Applies Kaiser window to Src. Beta parameter controls the width the of the mainlobe and spectral leakage. Beta allows you to find a compromise between the frequency resolution and attenuation of the spectral leakage. Window functions are applied to the signal prior to conversion to frequency domain with the FFT algorithm, to reduce the spectral leakage. Their side-effect is a lower frequency resolution. 

If a specified sidelobe attenuation is required for spectrum analysis, the appropriate beta can be found with the KaiserBetaWindow routine. 

If a specified sidelobe attenuation is required for a FIR filter, the appropriate beta can be found with the KaiserBetaFir routine. 

The equation for Kaiser window and application to the FIR filter design can be found in [1] p. 453. 

References:  

[1] Discrete-time signal processing, Oppenheim and Schafer, Prentice-Hall, 1989.

Hanning, FirImpulse, SignalWindow

Kaiser Method