Simple steps, solid records
Start with the simplest steps and build a record as you go. Many noise problems can be resolved without a legal fight, but documentation matters if they cannot.
First, if you feel safe doing so, politely let the neighbor know the noise is a problem — sometimes people do not realize how much sound carries. Keep it calm and brief.
Second, if it continues, report it to your landlord or property manager in writing, especially if the neighbor is another of the landlord's tenants. Describe the noise, the dates and times, and how it affects you, and keep a copy.
Third, keep a noise log — dates, times, how long it lasted, and what it was — and save any recordings or messages. This record is powerful if the problem escalates.
Fourth, check local noise rules; many cities have quiet hours, and police can sometimes respond to serious late-night disturbances.
If a landlord ignores repeated complaints about a tenant who keeps violating the lease, a free, confidential review can help you understand your next steps.
This is general information about California tenant rights, not legal advice. Every situation is different.