- Conference date: 10–13 September 2008
- Location: Minneapolis (Minnesota)
The lossless impulse response method models transient wave propagation generated by finite apertures, including focused radiators, while neglecting frequency‐dependent attenuation. Therefore, an analytical time‐domain expression that incorporates loss, diffraction, and focusing is needed for calculations of transient pressures produced by spherical shells in attenuating media. To derive an impulse response expression in lossy media, the Green’s function to the Stokes wave equation, which models viscous loss, is decomposed into into diffraction and loss factors. By utilizing a previously derived fast nearfield expression for a baffled, spherical shell, a single integral expression, involving the error function, is derived for the lossy impulse response. This expression generalizes a previous expression that was derived for on‐axis pressures (Djelouah et al., 2003). The resulting impulse response simultaneously accounts for frequency‐squared dependent attenuation and diffraction and is straightforward to evaluate numerically. Transient fields, both on and off‐axis, are produced by convolving the lossy impulse response with a known incident pulse. The effect of frequency‐squared attenuation on focusing is evaluated, thereby facilitating transducer modeling in lossy media.
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