It comes down to control
Sometimes, but not always. A landlord's responsibility for a noisy neighbor usually depends on how much control the landlord has over that neighbor and the situation.
A landlord generally has the most responsibility when the noisy neighbor is another one of the landlord's tenants who is breaking the lease — for example, violating a rule against excessive noise or disturbances. In that case, the landlord often has the power, and sometimes the duty, to enforce the lease and address the problem.
A landlord usually has little or no responsibility for noise coming from people they do not control — such as a neighbor in a building they do not own, street noise, or a nearby business. A landlord cannot enforce rules against someone who is not their tenant.
So the key questions are: who is making the noise, and does the landlord have authority over them? If your noisy neighbor is another tenant of the same landlord and the landlord ignores repeated serious complaints, you may have options. A free, confidential review can help you understand where your landlord's responsibility begins and ends.
This is general information about California tenant rights, not legal advice. Every situation is different.