I was on my front porch looking at my phone when I suddenly hear a low rumbling noise that began to slowly get louder. At first being near Baton Rouge with our chemical plants, I thought the noise was the plant kicking up their flame stacks to burn more chemicals. Sometimes at night they do this and you can hear it for about 30 minutes to an hour. I walked out to get a better idea of which direction it was coming from and immediately noticed a group of flashing lights in the sky. I knew this couldn't be airplanes flashing in the distance because of first off the lights were in a triangle shape and they were all the same distance from me. Also the lights were flashing in sequential order from left to right in perfect timing. I watched as the sound got louder and then noticed they were all moving together towards northwest from original location I spotted it in. The lights lead me to believe instead of 5 different objects, this was one very large object. As large as maybe half of my town of Zachary Louisiana. Roughly 4 miles across. As it moved away I ran and woke my mother to have a second witness. My mom does not believe in UFOs and she was also convinced it was one large triangle. As it got further away the rumbling stopped and also the front light became solid and stayed on until no lights were visible. I would LOVE to know if anything was reported on Radar being I live near Baton Rouge airport. This also means I am used to flashing lights from planes and also study passing satellites and orbiting rocket bodies using a sky monitoring app for satellites in the sky. Lots of cloud cover tonight but clouds were very high. I did not see any single planes tonight though. These were the only lights. I always see strange objects because I watch the skys. I have seen more than one anomalies in the same direction from my front yard. But this was the first ever hearing anything and first triangle craft or at least formation.