The issue of studying the linguistic variation, caused by the stratification of society into different strata and groups, has not been solved so far, remaining one of the key issues in modern linguistics. This article deals with the concept “nonstandard dialect” in the framework of sociolinguistic research into the German-speaking tradition, which belongs to the field of studies of linguistic variability of the German language native speakers. Nonstandard dialects may differ from other forms of language existence, as well as from the literary language at all linguistic levels: phonological, grammatical, syntactical, lexical and idiomatic. We examine various forms of the vernacular existence, including urban vernaculars. The focus is on the consideration of the features characterizing language variations at phonological and phonetic levels. This is caused by the necessity of determining sources and patterns of linguistic variations at the phonetic level, one of which, in our opinion, may be the nonstandard dialect as one of the forms of language existence. The article touches upon such notions as: colloquial language, regional norms and regional peculiarities of pronunciation. The article presents some pronunciation peculiarities of Cologne inhabitants’ urban colloquial speech at the segmental level of the German language phonetic system.