Speech is a complicated signal produced as results of several transformations occurring at several different levels: semantic, linguistic, articulatory and acoustic. Differences in these transformations appear as differences in the acoustic properties of the speech signal. In speaker identification, all these differences can be used to discriminate between speakers. In older techniques, speaker identification was carried out through speaker's spectrogram, but it was difficult to analysis these spectrum. In this book, the detail of every step in automatic speaker identification process is given with explanations of ideas, which led to these techniques. Starting from the basic definitions used in Digital Signal Processing and moving to the feature extraction steps and speaker modelling techniques is done. The different techniques and results of speaker identification are discussed. This book, therefore, provides techniques for automatic speaker identification and useful to professionals working in Digital Signal Processing.