Prayers can be answered with an audible voice. The prophet Samuel was called four times with a voice that awakened him from sleep (1 Sam 3:4-10). It would be great if every prayer was answered with an audible voice from the heavens, but this is an exception. At first glance, one would probably think that Enos heard an audible voice. However, verse 10 explains that the voice came into his mind again, implying that the first voice was heard not with his ears but with his heart and mind. This is a much more common way to have the Spirit communicate with your soul—in an inaudible, but no less clear, manner. Nephi expressed the following, he hath spoken unto you in a still small voice, but ye were past feeling, that ye could not feel his words (1 Nephi 17:45, italics added). This same concept is eloquently expressed by the Prophet Joseph Smith, who said:
"A person may profit by noticing the first intimation of the spirit of revelation; for instance, when you feel pure intelligence flowing into you, it may give you sudden strokes of ideas, so that by noticing it, you may find it fulfilled the same day or soon; (i.e.,) those things that were presented unto your minds by the Spirit of God, will come to pass; and thus by learning the Spirit of God and understanding it, you may grow into the principle of revelation, until you become perfect in Christ Jesus." (Teachings of the Prophet Joseph Smith, p. 151)
Boyd K. Packer
"Enos, who was 'struggling in the spirit,' said, 'Behold, the voice of the Lord came into my mind" (Enos 1:10; emphasis added). While this spiritual communication comes into the mind, it comes more as a feeling, an impression, than simply as a thought. Unless you have experienced it, it is very difficult to describe that delicate process." (The Things of the Spirit, pp. 89-90)
Boyd K. Packer
"We do not have the words (even the scriptures do not have words) which perfectly describe the Spirit…The scriptures usually use the word voice, which does not exactly fit. These delicate, refined spiritual communications are not seen with our eyes nor heard with our ears.… It is a voice that one feels more than one hears.
"…I have come to know that inspiration comes more as a feeling than as a sound…Ponder and pray quietly and persistently.… The answer may not come as a lightning bolt. It may come as a little inspiration here and a little there, 'line upon line, precept upon precept' (D&C 98:12). Some answers will come from reading the scriptures, some from hearing speakers. And, occasionally, when it is important, some will come by very direct and powerful inspiration. The promptings will be clear and unmistakable." (Boyd K. Packer: Watchman on the Tower, by Lucile C. Tate, p. 279)