Should I block out sounds during meditation?

No. Sounds are just as much a part of your experience of the moment as everything else. You do not need to try to mentally block out cars driving past, birdsong, or the other mooing cow in the neighbouring pasture.

If a sound draws your attention away from the breath or another meditation object, simply notice it and return as usual. You can even make sounds themselves the object of your attention and simply observe how they arise and disappear again.