Air-coupled ultrasound is a well-established tool for acoustic NDT and material characterization. Its major shortcoming is concerned with a weak penetration into material due to a severe impedance mismatch at the air-solid interface. A strong rise in acoustic coupling to solids is obtained by using acoustic mode conversion in slanted configurations. In our experiments, a substantial increase of...

Mathematical analysis of the acoustic wave propagation along coaxial waveguide, whose right part outer wall is impedance-coated, considered. By determining boundary conditions corresponding to relevant geometry, value problem solved by applying Mode-Matching technique. At end analysis, numerical computations are carried out illustrate affect some parameters. The results demonstrate significance...

The acoustic impedance at the diaphragm of an electroacoustic transducer can be varied using a range of basic electrical control strategies, amongst which are electrical shunt circuits. These passive shunt techniques are compared to active acoustic feedback techniques for controlling the acoustic impedance of an electroacoustic transducer. The formulation of feedback-based acoustic impedance co...

The acoustic behaviour of wind instruments is largely determined by their acoustic impedance spectrum measured at the embouchure or 'input' to the instrument. The acoustic impedance Z is the ratio of acoustic pressure p U and its extrema identify the frequencies of resonances and antiresonances due to standing waves in the bore. (For example see [1].) Backus [2] reports measurements of the acou...

A method is developed for measuring acoustic impedance. The method employs a one-dimensional tube or duct with excitation at one end and an unknown acoustic impedance at the termination end. Microphones placed in the tube are then employed to measure the frequency response of the system from which acoustic impedance of the end is calculated. This method uses fixed instrumentation and takes adva...

Also, the power-handling capacity of a transmission line is maximum when it is "flat", i.e., operating at low SWR. Lastly, it is important to be able to interconnect a number of different components into a system, and the only way that can be done reliably and predictably is by constraining the reflection coefficients of the various interfaces through impedance matching. Multiple reflections ca...

Acoustic wave transducers act as cooperative targets for passive, wireless sensing by converting an incoming electromagnetic pulse to an acoustic wave whose velocity is dependent, by design, with a given quantity under investigation. The acoustic wave is delayed and emitted back to the measurement electronics as an electromagnetic pulse by direct piezoelectric effect. In the context of sub-surf...