This book is not, as its title may seem to promise, an authoritative survey of an established science. Acoustic phonetics is now in its infancy. The time when general agreement will be reached on its principles is still far in the future. That is, we are at that point of its development where the appropriate sort of publication, according to settled custom, would consist of numerous short articles by various workers, reporting on single discoveries or presenting arguments on single points of theory. Only later, when data and discussion had accumulated to such an extent that the well-known phenomena of convergence had begun to show up, would a summary publication normally be in order, a book which could be trusted as a whole and in all but a small fraction of its details. Such a book was Eduard Sievers' Grundzüge der Phonetik, the culmination of decades of study and theorizing, which will never be truly superseded. The present book is certain to be superseded as a whole, and to be proved wrong or to require restatement at so many points that if the circumstances were at all ordinary there would be no justification for covering the ground that it covers in book form either now or for some years to come. But the present situation in acoustic phonetics is so very extraordinary that immediate book publication of a broad survey appears inescapable. There are two main reasons for this. One is the relative unpreparedness of linguists to deal with acoustic data, the other is the sudden, recent, and unpublicized development of the instruments for laboratory acoustic phonetics.