The response of materials and the functioning of devices is often associated with noise. In this book, Stefano Zapperi concentrates on a particular type of noise, known as crackling noise, which is characterized by an intermittent series of broadly distributed pulses. While representing a nuisance in many practical applications, crackling noise can also tell us something useful about the microscopic processes ruling the materials behavior. Each crackle in the noise series usually corresponds to a localized impulsive event, an avalanche, occurring inside the material. A distinct statistical feature of crackling noise, and of the underlying avalanche behavior, is the presence of scaling, observed as power-law distributed noise pulses, long-range correlation, and scale free spectra. These are the hallmarks of critical phenomena and phase transitions. This work summarizes the current understanding of crackling noise, reviewing research undertaken in the past 30 years, from the early and influential ideas on self-organized criticality in sandpile models, to more modern studies on disordered systems. Crackling Noise covers the main theoretical models used to investigate avalanche phenomena, describes the statistical tools needed to analyze crackling noise, and provides a detailed discussion of a set of relevant examples of crackling noise in materials science. These include acoustic emission in fracture, strain bursts in amorphous and crystal plasticity, granular avalanches, magnetic noise in ferromagnets and superconductors, and fluid flow in porous media. The book concludes by considering the wider application of these models in the natural sciences.