Understanding why roosters crow might help you tolerate your cockerel's cry, but it won't make it any quieter. While you won't be able to quiet the cacophony completely without surgical intervention, reducing the sexual, territorial and protective triggers from your roo's life can make life in the chicken yard quite a bit quieter.
Divide and Conquer
A rooster's daily routine revolves a great deal around mating and protecting his harem of hens. Morning's first light often highlights roosters perched on a high area proclaiming their dominance and claiming their territory. Back-and-forth crowing between roosters let each other know where the boundaries are and whose hens are in the area. You can eliminate this back-and-forth crowing by keeping only one rooster on your property so there are no territorial disputes.
A Solitary Life
A rooster will keep in touch with his flock of hens throughout the day, crowing to them to call them to food he's found, to alert them to danger or signal them to the roost at night. A pet rooster kept out of sight and scent of hens naturally will find less reason to crow. A rooster kept alone seldom finds reason to crow unless he's low on food or bored. Give him an area to forage for bugs and fresh greens and plenty of fresh water to enjoy more of the sound of silence. If chicks are what you're after, you can put a hen in with him temporarily to produce fertile eggs.
Tuck Him in for the Night
Some roosters' internal clock have them crowing long before the sun comes up. A passing car or bright street light may elicit sleep-shattering crows long before the crack of dawn. Putting the rooster in a darkened cage each night eliminates any triggers to crowing in the night. Simply pluck your rooster off the roost when he has turned in for the night and deposit him in a well-ventilated cage covered with a dark cloth. Putting the cage in a darkened garage or shed adds an extra layer of darkness, but be sure the shed will not get too cold or hot for him before you retrieve him in the morning. His circadian rhythm will kick in despite the darkness as the day becomes bright, eliminating the possibility that you'll forget about him.
No More Crow
Two types of surgery can stop the rooster's crow. Surgical castration renders him a capon, and his reduced hormones and sexual urges will diminish his urge to crow. Surgical decrowing provides a quicker fix to the noise problem, with a 75 to 85 percent success rate. The veterinarian makes a small incision on either side of the rooster's syrinx -- where the crow originates -- diverting the air into the clavicular air sac. When the rooster tries to crow, you'll usually only hear a hiss or raspy sound. Not all veterinarians perform the surgeries, and cost can be prohibitive.