It seems reasonable to me that you don't always have to actually knock on a door in order to give proper knock notice. So when, as here, the police sit in your front yard with their lights flashing, screaming over their car's public address system "Anchorage Police with a warrant for 1502 West 32nd Avenue," for thirty seconds to a minute, that may consistute proper notice in some cases. So Judge Wardlaw seems right that the search here may well have been proper.
Still, would it have hurt to knock? I mean, they banged on the door with a battering ram for 10-12 seconds before they finally smashed it down. How about taking a couple of seconds before smashing the door down -- say, during the minute or so you're screaming at them over your P.A. -- and knock, or ring the doorbell, or even just say something like "Hey, dude, how about letting us in?" Maybe it's not constitutionally required in all cases, but I think it'd be a darn nice thing to do before smashing in someone's door. I'm sure the Founding Fathers would have wanted the British to do it.