In the Netherlands alone, there were approximately 25 million telephone connections in the year 2007. There are 16 million Dutchmen, so that means that every Dutchmen has at least 1,5 telephones available. If we assume half of these telephones are used on a daily basis then we can say that in the Netherlands alone 12,5 million phone calls are being conducted. This in turn means that there is a lot of information is transferred by the means of a telephone. For national security agencies this is a huge problem. To find a (potential) dangerous call amongst a lot of other calls, security agencies need a set of tools to automatically analyze this big heap of data. This book on language recognition is aimed at analyzing audio files so the language that is used by subjects in the audio file can be identified.