If you start a descent from cruse by reducing pitch and maintaining
rotor speed, what happens to coning forces as compared to cruse?

I have noticed that during a decent in a R22 that you can get a
"Wop-Wop" noise from the main rotor blades. Changing cyclic or
increasing rotor speed a very small amount can make it go away, or at
least not heard from the cockpit. Can someone explain what is
occurring and why?

Thanks,

Eric D