What determines peaks in FFT?

Peaks are determined by energy in a given frequency range which can be more or less visible depending on the dimension of frequency bins.

1. What do the peaks mean in FFT?
2. How do you get to peaks in FFT?
3. Why does FFT have two peaks?
4. How do you find the spectral peak?

What do the peaks mean in FFT?

The peaks are the frequencies at which the vibration amplitude is maximal. Here, they appear to be at about 900 Hz, and about 1200-1300 Hz.

How do you get to peaks in FFT?

Look for points where the value for the difference function goes from positive to negative. Those are your peak points. To find the most prominent peaks, compute the second order difference function at the points obtained from the first order difference and select the ones which are of highest magnitude.

Why does FFT have two peaks?

It's not two peaks, it's one peak, but an FFT is always mirror-symmetric. Only the first half is actually useful. Think of it this way: an FFT can't pick up signal data at more than half the sampling rate. When you try you get essentially garbage data that just so happens to be a mirrored refection of the "real" FFT.

How do you find the spectral peak?

For a particular spectral peak, the dichroic ratio R is defined by the relationshipR = A⊥/A∥where A⊥ and A∥ are the absorption of the LB films when the light is polarized perpendicular or parallel to the dipping direction, respectively.