  The energy spectral density $E(k)$, where $k$ is the spatial wave number, is
a well-known diagnostic of homogeneous turbulence and magnetohydrodynamic
turbulence. However in most of the curves plotted by different authors, some
systematic kinks can be observed at $k=9$, $k=15$ and $k=19$. We claim that
these kinks have no physical meaning, and are in fact the signature of the
method which is used to estimate $E(k)$ from a 3D spatial grid. In this paper
we give another method, in order to get rid of the spurious kinks and to
estimate $E(k)$ much more accurately.
