Exactly what you did, i had the impression it was a separate setting (was it ever? can’t remember)
Sounds draws them, big Z in the overmap are to be avoided, but otherwise you’d see only stragglers due to hordes. Stragglers are good for immersion - you are never completely safe.
The (statically spawned) zeds of a city are many, and the sounds of all the havoc draw more, and more and more…
You’d have better chances of you did it silently, or hit & run.
The rationale is that all the noise draws stragglers from outside the town, and the constant spawning is the only way to represent that.
Other people know horde mechanics much better than me (and they are still being worked on) but my impression was that each horde has a max spawn number. When all its zeds are dead, it ceases to exist (otherwise the number slowly gets filled up again)
The fact is that even if you kill a horde (impossible early game), another one can converge to the place if you do lots of noise.
Brute force won’t help, just because you are not powerful enough to apply the huge amounts needed. That’s by design.
If i were you, i’d either use that humvee for a hit&run (raid the local library first), or i’d go raiding at night, verrry carefuly (at night getting surrounded can happen, and even a brute can spoil your night, not to mention boomers and such)
PS. You do play the experimental, right? The stable version’s hordes must be totally outdated.
PS2. Be sure to retreat from strong horde opposition, even if it means abandoning everything. You can always return after a month, but right now (early on) you need to survive.