Abstract
With advancements of wireless and sensing technologies, recent studies have demonstrated technical feasibility and effectiveness of using acoustic signals for sensing. In the past decades, low-cost audio infrastructures are widely-deployed and integrated into mobile and Internet of Things (IoT) devices to facilitate a broad array of applications including human activity recognition, tracking, localization, and security monitoring. The technology underpinning these applications lies in the analysis of propagation properties of acoustic signals (e.g., reflection, diffraction, and scattering) when they encounter human bodies. As a result, these applications serve as the foundation to support various daily functionalities such as safety protection, smart healthcare, and smart appliance interaction. The already-existing acoustic infrastructure could also complement RF-based localization and other approaches based on short-range communications such as Near-Field Communication (NFC) and Quick Response (QR) code. In this paper, we provide a comprehensive review on acoustic-based sensing in terms of hardware infrastructure, technical approaches, and its broad applications. First we describe different methodologies and techniques of using acoustic signals for sensing including Time-of-Arrival (ToA), Frequency Modulated Continuous Wave (FMCW), Time-Difference-of-Arrival (TDoA), and Channel Impulse Response (CIR). Then we classify various applications and compare different acoustic-based sensing approaches: in recognition and tracking, we review daily activity recognition, human health and behavioral monitoring hand gesture recognition, hand movement tracking, and speech recognition; in localization and navigation, we discuss ranging and direction finding, indoor and outdoor localization, and floor map construction; in security and privacy, we survey user authentication, keystroke snooping attacks, audio adversarial attacks, acoustic vibration attacks, and privacy protection schemes. Lastly we discuss future research directions and limitations of the acoustic-based sensing.