A trained musician can hear a chord played and recognize the individual notes. They can hear a "C" for instance. It is rare to be born with "Perfect Pitch", the ability to identify the frequency or musical name of a specific tone, so it must be learned.
This came to mind when I was reading "In the School of the Holy Spirit" by Fr. Jaques Philippe of the Community of the Beatitudes. The Book explains how to hear the voice of the Holy Spirit and be obedient to the will of God.
When we become intimate with the Holy Spirit, and learn to recognize His voice, it is recognized in the noise of life. It takes time and practice to train our hearts to discern the vibration of the Spirit.
I recommend picking up this little book if you want more details on how to listen.