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Explore the influence of amplitude, frequency, and phase on waveforms and spectra using Fourier analysis. Study the impact of adjusting amplitudes and phases on harmonic components. Learn how to transform waveforms into spectra and vice versa. Discover the principles of Fourier analysis explained through interactive applets.
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Waveform and Spectrum A visual Fourier Analysis
Wave form Sin(2 f t) + Sin(2 2f t) + Sin(2 3f t) +… How about the amplitude? A1 Sin(2 f t) + A2Sin(2 2f t) +A3Sin(2 3f t) +… Does every harmonic contribute the same? How does the wave form change if we vary the Amplitude for each harmonic?
From wave form to spectrum… A1 Sin(2 f t) + A2Sin(2 2f t) +A3Sin(2 3f t) +… Amplitude frequency f 2f 3f 4f 5f
Amplitude Relative Amplitude Time frequency …back to wave form 50 harmonics 5 harmonics
Influence of Phase (/2 for each) 3f, shifted by 2/3λ f 2f 2f, shifted by /4
Influence of Phase (/2 for each) 10 harmonics 3 harmonics 50 harmonics
Fourier Analysis • Joseph Fourier (1768-1830) Any periodic vibration can be build from a series of simple vibrations whose frequencies are harmonics of a fundamental frequency, by choosing the proper amplitude and phase.
Applets for Fourier transformation • http://falstad.com/fourier/ • http://www.phy.ntnu.edu.tw/java/sound/sound.html • http://www.colorado.edu/physics/2000/applets/fourier.html