Space - NASA |url=https://www.nasa.gov/missions/artemis/orion/vibration-tests-for-moon-rocket-help-ensure-safe-travels-on-road-to-space/ |access-date=2025-06-30 |language=en-US}}</ref> modal masses, modal damping ratios and mode shapes of the object under test are determined.
A modal test consists of an acquisition phase and an analysis phase. The complete process is often referred to as a [[Modal Analysis]]<ref>{{Cite journal |last=Shen |first=Longjiang |last2=He |first2=Shizhong |date=2024-09-14 |title=Modal analysis and frequency matching study of subway bogie frame under ambient excitation |url=https://www.nature.com/articles/s41598-024-72146-z |journal=Scientific Reports |language=en |volume=14 |issue=1 |pages=21484 |doi=10.1038/s41598-024-72146-z |issn=2045-2322}}</ref> or Experimental Modal Analysis.
There are several ways to do modal testing but impact hammer testing and shaker (vibration tester) testing are commonplace. In both cases [[energy]] is supplied to the system with a known frequency content. Where structural resonances occur there will be an [[Amplifier|amplification]] of the response, clearly seen in the response spectra. Using the response spectra and force spectra, a [[transfer function]] can be obtained. The transfer function (or [[frequency response function]] (FRF)) is often [[curve fitting|curve fitted]] to estimate the modal parameters; however, there are many methods of modal [[Estimation theory|parameter estimation]] and it is the topic of much research.[[File:Vibration testing.svg|thumb|Key components for performing experimental modal analysis.|center|636x636px]]
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