Diffraction correction in high-precision pulse-echo and multiple-reflection ultrasonic measurement systems for fluids.

In high-precision ultrasonic measurement systems, diffraction correction models accounting for electrical and mechanical boundary conditions may be needed, as shown in prior work using a finite element diffraction correction (FEDC) model for one-way transmit-receive systems. Such descriptions may also be needed for pulse-echo and multiple-reflection ultrasonic measurement applications. The FEDC model is here generalized to n-way measurement systems (n = 1, 2, 3,…) using coaxially aligned piezoelectric transducers in a fluid medium.

A spectrum-of-spectrum filtering method to extract direct and multipath arrivals from simulations and measurements.

In measurements and numerical modelling of wave propagation, undesired interference between direct and multipath arrivals can be reduced using Fourier-based signal processing methods. Existing methods, such as cepstral analysis and time-signal gating, are not applicable to all cases. Here, an alternative Fourier-based signal processing method is presented, called spectrum-of-spectrum (SoS) filtering.

Finite element-based diffraction correction for piezoelectric transducers accounting for diffraction at transmission, propagation, and reception.

Existing diffraction correction models for ultrasonic transmit-receive measurement systems rely on simplifying assumptions with respect to the boundary conditions at the transmitter or receiver. Common simplifications include approximating the sound field radiated by a piezoelectric transducer using a baffled piston model and assuming that the receiver's electrical response is proportional to the spatially averaged free-field pressure over its front surface. In many applications, such simplifications may be adequate, but their validity and accuracy need to be evaluated and quantified.

Finite element modeling of ultrasound measurement systems for gas. Comparison with experiments in air.

Quantitative modeling of ultrasound measurement systems is of considerable value for design, analysis, and interpretation of measurements, methods, and systems. In this work, a model is developed for description of transmit-receive measurement systems based on radial-mode transducer operation in a homogeneous fluid medium. Axisymmetric finite element (FE) modeling is used for the transmitting and receiving piezoelectric transducers and sound propagation in the medium.