Coming out from behind

2002 model 206 has no problem, you can hear the sound coming from the back for the last week, so you can hear it very slowly, even after it stops, what can this be about?

If it is a high pitched whistling sound, I also have exhaust, I think it may be exhaust or vibration or rubbing on one of your feet, hojam.

I found it coming from inside the gas tank, shake back

I have that voice, but I thought it was coming from the wheel, like a ball sound. As if there is a bird behind,