Acoustic-based localization aims to determine target proximity, localize them, and track their movement over time. In most cases, these applications rely on measuring the timing of received acoustic waves, whether reflected or directly received, and using the known speed of sound in the medium to compute distances or angles. This chapter examines location services enabled by active acoustic sensing, encompassing ranging, localization, and tracking. By analyzing state-of-the-art methodologies, we systematically demonstrate how the fundamental principles introduced in Chap. 3 are applied. Additionally, we highlight key techniques designed to mitigate the challenges associated with acoustic sensing, as discussed in Chap. 2 .