Abstract
The coupling of waves between the piezoelectric generators, detectors, and propagating media is challenging due to mismatch in the acoustic properties. The mismatch leads to the reverberation of waves within the transducer, heating, low signal-to-noise ratio, and signal distortion. Acoustic impedance matching increases the coupling largely. This article presents standard methods to match the acoustic impedance of the piezoelectric sensors, actuators, and transducers with the surrounding wave propagation media. Acoustic matching methods utilizing active and passive materials have been discussed. Special materials such as nanocomposites, metamaterials, and metasurfaces as emerging materials have been presented. Emphasis is placed throughout the article to differentiate the difference between electric and acoustic impedance matching and the relation between the two. Comparison of various techniques is made with the discussion on capabilities, advantages, and disadvantages. Acoustic impedance matching for specific and uncommon applications has also been covered.
Highlights
Piezoelectric materials serve with a wide variety of applications when used in many ways
Most of the transducers used in biomedical, nondestructive evaluation (NDE), and structural health monitoring (SHM) applications operate based on the principle of piezoelectricity
This review article presented the theory of smart materials in the context of their use in sensors and transducers considering various aspects of acoustic impedance-matching layer design
Summary
Piezoelectric materials serve with a wide variety of applications when used in many ways. The material properties of the piezoelectric element are modified to assist with the acoustic impedance matching. Depending on the requirements of an application and limitations arising due to the design constraints of the electric and acoustic elements of the transducer system, the acoustic impedance matching procedure may be dependent or independent. The independent design involves the matching of acoustic impedance of piezoelectric element(s) to the wave propagating medium. Many techniques have been reported so far to match the acoustic impedance of piezoelectric element with the wave propagating medium These techniques involve changing the geometry or material property of the matching layer or the piezoelectric element itself (for example, piezocomposites with varying filler or fiber content).
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