Denoising Long-Wave Records
Derek G. Goring · 2004
σ λ ˆ log 2 n e u = (1) where σ is an estimate of the population’s standard deviation (in practice, σ is calculated as the mean of the absolute difference, or MAD, which is more robust than the standard deviation of the sample). The universal threshold method assumes that all wavelet coefficients less than u λ are noise, and these are eliminated. An inherent assumption in this method is that the noise is Gaussiandistributed. We have no evidence that this is true for long-wave records.