An important reason why the breath is used as a meditation object is that it helps us to develop awareness. This kind of meditation is called in Pali anapanasati. It is awareness or mindfulness or attention in relation to the in-breath and the out-breath. A problem meditators have is that they try to exclude other things, they try to exclude sounds, for instance. When they hear sounds they become a problem. When they have thoughts they also hate the thoughts. Poor thoughts!
Any sensations in the body, they think this is a disturbance or a distraction in the meditation. But it is very simple: the first emphasis must be on awareness. Just being aware of whatever is happening. This gives us a very interesting experience: you hear sounds, so you are aware of the sounds, and then see with the sounds what happens to you. We see we can convert sounds into noise, which is then disturbing us. It can be a very deep realisation, that the problem arises because of the way we relate to things.
When I talk about sounds, I sometimes speak about an experience we have in the meditation centre at Nilambe. There is a bell to wake you up at 4:45 in the morning. Thus you can just imagine what association the sound of the bell has! But it is the same sound which is heard to indicate lunch. No difference. Where is the problem? It rests in its meaning, the associations we make. So it is not the sound, not what you hear, but how you relate to it.