Low slow flying triangle with red and white lights pulsating irregularly and had light humming sound barely heard

This craft was large, triangular and low flying with a light humming noise unlike nothing I’ve ever heard. I had just walked outside for no reason feeling like I needed to look up and saw this. Weirdest encounter and feeling I’ve ever had. After it flew from north, crossing the Ohio river, it flew south in no hurry, much slower than a plane and all of a sudden I made a swooshing noise and I didn’t see it anymore. Very odd and was one of those things that you just know that it’s not a normal occurrence. Kind of hard to explain the feeling but it was surreal.