—The X-GLOS (EXtraction of GLOttal Sources) method for separating the glottal and the supraglottal sources in speech signals is presented in this article. Unlike other periodic/aperiodic decomposition methods that use stationary models of the signal within frames, X-GLOS considers locally varying instantaneous fundamental frequency. Applications on numerically synthesized fricative signals prove the locally non-stationary model to be more robust to moderate and high jitter values than stationary models. A peak picking selection also allows X-GLOS to be less sensitive to high colored noise levels. The gain of performance, in comparison with the reference existing method, is about a couple of dozens of dB in high noise-to-harmonics ratios. X-GLOS can then be specifically used to study the behavior of the voicing and frication noise sources independently, even at vowel-consonants behavior where the voiced source is less powerful that the frication noise in the recorded mixture speech signal.