The infrasound field, the science of low-frequency acoustic waves, has developed into a broad interdisciplinary field encompassing academic disciplines of physics and recent technical and scientific developments. In 1996, the United Nations General Assembly adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT), prohibiting atmospheric nuclear explosions worldwide. The infrasound network of the International Monitoring Network (IMS) of the CTBT-Organization has demonstrated its capability for detecting and locating infrasonic sources such as meteorites, volcanic eruptions, earthquakes, auroras, mountain associated waves... Nearly 70% of the global network is now operational and regional cluster arrays are deployed around the globe. Systematic investigations into low-frequency acoustic signals have evidenced an unprecedented potential of the monitoring of infrasonic waves permanently generated by natural and man-made events. Furthermore, recent studies point out new insights on quantitative relationships between observables and atmospheric specifications, and therefore opening new fields into the mathematics of geophysical inverse problems for atmospheric remote sensing. This volume reviews the most important areas of infrasound, with emphasis on the latest researches and applications, e.g. instrumentation, engineering, signal processing, source monitoring, propagation modeling, atmospheric dynamics, global changes, remote sensing methods. Researchers and students will benefit from a comprehensive content of infrasound related topics, where both fundamental and applied topics are discussed by authors from international institutions, all experts in their fields.