The attenuation of ultrasonic waves is commonly used as a measure to characterize the porosity content in composite laminates [4–9]. For plane plate specimens, the quantitative evaluation of attenuation coefficient is possible by the calibration accounting for the ultrasonic beam diffraction and the insertion loss due to the difference of acoustic impedances between the laminate and the coupling medium, e.g., see Ref. [24]. For curved laminates considered here, however, such procedures are not straightforward, and therefore a simplistic approach is chosen. Namely, the amplitude ratio of the surface and bottom echoes in the reflection waveform is examined as a measure of ultrasonic wave attenuation. From the reflection waveforms measured on five different locations along the longitudinal direction of each corner specimen, the ratios of the maximum peak-to-peak height of the surface and bottom echoes were calculated. These ratios are plotted in Fig. 10 against the porosity content for (*a*) the unidirectional and (*b*) the quasi-isotropic laminates using two kinds of focusing transducers. In Figs. 10(a) and 10(b), the amplitude ratios show the decreasing trend with the porosity content, indicating that the porosity-content estimation is possible based on these relations. It should be noted here that the porosity contents in Fig. 10 were measured on the edge faces of the specimens and do not represent the local porosity contents corresponding to the waveform measurements: plotting the amplitude ratios against the local porosity contents could improve the correlation quantitatively.