Summer 1979 Wisconsin

summer 1979, i and a close friend went to Jersey Valley near Westby Wisconsin. we went to just do a day camp to have supper, we had finished eating and were talking [ sitting on the ground ] when i / we felt a low rumble through the ground, this rose up in tone to a very low growl, then continued to rise into a bass roar then to a very high scream - one continuous sound, the volume of this sound was incredible. my friend's dog sprang up as if to attack i told him to grab the dog and get in my truck, we picked up everything dowsed the campfire, and got out of there as fast as we could. whatever it was, was only about 30 feet from us in the woods nearby.we did not see the animal itself. we saw nothing, heard nothing, nor smelled anything before the growl/roar/ scream. I've since researched the sound (s) a cougar can make and they cannot roar like the other big cats so it wasn't a cougar. my only thought is it was a bigfoot, there was at least one reported sighting at around that same time in Cashton also in the area, the experience scared us both