Submillimeter Acoustic Vibration Measurement and Monitoring Using a Single Smartphone

The accurate vibration measurement is crucial for monitoring and diagnosing industrial equipment. Existing solutions require either installing contact sensors on the equipment or using noncontact sensors such as laser. Both approaches involve complex deployment, stringent environmental conditions, and high cost. As a better alternative, we propose a submillimeter acoustic vibration measurement system using a single smartphone, called Mobile-Vib. First, we develop a novel acoustic ranging method that builds on traditional acoustic ranging techniques, incorporating the reflection principle of acoustic signals from vibrating objects. This approach addresses the challenge of acoustic signal refresh rate in vibration measurement by employing advanced signal design and processing techniques. Second, we design a noise removal algorithm utilizing the dual-channel technology of smartphones to minimize multipath signals and noise interference, enabling accurate phase estimation. To mitigate the impact of unrelated human motions in real-world measurements, we implement an optimization-based method to correct distortions and reduce errors. Finally, by clarifying the relationship between phase changes and actual displacement, we enable tracking of vibration displacement in industrial environments. We have implemented Mobile-Vib, and the extensive experimental results demonstrate an average error of approximately 0.629 mm in displacement estimation and 5.6 Hz in frequency estimation at a 1-m distance from the vibrating object in real industrial vibration monitoring scenarios.