Thresholding estimators in an orthonormal wavelet basis are well established tools for Gaussian noise removal. However, the threshold choice ̧ = 3⁄4 p (2logN) suggested by Donoho and Johnstone, implies the knowledge of the variance 3⁄4 of the noise. In this talk we consider the denoising problem as a variational problem, whose solution can be formulated in terms of wavelet shrinkage, and we prop...