I'm experimenting with a 30 Hz sine wave and I want to extract the frequencies of this, and have implemented the algorithm to do so. This gives a correct reading, well, gives 29 Hz.
I'm now wanting to compute the algorithm for an STFT. So, for this, I use
NFFT = 256 with an overlap of
128, using the Hanning Window function.
This gives me a series of bins which I can then calculate the frequency formula on. However, when I graph this, the results do not seem right, for some reason:
I mean, it might just be me in thinking that the results do not look right, however, if they are, why would the results be this? I just don't get it.
For example, I was expecting when the energy is low, the result would be low and thus when the energy was high, the result would be high. Let me give you another example on a more structured sound file.
Sample rate = 12000 NFFT = 256 Overlap = 128
And the STFT output for this is below:
Am I doing something wrong here, or, do these results look ok?