Can I take piecewise FFT of a larger input sample?

1. How many data points needed for FFT?
2. How do you find the length of a FFT?
3. What is bin spacing?

How many data points needed for FFT?

Typical benchtop instruments use FFTs of 1,024 and 2,048 points.

How do you find the length of a FFT?

FR = Fmax/N(Bins)

For a 44100 sampling rate, we have a 22050 Hz band. With a 1024 FFT size, we divide this band into 512 bins. FR = 22050/1024 ≃ 21,53 Hz. Basically, the FFT size can be defined independently from the window size.

What is bin spacing?

The bandwidth of the FFT is divided into bins, the number of which is 1/2 the FFT length. The bin width (also called line spacing) defines the frequency resolution of the FFT. The FFT provides amplitude and phase values for each bin. The bin width is stated in hertz.