THERE ARE MORE THAN 50,000 people in this city, half of them elderly, who have impared hearing. As you might suspect, not all of them automatically need or would benefit from hearing aids. What you may not realize, however, is that many people have been buying hearing aids without the slightest idea of whether they really need such devices. That's because this city has had no local consumer-protection regulations on the sale of hearing aids. If your hearing seemed poor, you could simply walk in off the street to the office of a hearing-aid dealer and walk out with some device that might cost up to $400 - without any professional, reliable medical or audiological consultation.

It should go without saying that this is no way to treat a sensitive medical issue. The absence of regulations has led to instances in which the sales of hearing aids have run the range from questionable to totally groundless. In 1975, for instance, the National Council of Senior Citizens investigated the practices of hearing-aid dealers in the city. Results revealed that three out of 11 hearing tests that dealers did perform led to recommendations of unnecessary hearing aids. Moreover, most of the dealer's test results were inaccurate, showing recordings of greater than actual hearing loss. Six of eight dealers made no recommendations for consultation with a doctor before testing, and on eight of 11 occasions, dealers made no recommendations for such consultation even after administering their tests.

Fortunately, the National Council and other organizations have sought a law to protect consumers. The city council passed a bill last month but - here's a possible catch - it now awaits Mayor Washington's signature. The measure would prohibit the sale of a hearing aid unless a consumer has had an examination by an audiologist and a physician specializing in ear, nose and throat problems and has a written recommendation from them for an aid.

But the hearing-aid dealers are lobbying hard for a veto by the mayor. They are contending, among other things, that the Food and Drug Administration and the Federal Trade Commission have taken adequate steps. But the FDA regulations are far weaker than the provisions of the city council bill. The dealer lobby also contends that the FDA rules would pre-empt the city law, anyway; yet the FDA regulation notes that a stronger local law may still be allowed to stnad.

Responsible hearing-aid dealers in this city should welcome enactment of the local bill. Consumers need this reasonable protection against unnecessary and possibly harmful purchases. Mayor Washington should sign this bill without further delay.