In speech signal processing, the source filter model is a mathematical model that represents the [[speech signal]] by a combination of a sound source with a linear acoustic filter. The sound source for voiced sounds needs to model the [[glottal airflow velocity]]. For unvoiced sounds, the source needs to model the noise produced by the turbulent airflow at a vocal constriction. The acoustic filter aims to model the way the vocal tract shapes the spectral envelope of speech sounds. It is often modeled by a [[discrete-time LTI system]]. A simplified model can be represented as: ![[source-filter-model.png]] [[Huang 2001]] In this model, the source can be an impulse train to simulate the [[voiced phonation]] or white noise for the [[unvoiced phonation]]. More complex models use a weighted sum of periodic and non-periodic signals for the source signal.