Matthew 11:15 He that hath ears to hear, let him hear.
Two types of ears:
With our physical ears we hear certain ranges of sound but with the spiritual ear we hear the voice of God. Jesus said about some, hearing they hear not neither do they understand . . .but blessed are your ears for they hear. We don’t hear God in an audible voice (it has happened but is the exception not the norm) but with our spiritual ears through the Spirit dwelling within us 1 Corinthians 2:10-11 But God hath revealed them unto us by his Spirit: for the Spirit searcheth all things, yea, the deep things of God.
11 For what man knoweth the things of a man, save the spirit of man which is in him? even so the things of God knoweth no man, but the Spirit of God.
When God called Samuel Samuel thought that it was Eli calling him. It may be that God used a voice that sounded like Eli so Samuel just assumed that there was no one else arou8nd it had to be Eli. Either way God used men and women to speak His words to others