The person who asked this question cited two scriptural passages:
And after the earthquake a fire, but the Lord was not in the fire. And after the fire the sound of a low whisper. (1 Kings 19:12)
For a people shall dwell in Zion, in Jerusalem; you shall weep no more. He will surely be gracious to you at the sound of your cry. As soon as he hears it, he answers you . . . And your ears shall hear a word behind you, saying, “This is the way, walk in it,” when you turn to the right or when you turn to the left. (Isaiah 30:19-21)
In the first case, God is speaking to Elijah, and in the second case he is speaking to his people living in Jerusalem. Although they sound similar, I think these passages are referring to different ways of God speaking.
In 1 Kings, Elijah is depressed and he feels that he is the only person left who still serves God. God teaches Elijah that sometimes God’s voice is heard in a gentle whisper, just as his people are sometimes not so bold and obvious. There were in fact 7000 worshippers of God in Israel, but Elijah hadn’t recognized or noticed them. In this case, the whisper of God was a special event sent to teach a specific lesson. It doesn’t appear that God has spoken to anyone else in exactly this way again.
Isaiah seems to promise God’s guidance in a more general way. However, I don’t think Isaiah is necessarily referring to an audible voice. Rather, if we ask God for help he will guide us as surely as if someone was giving us instructions. How this works in practice will depend on the circumstances. Sometimes it may be through our conscience, or it may be through providence, or through the advice of close friends.
Occasionally, God has spoken audibly. For example, Samuel heard God speaking to him when he was a young boy (1 Samuel 3). But there is no suggestion in scripture that all believers in all ages will hear his voice in this way.