Attention is proposed to be essential for knowledge. The ability to focus our minds on a specific aspect of our environment enables us to select information among the noise and to process it. Attention compels our brains to ignore all other stimuli and limit our consciousness to the object of our attention. This model explains how we can read a book on a bus, for instance, and ignore the surrounding places and people. If one's attention is focused on the book, he will hear neither the person who addresses him nor the announcement of the next stop.
Attention is not limited to the auditory senses; vision is also affected. Everyone has experienced it: when you are focused on computer work, you fail to notice the Outlook popup that announces a new email, whereas if your attention is not completely dedicated to the work, you are constantly disturbed.