There are many variables. Even people who think they hear "every" gun shot, probably don't, but they are more hypervigilant when it comes to gunfire than the average person so they notice it more, while other people can tune out a lot of background noise but be extremely tuned in to sounds that are important to them, whether these be pager beeps, baby monitors or something else. I'm in a very rural neighbourhood, not that far from the area in question, and there's a lot of noise from the (very busy) road, though it gets quiet at night for the most part. Still, most people around here get used to loud bangs of blowouts, trucks backfiring or dropping/dragging something, and other sharp, loud, anomalous sounds.
I hear gunfire on a regular basis, usually after dusk, and always coming from back in the bush or swamp. People have set up their own target shooting ranges etc., probably a bylaw violation (especially at night) but not criminal. Dogs can however get used to the sound. Not long ago I had a near neighbour (a renter, since moved) who let a posse of his friends come over and shoot rifles on the back lot, maybe 300 m from my property line. At first my dogs were pretty freaked out, but within a few weeks they totally ignored it. Fireworks, though, like on Victoria Day, are a different story. Dogs hate those (probably smell the stuff too).
Another neighbour who lives nearby says he hasn't heard the gunfire, either at night or during the day, or if he did, he didn't notice. Since the tenant with the rifle-toting buddies moved away, I haven't heard any from that direction, and only occasionally from the swamp. So the frequency of guns being fired in the country probably has a natural ebb and flow by location, population and time. Some years you get a lot, others none, and some people (and dogs) are more tuned into it than others.
AFAIK Bullmann wasn't asked on the stand about whether he regularly heard gunfire in the area, but likely he could have heard the sounds of the gun club on Alberton Road (I've heard it), and someone pointed out a silencer could have been used though it would likely have had to be smuggled into Canada by D the F. You can only draw very limited conclusions from what people didn't see or hear, though, because of the well-documented existence of inattentional blindness, which I posted about before, that means we tend not to notice even very important things happening around us if our attention is on something else.
