Muffler Like Sound

[gkb]

Hi All,

Im a newbie to this forum.

My question is...... i have a 2003 toyota avensis and when i start it in the mornings or after a long period being off, it makes an extremely loud sound through the exhaust.

After the engine warms up, the sound decreases. i still however still get a "muffler" sound when driving.

I've seen and heard similar cars drive and i dont hear that sound. (im not sure about others with the startup noise)

Are there any suggestions as to what would cause that muffler sound while driving? my mechanic said its normal for cars with this type of engine, but im sure that something can be done to rid the car of that "noise".