Many studies have used various time-frequency feature extraction methods to convert ship-radiated noise into three-dimensional (3D) data suitable for computer vision (CV) models, which have shown good results in public datasets. However, traditional feature engineering (FE) has been enhanced to interface matching–feature engineering (IM-FE). This approach requires considerable effort in feature design, larger sample duration, or a higher upper limit of frequency. In this context, this paper proposes a one-dimensional network design for underwater acoustic target recognition (UATR-ND1D), only combined with fast Fourier transform (FFT), which can effectively alleviate the problem of IM-FE. This method is abbreviated as FFT-UATR-ND1D. FFT-UATR-ND1D was applied to the design of a one-dimensional network, named ResNet1D. Experiments were conducted on two mainstream datasets, using ResNet1D in 4320 and 360 tests, respectively. The lightweight model ResNet1D_S, with only 0.17 M parameters and 3.4 M floating point operations (FLOPs), achieved average accuracies were 97.2% and 95.20%. The larger model, ResNet1D_B, with 2.1 M parameters and 5.0 M FLOPs, both reached optimal accuracies, 98.81% and 98.42%, respectively. Compared to existing methods, those with similar parameter sizes performed 3–5% worse than the methods proposed in this paper. Additionally, methods achieving similar recognition rates require more parameters of 1 to 2 orders of magnitude and FLOPs.

Given the inherently three-dimensional (3D) nature of practical underwater applications, this study investigates the influence of geometric factors on the acoustic absorption performance of three-dimensional dual-graded anechoic coatings (3D DGAC). The 3D DGAC is confirmed to exhibit markedly different acoustic absorption performance compared to its two-dimensional counterpart, despite having identical characteristic lengths. A full parametric study of 729 spherical configurations highlights the importance of geometric gradation, particularly the effect of the first cavity’s size, in determining absorption performance. The 3D DGAC can retain high sound absorption efficiency even with slight deviations from the ideal graded arrangement. An orthogonal array-based analysis of block-shaped inclusions arranged in a cuboid lattice further reinforces the significance of geometric gradation for achieving effective sound absorption. This study provides valuable guidance for the design of 3D underwater anechoic coatings.