Spatiotemporal Deconvolution of Hydrophone Response for Linear and Nonlinear Beams II: Experimental Validation

This article reports experimental validation for spatiotemporal deconvolution methods and simple empirical formulas to correct pressure and beamwidth measurements for spatial averaging across a hydrophone sensitive element. The method was validated using linear and nonlinear beams transmitted by 7 single-element spherically focusing transducers (2–10 MHz; F/#: 1–3) and measured with 5 hydrophones (sensitive element diameters d g : 85–1000 μm), resulting in 35 transducer / hydrophone combinations. Exponential functions, exp(−αx), where x= d g /(λ 1 F/#) and λ 1 is fundamental wavelength, were used to model focal pressure ratios p ’/ p (where p’ = measured value subjected to spatial averaging and p = true axial value that would be obtained with a hypothetical point hydrophone). Spatiotemporal deconvolution reduced α (followed by root mean squared difference between data and fit) from 0.29–0.30 (7%) to 0.01 (8%) (linear signals) and from 0.29–0.40 (8%) to 0.04 (14%) (nonlinear signals), indicating successful spatial averaging correction. Linear functions, Cx +1, were used to model FWHM’/FWHM, where FWHM is full width half maximum). Spatiotemporal deconvolution reduced C from 9% (4%) to −0.6% (1%) (linear signals) and from 30% (10%) to 6% (5%) (nonlinear signals), indicating successful spatial averaging correction. Spatiotemporal deconvolution resulted in significant improvement in accuracy even when the hydrophone geometrical sensitive element diameter exceeded the beam FWHM. Responsible reporting of hydrophone-based pressure measurements should always acknowledge spatial averaging considerations.