Under slow to normal acceleration my car makes a deep noise and vibrates between 20 and 30 miles per hour. It sounds like some kind of tire noise and also happens when I'm slowing down. What could it be? The steering wheel doesn't shake when it happens. I just lowered my car and it got worse so that's why I'm asking. It used to be okay, but now it's rediculous.

Okay after some research....yeah I should have done it before posting sorry....I'm guessing my tires are feathered....I think. They have less than 20k on them for sure. What causes this? Any way to prevent it with my new tires?

Wheel alignment and camber kit.

^ +1...I get my car aligned every 6 months and at the same time have it balanced.

your tires are uneven wear out!!

What kind of tires are you running? For example, 20K on a set of Bridgestone Potenza RE050A's is a lot of miles - they only have a 140 treadwear rating