jumping RPMs around 60-100kms when i push it harder , lower acceleration due to this issue

Question

I've got a 2001 Honda Civic 1.7L 4cyl. engine with an automatic transmission. My issue with it is mainly I find when accelerating faster, like merging on a highway, if I try to push it until it shifts from 3000 rpms right up to over 5000 rpms (5500-6000ish), it is not a nice sounding shift and I don't really know the cause of it. I'm not trying to race her, but it would be nice to merge on a 90-100 km highway doing more than 75 km/h.