Sound in 307 Diesel / Engine?

Friends, Hello, I have a question 1.6 HDI 90 HP New Case 307 As it is known, when I go uphill with my car or when I put on the gas on the straight road, the sound comes out from the engine, and it stops when the gas is left light. what could that sound be?

No answer?

a mechanical sound, or a sound similar to an air outlet. You said the heck, the hell, the forces that came to my mind.