This text, an introduction to geophysical signal analysis, is concerned with the construction, analysis, and interpretation of mathematical and statistical models. In general, it is intended to provide material of interest to upper undergraduate students in mathematics, science, and engineering. Much of this book requires only a knowledge of elementary algebra. However, at some points, a familiarity with elementary calculus and matrix algebra is needed. The practical use of the concepts and techniques developed is illustrated by numerous applications. Care has been taken to choose examples that are of interest to a variety of readers. Therefore, the book contains material of interest to both geophysicists and those engaged in digital signal analysis in disciplines other than geophysics. This book is a reprint of the 1980 Prentice-Hall volume of the same title.