def window_hann(N):
from numpy import hanning<EOL>return hanning(N)<EOL>
r"""Hann window (or Hanning). (wrapping of numpy.bartlett)

    :param int N: window length

    The Hanning window is also known as the Cosine Bell. Usually, it is called
    Hann window, to avoid confusion with the Hamming window.

    .. math:: w(n) =  0.5\left(1- \cos\left(\frac{2\pi n}{N-1}\right)\right)
               \qquad 0 \leq n \leq M-1

    .. plot::
        :width: 80%
        :include-source:

        from spectrum import window_visu
        window_visu(64, 'hanning')

    .. seealso:: numpy.hanning, :func:`create_window`, :class:`Window`.