  We consider sequences of needlet random fields defined as weighted averaged
forms of spherical Gaussian eigenfunctions. Our main result is a Central Limit
Theorem in the high energy setting, for the boundary lengths of their excursion
sets. This result is based on Stein-Malliavin techniques and Wiener chaos
expansion for nonlinear functionals of random fields. To this end, a careful
analysis of the variances of each chaotic component of the boundary length is
carried out, showing that they are asymptotically constant, after
normalisation, for all terms of the expansion and no leading component arises.
