After speed bumper, it sounds like it has a flat-tire
 

Tonight, I went to the gas station, and when I left gas station, I need
to speed up little bit to get to the lane which I need to make a left
turn. But, when I jumped into the road, there was something like speed
bumper, my car didn't hit any of that bumper -I didn't hear any sounds.

But just after I jumped in to road, I hear the flat-tire sound from my
car. If I drive it fast, the interval of the sounds is getting faster,
same way when I drive it slow, its interval is getting slow.

First time, I thought that was a tire problem. I stopped my car and
checked it but there was NO flat tire. All the tire was okay. But,
again, after I inspect my tire, I still heard same sounds.

I speed up little bit ( 30 mph), and suddenly, the flat-tire-like sound
were gone. So, it is okay so far till now. But, I'm worrying about it
if something critical happened to my car.

Anyone have same experience? Anyone can help me?

Thanks.