Change the default FFT window

[towsey]

Currently the default FFT window is the Hamming window.
This default is set in the class SpectrogramSettings at line 29:
public string WindowFunction { get; set; } = WindowFunctions.HAMMING.ToString();

Recent experience indicates that this window is not as good as the Hanning window.
The default should be change d to Hanning. However, because the FFT window is used early in the signal processing sequence, this change may cause multiple tests to fail.

[atruskie]

Can you show the effect of the different window function please? Add a couple of pictures into the response.
I believe you said resampling in combination with hamming causes side band effects?

We'll go ahead with this change but after .Net Core branch is merged in

[towsey]

Here is an example of the Hamming window with detection of Plains Wanderer calls.

Here is an example of the Hann

ing window with detection of Plains Wanderer calls.

The Hanning window offers a cleaner spectrogram and therefore better detection of Plains Wanderer whistles.

[towsey]

I have run both Hanning and Hamming windows on a frequently used test recording from Hendra Brisbane and can see no difference between the resulting spectrograms. So it would appear that the major difference arises only for recordings that have been resampled either up or down. Due to the significant difference in the resampled situation, I therefore propose that we switch to HANNING window as default. This may or may not result in a number of breaking unit tests depending on how many use a resampled signal.