Noisy mast

[hperros]

My mast has a ghost in it. When the boat is at the dock or anchored out and it is a little windy, the mast makes a deep noise like a giant blowing through a large pipe or like a factory running nearby. It also creates harmonics if it gets windier. Also, there is vibration. The vibration does not go away when I loosen all the halyards . The vibration is not very common, but the deep sound is always there even in a 10 mile wind. Also, when I sail and the wind picks up, the mast sometimes makes a high-pitched noise. I have not been able to find any discussion in the forum on this topic. Is this noise due to the open slot in the back of the mast??

[hperros]

Follow-up
I tightened the forward lower shrouds by half a turn and the vibration is gone.
Peace at last !!