  We study a new procedure to measure the sound horizon scale via Baryonic
Acoustic Oscillations (BAO). Instead of fitting the measured power spectrum
(PS) to a theoretical model containing the cosmological informations and all
the nonlinear effects, we define a procedure to project out (or to "extract")
the oscillating component from a given nonlinear PS. We show that the BAO scale
extracted in this way is extremely robust and, moreover, can be reproduced by
simple theoretical models at any redshift. By using N-body simulations, we
discuss the effect of the nonlinear evolution of the matter field, of redshift
space distortions and of scale-dependent halo bias, showing that all these
effects can be reproduced with sub-percent accuracy. We give a one-parameter
theoretical model based on a simple (IR) modification of 1-loop perturbation
theory, which reproduces the BAO scale from measurements of halo clustering in
redshift space at better than $0.1\%$ level and does not need any external UV
input, such as coefficients measured from N-body simulations.

Cosmology and Nongalactic Astrophysics;High Energy Physics - Phenomenology;High Energy Physics - Theory