Relating pain intensity of newborns to onset of nonlinear phenomena in   cry recordings
  The cries of several full term newborns, recorded during blood sampling, were analyzed. Spectrograms showed the appearance of irregular patterns related to the pain assessed using the method of the DAN scale. In particular, the appearance of Noise concentration Patterns (NP) in spectrograms was related to the increase of the pain suffered by the newborns. In this scenario, pain constitutes a bifurcation parameter for the vocal folds dynamic, inducing a Ruelle-Takens-Newhouse chaotic transition. 
A. Facchini, C.V. Bellieni, N. Marchettini, F.M. Pulselli, E. B.P.   Tiezzi