In the fields such as evacuation guidance and entertainment, it is important for each listener to provide different sound information by using some loudspeakers in a same room. However, listeners have difficulty obtaining target sound information because various sound signals are mixed by using a general loudspeaker which has a wide directivity. To solve this problem, a parametric loudspeaker w...

In part one of this series of articles, level measurement using a floating system was discusses and the instruments were recommended for each application. In the second part of these articles, level measurement with the aid of pressure instruments was discussed. In the third part of this series of articles, radar level measurement basics and parameters affecting its efficiency were explained an...

Detection of fatigue cracks originating from fastener holes is an important application for structural health monitoring (SHM) of civil, mechanical and aerospace structures, but their detection via ultrasonic guided waves can be problematic when cracks are tightly closed in the absence of applied tensile loads. Proposed here are load-differential guided wave methods, which compare signals at on...

Abstract Ultrasonic inspection is a well recognized technique for non-destructive testing of aircraft components. It provides both local highly sensitive in the vicinity sensor and long-range structural assessment by means guided waves. In general, properties ultrasonic waves like velocity, attenuation propagation characteristics such as reflection, transmission scattering depend on composition...

This paper presented development work of an in situ method for damage detection in thin-wall structures using embedded two-dimensional ultrasonic phased arrays. Piezoelectric wafer active sensors were used to generate and receive guided Lamb waves propagating in the plate-like structure. The development of a generic beamforming algorithm that does not require parallel ray assumption through usi...

Nondestructive evaluation (NDE) of aerospace structures using traditional methods is a complex, time-consuming process critical to maintaining mission readiness and flight safety. Limited access to corrosion-prone structure and the restricted applicability of available NDE techniques for the detection of hidden corrosion or other damage often compound the challenge. In this paper we discuss our...

Similar to pulse-echo ultrasound, optoacoustic imaging encodes the location of optical absorbers by the time-of-flight of ultrasound waves. Yet, signal generation mechanisms are fundamentally different for the two modalities, leading to significant distinction between the optimum image formation strategies. While interference of back-scattered ultrasound waves with random phases causes speckle ...

We design a device for the passive mode conversion of guided, axisymmetric, ultrasonic waves in hollow elastic pipes into arbitrary non-axisymmetric flexural that have constant angular profile along pipe axis. To achieve this we create an analogue to optical spiral phase plates - pipe. Three possible configurations are presented which allow efficient generation from longitudinal forcing. The th...

Based on rigorous theoretical findings, we present a proof-of-concept design for a structured square cloak enclosing a void in an elastic lattice. We implement high-precision fabrication and experimental testing of an elastic invisibility cloak for flexural waves in a mechanical lattice. This is accompanied by verifications and numerical modelling performed through finite element simulations. T...

It is important to examine the factors that determine the properties of graphene. Various factors affect the properties of graphene nanosheets that can revolutionize the use of graphene. One such factor is ultrasonic waves, which have significant effects on graphene properties. In this research, we studied the effect of ultrasonic waves with different power levels (35, 50, 360, and 420 W) on fo...