Your records are the evidence
Proving a noise problem is about showing a clear, ongoing pattern and that the landlord knew about it — since noise leaves no physical damage, your records are the evidence.
The foundation is a detailed noise log: each incident's date, start and end time, duration, what the noise was, and how it affected you. A long, consistent record is far more convincing than memory or a single complaint. Add time-stamped audio or video recordings when you can capture them.
Keep every written complaint to the landlord and any responses, since these show the landlord had notice and whether they acted. If police or code enforcement responded, note the dates and any report numbers, and keep copies of any citations. Statements from other neighbors bothered by the same noise can corroborate your account.
Organize everything by date so the pattern and the landlord's inaction are clear. This kind of record supports you whether you are pressing the landlord to enforce the lease or pursuing a claim. If you want help understanding what your documentation shows, a free, confidential review can walk you through it.
This is general information about California tenant rights, not legal advice. Every situation is different.