Noise as a murmur by increasing speed

Greetings to all colleagues.
I would like to have what kind of problem I can have. Since I have a Renault Megane 1.5 dci Luxe Privile. The fact is that when I start up, I gradually increase the speed I hear as if it were a murmur of the asta engine that stable a constant speed, I do not know if it will be of the transmission or that causes it can be, or you want the rear pads, the truth is that I do not know.
I would appreciate that they would help me. please.

I don't know if I understood well, but when the speed is stabilized, noise disappears you have a transmission problem