PhD Dissertation Proposal by Tran Ngoc Doan Thu | Acoustic Sensing Using Mobile Devices

Acoustic sensing in mobile devices has been extensively studied in the last few years. For example, by turning smartphones into FMCW sonars, researchers can contactlessly extract location and motion of a target based on the reflected signals. They can even further detect minute displacement and extract vital signals, such as breathing and heart rates. In addition, since audio is a mechanical wave, which requires a medium to travel, its speed carries information of the medium. Previous works have leveraged high-frequency audio signals to detect wind speed and ambient temperature.

In this dissertation proposal, we further improve acoustic sensing in detecting human heart rate and measuring material’s density and elasticity. First, we introduce an acoustic-based heart rate monitoring system that doubles the sensing range compared to state-of-the-art. Moreover, we increase the number of users up to 4 side-by-side people, which was challenging due to signal interference. The proposed method works with both commodity smartphones and smart speakers. Second, we look deeper into sound's characteristics and discover that smartphone's microphones can record sound propagating in both air and solid. Hence, we propose a smartphone-based approach to measure the speed of sound travelling near the solid surface, which is known to reflect the material's density and elasticity, helping to distinguish different types of solid.

Tran Ngoc Doan Thu is a PhD student at the School of Computing and Information Systems, Singapore Management University, supervised by Professor Rajesh Krishna Balan. Her research interests focus on acoustic sensing and signal processing.