Parakeets use calls for everything -- that means EVERYTHING: comfort, social contact, pleasure, discontent, boredom and most of all, to get your attention. Getting a moment's peace means satisfying all of your highly vocal feathered pal's social needs.
Where You At?
Zoologists speculate social vocalization arose in habitats where it was hard for animals to see each other. Look at the leaf cover in jungles where everything living is loud: screaming insects, chattering monkeys and squawking birds. Jungle birds, such as your parakeet, are second only to primates in their range of vocalizations (including large, hairless primates -- is this getting personal?).
Egging Him On
Natural parakeet (and parrot) behavior features the "contact call." This is an extremely loud chirp, scream or squawk. Its only purpose is to get other birds to squawk back.
In your once-peaceful home, this means if you yell at your noisy bird to shut up, he thinks, "Yay! You're answering me! My flock is here!" and he says, "Squawk, squawk, squawk!"
Screaming at your bird when you're sick of his incessant chirping is one of the most common mistakes parakeet owners make. You couldn't give your noisy companion a more reinforcing reward if you tried.
I'm Bored and Lonely!
Parakeets and parrots are extremely social. They live in flocks of up to several hundred birds in the wild. Their social structures and relationships are very similar to ours and the most rewarding activity in their lives is interacting with other birds.
So what happens when we put them in a cage in our homes, alone?
To put it bluntly, unless you can replace all their natural social interactions, you're following a recipe for an unhappy, lonely, crazy bird. Parakeet chirps are their language, and your pet is probably spending a great deal of his time calling out to you for comfort and contact. A daily routine of play, training, talking to, handling, treats and out-of-the-cage time isn't a luxury, it's a necessity for a happy bird and quiet home.
A great reminder is, "If you meet the need, the need goes away." The more time you spend actively talking to and handling your bird, the quieter he will be when you can't pay attention to him.
Parakeets are not the human-language talkers their larger parrot cousins are, but they are natural mimics. They're intelligent, curious and engaged in their surroundings. They'll try to copy whistles, music, telephones, squeaky doors and noises from humans and other pets.
Your feathered friend's environment is greatly enriched by adding noise, including talking and music. Making these a part of his day when you won't mind his chirping (such as while you're at work, preparing a meal or hanging out with your partner or friends) will give him an appropriate outlet, which means that he'll be quieter when his incessant chirping is distinctly not welcome (such as when you're trying to sleep).