I own 5 dogs, they're all over 4 years old, the oldest being 7. Anytime a stranger come into our property and they notice, or there's a noise that they don't like, they bark at it. We want them to still be protective when someone is on our territory (they're a great alarm system, lol), but how can we get them to be quiet on command. Obviously we've had them all a long time, and I've tried training by the books with treats and scolding. All I get from anyone of them is a response of "LOOK FOOD, EVERYONE BARK" and scolding only affects them for a few minutes. They're like rebellious children! I love 'em but they just don't know how to be quiet on command (what so ever). And getting them their food is a barking frenzy as well! I know they're all quite old to be trained but I never thought to you Yahoo! Answers till now. Your help is greatly appreciated.
Older dogs / parents: male (About 7 years old), female (about 6 years old, not totally sure, we found her on the streets long ago, never found her owners).

Younger dogs / pups: 2 female, 1 male. (All about 3-4 years old)