Imagine the year is 1980 and this motley crew (see the picture to the right) walks into your office to sell you on some great big scheme that will make everyone a lot of money. Would you listen to them? You might but, even if you did, you probably wouldn't really hear what they said because you would have already discounted them because they looked "different" or "weird."
Of course, the fellow in the lower left-hand corner is Bill Gates and, today, he is the second or third richest person in the world.
If today, a group of young people came into your office with tattoos and pierced noses would you listen to them? To prove that you might not "hear" them, I invited you to watch this 30-second video on the "Mosquito Buzz Tone" — it is a sound that most people over the age of 50 literally can't hear. (If you're over that age you won't be able to hear the sound so invite a younger colleague or a child to watch with you and ask them if they can hear the sound.)
If nothing else this "audio metaphor" should give you pause to consider what else you're not hearing.