Peugeot Partner Drive Belt Problems

At first I thought it was just the road surface I was on, but it is happening all the time now. Steady revolving noise, rising and falling like a wheel going round, while cruising at any speed with no gear changing, accelerating or braking...

1/4 drive I have had a second hand box a new clutch fitted but still the noise is there not as bad as it was but still ,as described before,still a whoop whoop noise unless clutch is depressed then it stops,in 1st gear let van idle along a...