Im thinking of a new can, is it the case that larger = less noise ?

Generally yes.
But even a humungous one will need some silencing properties

As a general rule it is an exponential curve, a jump from 4 inch to 5 inch has a large effect, 5inch to 6 inch less and so on. We use 6 inch straight through silencers but in order to get them quiet enough we use a stitched woven blanket instead of wadding. The results are fairly dramatic in terms of silencing
best regards
Andy

cheers for the info