Exactly. The lack of consistence can be off-putting.Sound overall needs a little bit of work. It can get obnoxious when you're in the attic of a building and you hear every single zombie in the vicinity.
Sometimes you hear them hissing and groaning right into your ear, even though they are in the next building... all of sudden they become ninjas and sneak up on you in complete silence - no moaning, no footsteps, no floor creaking, nada. It doesn't seem to matter if they're walking on gravel, leaves, or a carpet made entirely of squeaky toys.
It's always disconcerting when I'm checking inventory and suddenly, with no warning whatsoever, one of them fat tourists sucker-punches the living bejeezus out of me - and THEN proceeds to belch in my face and make the noises that could have alerted me of its presence in a timely fashion.
Meanwhile, the cricket chirping still drowns out my minibike's engine at full throttle.

I understand none of those problems prevents me from playing the game (750+ hours and counting).
I also understand the audio might not be high on the priority list, but I do think its current state is detrimental to the overall experience, and talking about it helps to put the issue in perspective.