I've seen anything from aerodynamic issues to an object lodged in the exhaust manifold. If the problem becomes a nuisance or it worsens, go to an auto repair shop.
Check under your car... you may have lost a muffler.
I think it,s louder inside the car
they are faster, louder and can kill a child alot quicker than a duracell powered car
talk louder or you change the tone setting of your bluteeth earphone on your bluetooth car kit!
Dpending on how close you are and what frequencies are listened to, either can be louder.
A worn serpentine belt will make a high-pitched squeal when the engine is running. The faster you go, the louder the high-pitched will become.
It is moving in the positive direction at a rate which is increasing.
Well depends on the car... On a car with a turbo charger that is what you are hearing. Or, I've heard whistles coming from exhaust leaks as well as those little prank whistles you can stick in the back of exhaust.
Warped brake discs? Drive shaft? Rear axle?
Yes, most cars are.
Bad bearing in a belt driven accessory? i.e. alternator, water pump, idler pulley, belt tensioner, etc.?
The engine usually gets louder? Shift+/