Reconstructing effective ultrasound transducer models via distributed source inversion

Abstract

Accurate modeling of ultrasound wave propagation is essential for high-fidelity simulation and imaging in ultrasonic testing. A primary challenge lies in characterizing the excitation source, particularly for transducers with large apertures relative to the acoustic wavelengths. In such cases, non-uniform excitation and spatial interference significantly affect the resulting radiation patterns. This paper proposes a distributed source inversion strategy to reconstruct an effective spatio-temporal transducer model that reproduces experimentally measured wavefields. The reconstructed source model captures aperture-dependent phase and amplitude variations without the need for detailed knowledge of the transducer structure. The approach is validated using directivity measurements on an aluminum half-cylinder, where simulations incorporating the reconstructed source model show close agreement with experimental directivity patterns and waveform shapes. Finally, synthetic studies on reverse time migration and full-waveform inversion demonstrate that accurate transducer modeling is critical for the success of simulation-based imaging and inversion workflows and significantly improves reconstruction quality.

Figures (12)

• Figure 1: Sketch of half-cylinder experimental setup in $[mm]$.
• Figure 2: Time windows for wavelets (gray solid) and signals (blue solid) alongside an exemplary source wavelet (gray dashed) and measured signal (blue dashed).
• Figure 3: Development of the cost function (top), normalized source amplitude distributions (middle), and corresponding directivity pattern (bottom).
• Figure 4: Reconstructed wavelets for DSI 1 (blue) and DSI 2 (green).
• Figure 5: Waveforms of the P-wave arrivals using inverted distributed source models. The angle of the corresponding receiver is depicted in red at the top right of each plot.