Acoustic logging is a multidisciplinary technology involving basic theory, instrumentation, and data processing/interpretation methodologies. The advancement of the technology now allows for a broad range of measurements to obtain formation properties such as elastic wave velocity and attenuation, formation permeability, and seismic anisotropy that are important for petroleum reservoir exploration. With these advances, it is easier to detect and characterize formation fractures, estimate formation stress field, and locate/estimate petroleum reserves. The technology has evolved from the monopole acoustic logging into the multipole, including dipole, cross-dipole, and even quadrupole, acoustic logging measurements. The measurement process has developed from the conventional wireline logging into the logging-while-drilling stage. For such a fast developing technology with applications that are interesting to readers of different backgrounds, it is necessary to have systematic documentation of the discipline, including the theory, methods, and applications, as well as the technology's past, present, and near future development trends. "Quantitative Borehole Acoustic Methods" provides such documentation, with emphasis on the development over the past decade. Although considerable effort has been made to provide a thorough basis for the theory and methodology development, emphasis is placed on the applications of the developed methods. The applications are illustrated with field data examples. Many of the acoustic waveform analysis/processing methods described in the book are now widely used in the well logging industry.