Could I suggest this - while pushing up/down on the body or bumper, watch the upper strut mounts and listen or have someone else do the pushing. Also try wiggling them around. On mine the rubber bushings started to crack visibly before the rubber fully split.

I think I could hear the noise best during a slow banked turn or when driving down a bumpy alleyway between buildings that reflected sound, with windows open.

I haven't personally had a strut or shock fail without it leaking visibly or suddenly falling apart entirely.