As the application of wideband acoustic immittance (WAI) becomes more widespread, it is important to recognize how different middle ear pathologies impact absorbance patterns. The purpose of this chapter is to cover the general principles of absorbance/reflectance techniques and examine absorbance patterns in normal middle ear condition and different middle ear pathologies in newborns, children, and adults. The impact of different middle ear pathologies, such as negative middle-ear pressure (MEP), tympanic membrane perforation, middle-ear with effusion, ossicular abnormalities, on absorbance patterns will be summarized and, when appropriate, will be compared with age-appropriate normative data. Moreover, the impact of the pressurization wideband tympanometry (WBT) on absorbance patterns will be reviewed and compared with traditional tympanometric results.