Unobtrusive Pedestrian Identification by Leveraging Footstep Sounds with Replay Resistance

The ability to identify pedestrians unobtrusively is essential for smart buildings to provide customized environments, energy saving, health monitoring and security-enhanced services. In this paper, we present an unobtrusive pedestrian identification system by passively listening to people's walking sounds. The proposed acoustic system can be easily integrated with the widely deployed voice assistant devices while providing the context awareness ability. This work focuses on two major tasks. Firstly, we address the challenge of recognizing footstep sounds in complex indoor scenarios by exploiting deep learning and the advanced stereo recording technology that is available on most voice assistant devices. We develop a Convolutional Neural Network-based algorithm and the footstep sound-oriented signal processing schemes to identify users by their footstep sounds accurately. Secondly, we design a "live" footstep detection approach to defend against replay attacks. By deriving the novel inter-footstep and intra-footstep characteristics, we distinguish live footstep sounds from the machine speaker's replay sounds based on their spatial variances. The system is evaluated under normal scenarios, traditional replay attacks and the advanced replays, which are designed to forge footstep sounds both acoustically and spatially. Extensive experiments show that our system identifies people with up to 94.9% accuracy in one footstep and shields 100% traditional replay attacks and up to 99% advanced replay attacks.

Using the automated Verasonics system for physical modeling of skeletal muscle biomechanics

The paper describes the use of the Verasonics research system for physical modeling of skeletal muscle biomechanics. The scheme of the acoustic system is described. The path of receiving and processing the signal is presented. A brief overview of the operation of software algorithms for the implementation of methods of ultrasound diagnostics is made. A mathematical model of skeletal muscle as a flat-layered medium is considered. The implementation of this model in the form of a fibers agar phantom is proposed. Using the Verasonics acoustic system shear velocities of physical fibers agar phantom were measured. Shear modules for agar and fibers were calculated. The obtained values are consistent with similar characteristics of native muscles and connective tissue fibers.

Topological pumping in acoustic waveguide arrays with hopping modulation

Thouless pumping is the adiabatic transportation of quantized charge, which is regarded as the dynamic version of the quantum Hall effect. Here we propose the design of an acoustic system to demonstrate the topological pumping characterized by transporting acoustic energy from one side to the opposite. The system is composed of coupled acoustic waveguide arrays with modulated coupling along both cross-sections and the propagating direction. We explore multiple topological phases by introducing rich spatial frequency or enlarged range of the hopping modulation. Such distinct topological phases are evidenced by adiabatic evolution of the edge states, where the acoustic system varies continuously and slowly along the state propagating direction. The robustness behavior of the edge states transport is also verified with numerical simulations to imply their topology origin. Our work provides a route to realize topological phases and utilize the corresponding edge states in waveguide arrays that can lead to versatile acoustic wave manipulation applications.

The Acoustic System of the Fendouzhe HOV

Due to the strong absorption and attenuation of electromagnetic waves by water, radio communications and global positioning systems are lacking in the deep-sea environment. Therefore, underwater long-distance communications, positioning, detection and other functions depend on acoustic technology. In order to realize the above functions, the acoustic system of the Fendouzhe human occupied vehicle (HOV) is composed of eight kinds of sonars and sensors, which is one of the core systems of manned submersible. Based on the Jiaolong/Shenhai Yongshi HOVs, the acoustic system of the Fendouzhe HOV has been developed. Compared with the previous technology, there are many technical improvements and innovations: 10,000-m underwater acoustic communication, 10,000-m underwater acoustic positioning, multi-beam forward-looking imaging sonar, an integrated navigation system, etc. This study introduces the structure of the acoustic system of the Fendouzhe HOV and the technical improvements compared with the Jiaolong/Shenhai Yongshi HOVs. The results of the acoustic system are illustrated by the 10,000-m sea trails in the Mariana Trench from October to December 2020.

Design and Experimental Study of the Rolling Enhanced Acoustic System for Gear Tooth Surface

Parameters of gear flanks, such as roughness, hardness, and residual stress, impact their working performance. Therefore, it is essential to optimize these parameters for increasing gears’ life. Thus, this study combined the meshing theory and the ultrasonic surface rolling technology, and presented an innovative design to realize ultrasonic burnishing. First，the dimensions of the ultrasonic burnishing device with two nodes integrated with a gear at the bottom were calculated using frequency equations by a numerical method. Second the correctness of the calculating results was verified by simulations and experiments. Third, the influence of the ratio between the width and diameter of the gear on the acoustic system was studied. Finally, experimental platform of the rolling enhanced acoustic system for gear tooth surface is built successfully. A series of experiments were conducted, and the results showed that the roughness decreased and the hardness and the residual stress improved. Therefore, this design provided a new theory and technology to machine complicated surfaces such as gear flanks.

A Novel Sparse Polynomial Expansion Method for Interval and Random Response Analysis of Uncertain Vibro-Acoustic System

For the vibro-acoustic system with interval and random uncertainties, polynomial chaos expansions have received broad and persistent attention. Nevertheless, the cost of the computation process increases sharply with the increasing number of uncertain parameters. This study presents a novel interval and random polynomial expansion method, called Sparse Grids’ Sequential Sampling-based Interval and Random Arbitrary Polynomial Chaos (SGS-IRAPC) method, to obtain the response of a vibro-acoustic system with interval and random uncertainties. The proposed SGS-IRAPC retains the accuracy and the simplicity of the traditional arbitrary polynomial chaos method, while avoiding its inefficiency. In the SGS-IRAPC, the response is approximated by the moment-based arbitrary polynomial chaos expansion and the expansion coefficient is determined by the least squares approximation method. A new sparse sampling scheme combined the sparse grids’ scheme with the sequential sampling scheme which is employed to generate the sampling points used to calculate the expansion coefficient to decrease the computational cost. The efficiency of the proposed surrogate method is demonstrated using a typical mathematical problem and an engineering application.