Love the dryer balls...I have 5...don't know where that 6th one is...(probably folded in a sheet!) But when I dry the clothes late at night, we can hear them banging around a little. Of course, our dryer is in the garage & our bedroom is right over the dryer. We still sleep though.
I hate smells--pretty or otherwise!, so I use white vinager in the fabric softener cup & if I need a little extra whitening, I have started using Hydrogen Peroxide in the bleach cup.
My clothes have been coming out just fine, saved a ton of $$ on the softener, bleach, sheets, etc. Costco sells white vinager in 1 1/2 gallons for about $4, & the vinager helps brighten colors--elimating the need for Clorox 2 & softens clothes, elimating the need for both liquid & sheet softeners. Also saves on repair bills, the washer repair dude told me a long time ago to NEVER use liquid softener, as it gums up the insides of the washer & can cause really costIy repairs.
I bought a set of reusable static eliminator dryer sheets 2 or 3 years ago & I just leave them in the dryer with the balls. If I wash nylon or fleece, then if I've not re-charged them for a while, I'll notice some static, although not bad & I just wash the sheets with the next load. I think they are SO worth the $$.
BTW, if you have a front load washer, the vinager in the wash also seems to keep the mold problem away.