I wrote it already few time here, the most important and often overlooked skill of every professional music producer is the ability of listening. Human hearing can detect frequencies between 20Hz and 20kHz. As we grow older and also due to prolonged exposure to high sound pressure levels, we often lose the extreme ends overhearing spectrum. SO how your hearing compare to other average person your age? Take this video test and verify how old are your ears. And if you cannot hear the highest frequencies, don't panic: You can always train your ears to hear special nuances and details in the music. It is not all about frequency hearing. Good music producers are able to listen music in more detailed and open way. I remember my college days, where I had a teacher who was deaf in one ear: however, he was able to produce a gorgeous music. And the good news is that everyone can learn to hear this kind of depth of perception in his own music production. Someone calls it the color hearing, because it is like seeing the picture in black/white and then seeing the same picture with oversaturated colors post-processed in photoshop: the difference is huge. All you have to do is to have patience to culture your ear (train your ear regularly every day) to gain the ability to zoom into music and add depth to your listening.
IMPORTANT: Watch this video in 1080p, because resolution settings can affect audio. Don't forget to pick up the headphones.