Medicare Part B does not cover routine hearing exams or hearing aids. I got that info from www.medicare.gov.
Social Security Disability Income is just that, income because you are disabled. It is not health insurance.
Medicaid, known as MediCal, in CA, might cover hearing aids, IF you otherwise meet the eligibility criteria for that program. Generally, you have to pretty low income.
Also, if you are in one of those Medicare HMO's in lieu of traditional Medicare, there might be some limited coverage of hearing aids. You would have to talk to the Medicare HMO itself to determine coverage.