The equivalent noise bandwidth of a window
is the width of a rectangle whose area contains the same total power
as the window. The height of the rectangle is the peak squared magnitude
of the window’s Fourier transform.

Assuming a sampling interval of 1, the total energy for the
window, *w*(*n*), can be expressed
in the frequency or time-domain as

The peak magnitude of the window’s spectrum occurs at *f* = 0. This is given
by

To find the width of the equivalent rectangular bandwidth, divide
the area by the height.

See Equivalent Rectangular Noise Bandwidth for an example that
plots the equivalent rectangular bandwidth over the magnitude spectrum
of a von Hann window.