Ugly hum, roaring from about 4800 1/min

Hi, from about 4800 up to the red area I have a roaring and roaring. Somehow I also think of detonators. I notice it most in the 2nd gear, but also in the 3rd gear. The friendly one hears it but also not what it could be. One means the roaring comes from the engine room in driving direction to the right. The car runs in the 5th gear nevertheless about 245 lt Tacho then without the noise. Can something have been solved? Does anyone have any idea what it might be? Greeting Hardi