Really weird growling noise in minecraft? o_o?

hey guys, so i was mining in minecraft and i was about 10 blocks down and all of a sudden i started hearing a noise like this a href="http://www.youtube.com/watch?v=FdZqR7CBhMM" rel="nofollow"http://www.youtube.com/watch?v=FdZqR7CBh…/a . the thing is, i don't have that mod and i don't know what it is, lmao. what is it? thank you so much c: