There are two common reactions to noise coming from a neighbor. The first is resignation. You hate the noise, but you do nothing. The second is anger. You lose your temper and call the cops. There are better ways to handle the situation.
Approach the neighbor. Raising a problem with a neighbor is not easy. But it should always be the first step and, if done with respect and sensitivity, may be the last. Often the neighbor is unaware of a problem -- for instance, the dog barks only when nobody is home. Assume that the neighbor doesn't know and would like to be told.
Warn the neighbor. If complaining doesn't work, get a copy of your local noise ordinance as explained above. Send a copy to the neighbor with a note repeating your request to keep the noise down and explaining that you'll be forced to notify the authorities if you don't get results. Be sure to provide details on the problem, including the dates and times of the noise.
If you rent or live in a planned development, send a copy of the lease agreement or special rules (usually called Covenants, Conditions, and Restrictions) to the neighbor. If that doesn't work, report the problem to the landlord or homeowners' association in writing. Especially if several tenants complain at the same time, the landlord will probably order the tenant to quiet down or face eviction.
Suggest mediation. If you value the neighbor relationship at all, or just want peace in the future, give mediation a try. You and the neighbor can sit down together with an impartial mediator and resolve your own problems. Mediation services are available in most cities and often they are free. Simply call the mediation center, and it will then contact the neighbor for you. For more information, see the Lawsuit, Mediation & Arbitration section of Nolo's website.
Call the police. Still no response from the neighbor? Stereo turned up another notch? Now is the time to bring in the police (or, if the problem is a barking dog, the Animal Control Department). If you have tried to solve the problem yourself, the police will know your complaint is serious and that you need help.
Try to notify the police while the noise is continuing, so they can measure the noise or hear it for themselves. (Some people simply hold the phone out the window.) Sometimes cities won't act until the noise affects two or more persons, to prevent complaints from excessively sensitive people.
Sue for nuisance. As a last resort, you can sue in small claims court. It's easy and inexpensive, and you don't need a lawyer.