A downhole installation includes a first pipe layer, a second pipe layer about the first pipe layer, an annulus between the first and second pipe layers, and a geological formation outside of the second pipe layer. A method for evaluating the downhole installation includes: exciting a flexural wave in the first pipe layer using an angled acoustic transmitter; receiving third interface echo data using a plurality of angled acoustic receivers at different locations along the longitudinal extent of the pipe layers; generating acoustic resonance across the thickness of the first and second pipe layers by use of full waveform excitation; receiving the acoustic response wave field generated by the full waveform; identifying a suitable component of the acoustic response wave field; determining if the material outside the second pipe layer is fluid or solid; and analyzing the third interface echo data to thereby evaluate material conditions in the annulus.