Law and Legal Rights
There is no one law that covers only Deaf and Hard of Hearing people.
Rather, multiple laws address deafness and hearing loss as a disability,
with some laws being more important than others.
The key laws usually referenced are The Americans with Disabilities
Act (ADA) of 1990, the Television Decoder Circuitry Act and the
Telecommunications Act of 1996 (for captioning), the Individuals with
Disabilities Education Act, and the Rehabilitation Act, with its key sections
(Section 504 and Section 508). There are other sections of the Rehabilitation
Act, but Section 504, which requires access to the programs offered by any
program receiving federal financial assistance, and section 508, which requires information technology developed or used by the federal government to be accessible.
The Americans with Disabilities Act (ADA) of 1990, signed into law by President George W. Bush on July 26, 1990, is the law that gave official legal protections to Deaf and hard of hearing people in employment, at places of public accommodation, public services, and telecommunications. 
"Good communication in all settings is essential in every day life. The Americans with Disabilities Act(ADA) includes specific
language specific language regarding communications access
for deaf and hard of hearing people."
Title III of the ADA
Title III of the ADA covers access to places of public accommodation. Subchapter III - Public Accommodations And Services Operated By Private Entities, Section 12181, Definitions, says that the following examples of private entities are considered public accommodations: (F) a laundromat, dry-cleaner, bank, barber shop, beauty shop, travel service, shoe repair service, funeral parlor, gas station, office of an accountant or lawyer, pharmacy, insurance office, professional office of a health care provider, hospital, or other service establishment;
The same interpretation says that public accommodations must "Furnish auxiliary aids when necessary to ensure effective communication, unless an undue burden or fundamental alteration would result." (substantial impact on the business).
An "auxiliary aid" as defined by the ADA means "qualified interpreters or other effective methods of making aurally delivered materials available to individuals with hearing impairments." Alternative methods means techniques such as writing back and forth on paper, or using computerized means of communication.
The ADA Technical Assistance Manual states that the place of public accommodation, e.g. the doctor's office, gets to make the ultimate decision as to what methodology to use, "as long as the method chosen results in effective communication." There can be disagreement over what constitutes effective communication. The Technical Assistance Manual states:
The physician must be given an opportunity to consult with the patient and make
an independent assessment of what type of auxiliary aid, if any, is necessary to
ensure effective communication. If the patient believes that the physician's
decision will not lead to effective communication, then the patient may challenge
that decision under Title III by initiating litigation or filing a complaint with the
Department of Justice.
The National Association of the Deaf (NAD) has a fact sheet online that tells deaf people to notify health care providers in advance of appointments, that they need an interpreter. In addition, it states that the health care provider must pay for the interpreter even if the cost of the interpreter is higher than the cost of the visit. A related NAD fact sheet, Questions and Answers for Health Care Providers, has other important information such as the fact that the cost of an interpreter to the doctor can be covered by a tax credit.