An unknown craft gave off a loud, deep, oscillating, electro-acoustic, bass humming sounds.

I had a close encounter with an unknown shaped craft.  The craft gave off a loud, deep, oscillating, electro-acoustic, bass, humming sound that came from the sky.  The bass from the craft oscillated slowly and became louder and deeper and began to shake me and the ground.  The craft came very close during the encounter and appeared to be on the ground in front of me and another approximately 40yrds away.  I do not know if it was the same craft in the sky or something different that approached the two of us.  I could go further into what happened next, but I will reserve the right not to continue.   I will say this, if I could of saw what approached the two of us I probably would not have stuck around.  I am glad I did because I know that there is more out there than meets the eye.