(1) Self - Perhaps the voice that we hear the most is our own. God has given us a mind to think and reason, but often the logical, common-sense voice of self can be in conflict with God's voice. The self voice must be disciplined and surrendered to the will of the Spirit.(2) Others - The voices of other people can have a powerful influence in our life. God can can use others to speak to us. The wisdom and guidance of trusted advisers can be valuable, but we need to be sure the voice of others aligns with the Word and with what God has spoken to us in the past. (3) The enemy - The enemy is always seeking to tear down and destroy what God is doing in our lives. He seeks to keep us from hearing and obey God's voice.
I believe that if we're truly seeking to hear God's voice, the Holy Spirit will shield us and make a way for us to hear and draw near to God. Sometimes these other voices will shout the loudest, but if we can be still and use discernment, we will hear that still small voice.