Adaptive filtering techniques for gravitational wave interferometric data:Removing long-term sinusoidal disturbances and oscillatory transients - art. no. 042004

It is known by the experience gained from the gravitational wave detector p rototypes that the interferometric output signal will be corrupted by a sig nificant amount of non-Gaussian noise, a large part of it bring essentially composed of long-term sinusoids with a slowly varying envelope (such as vi olin resonances in the suspensions, or main power harmonics) and short-term ringdown noise (which may emanate from servo control systems, electronics in a nonlinear state, etc.). Since non-Gaussian noise components make the d etection and estimation of the gravitational wave signature more difficult, a denoising algorithm based on adaptive filtering techniques (LMS methods) is proposed to separate and extract them from the stationary and Gaussian background noise. The strength of the method is that it does not require an y precise model on the observed data: the signals are distinguished on the basis of their autocorrelation time. We believe that the robustness and sim plicity of this method make it useful for data preparation and for the unde rstanding of the first interferometric data. We present the detailed struct ure of the algorithm and its application to both simulated data and real da ta from the LIGO 40 m prototype.