Avenues for constant barking
Constant barking can be a genuine disturbance, and you usually have a few avenues depending on who owns the dog and local rules.
If the dog's owner is another tenant of your landlord, the lease often includes pet rules and rules against disturbing other residents. Reporting the ongoing barking to your landlord in writing can give the landlord grounds to enforce those rules. Keeping a log of when and how long the barking happens makes your complaint stronger.
Many cities and counties also have specific rules about persistent animal noise, sometimes handled through animal control or a local nuisance ordinance. That can be an avenue even when the landlord's authority is limited.
If you feel safe doing so, a calm word with the owner sometimes helps, since they may not realize the dog barks when they are away.
Document the pattern, stay factual, and avoid confrontation that could become tense. If a landlord ignores repeated, documented complaints about a tenant's disruptive dog, 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.