Slightly noticeable rhythmic wheel rumble
I recently had a wheel alignment and new PS2's put on the rear tires only. The other day while driving at very low speed in a parking lot and also on a side street (below 15 mph) I noticed a barely perceptible wheel rumble/noise that seemed to increase/decrease in frequency as the car increased/decreased speed. It almost sounds like a very slight but barely noticeable rubbing sound - it is not noticeable at all at times, and when it is it is so subtle that I am not sure if I'm actually hearing something or if it's my imagination.
When I took my car in the SA said he noticed some slight "feathering" of the front tires, which prompted him to recommend a wheel alignment (and which I agreed to). My car has over 14k miles on it. The SA did not specifically recommend new front tires - instead I only asked to have the rears replaced, since the tread depth indicators were even with the contact surface of the tires, whereas there was still extra tread depth on the front tires beyond the tread wear indicators.
After getting the new PS2's on the rear wheels and wheel alignment, I noticed this rubbing, rhythmic sound referenced above. Does anyone think that it may be related to the fact that the front tires wore in a specific pattern before the alignment, and now after the alignment has been done, the tires are hitting the pavement in a different "pattern" than before the alignment (thus creating this barely noticeable sound)? Is it possibly a wheel balancing issue?
Either way, I'm going to take it back in soon to have an SA ride in the car with me to try and see if there is a problem (or if this is normal or just my imagination). Either way, any feedback (pun not intended) in the meantime would be appreciated. Thanks,