When you know a person, you can always spot and hear him/her right away, within a loud and crowded room. Hearing God can be like this, too.
Scientists have discovered something called the Cocktail Party Effect. In 2012, doctors used high-resolution brain recordings to see this in action. They placed people in large crowds (parties/lots of multiple conversations taking place simultaneously, music playing and other actions). Two people in the midst of the crowd and noise could maintain a high level of connection, interaction and communication, when both parties were interested and face-to-face! Even Siri can’t do this... ask her a question in the midst of other voices! The study found that common interest and face-to-face communication, allowed people to disengage the noise and distinguish one voice amongst the noise! You are designed to hear God's voice, when you are cultivating your relationship and spending time with Him.
John 10:27 (NKJV) "My sheep hear My voice, and I know them, and they follow Me."