Abstract : The method of surrogate data, classically used for nonlinearity tests, amounts to the use of some constrained noise providing reference for statistical test. It is revisited here as a method for stationarization and this feature is put forward in the context of nonstationarity testing. The stationarization property of surrogates is first explored in a time-frequency perspective and used for devising a test of stationarity relative to an observation time. Then, more general forms of surrogates are developed, directly in time-frequency or mixed domains of representation (ambiguity and time-lag domains included) and it is shown how they allow for other tests of nonstationary features: detection of the existence of a transient in some noise; assessment of nonstationary cross-correlations.
