Little is known about the perception of speech sounds by native Danish listeners. However, the Danish sound system differs in several interesting ways from the sound systems of other languages. For instance, Danish is characterized, among other features, by a rich vowel inventory and by different reductions of speech sounds evident in the pronunciation of the language. This book (originally a PhD thesis) consists of three studies based on the results of two experiments. The experiments were designed to provide knowledge of the perception of Danish speech sounds by Danish adults and infants, in the light of the rich and complex Danish sound system. The first two studies report on native adults’ perception of Danish speech sounds in quiet and noise. The third study examined the development of language-specific perception in native Danish infants at 6, 9 and 12 months of age. The book points to interesting differences in speech perception and acquisition of Danish adults and infants when compared to English. The book is useful for professionals as well as students of linguistics, psycholinguistics and phonetics/phonology, or anyone else who may be interested in language.