An appellate court yesterday overturned a federal standard to protect workers' hearing, one of the few health standards promulgated by the Occupational Safety and Health Administration under President Reagan.

In a split decision, a three-judge panel of the 4th U.S. Circuit Court of Appeals in Richmond said, in effect, that the standard was too strict. The decision surprised OSHA officials and labor groups; the latter had accused OSHA of trying to weaken a tough standard that the Carter administration had adopted in its closing days.

The standard, established in 1983, required employers to monitor workplace noise levels and regularly test the hearing of employes exposed to more than 85 decibels of occupational noise, averaged over eight hours. If a hearing loss was found, an employer had to provide workers with hearing protection and reduce their exposure to noise. The standard did not apply to construction or agricultural workers.

"A standard is invalid if it requires an employer to take actions in regard to hazards existing outside the workplace," the two-judge majority wrote. "It is clear from the language of the hearing-conservation amendment, as well as the record before this court, that under the amendment, employers may be subject to requirements and penalties may be imposed as a result of non-workplace hazards."

"Airplanes, hunting rifles, loud music and a number of other sources produce noise potentially as damaging as any at the workplace," the court said. "Yet, the amendment makes no distinction between hearing loss caused by workplace sources and loss caused by non-workplace sources."

In a dissent to yesterday's ruling, Judge James Sprouse said the majority failed to note substantial scientific evidence that prompted the agency to establish the regulation. Even if noises outside the workplace contribute to a hearing problem for a worker in a noisy workplace, "that is scant reason to characterize the primary risk factor as non-occupational," Sprouse said.

OSHA spokesman James Foster said the agency would not comment until it had studied the decision in the case, which was brought by the Forging Industry Association.

AFL-CIO health official Peggy Seminario said, "It's often scientifically impossible to prove that health damage was done solely in the workplace. Does this mean that we should not regulate benzene in the workplace because it also is in gasoline and we might not be able to tell which exposure caused cancer?"

The standard was one of several that OSHA suspended and began to rewrite after Reagan took office. Alice Suter, who wrote the original standard, resigned in 1982 over disagreements about the regulation. She accused the Office of Management and Budget and then-OSHA Administrator Thorne G. Auchter of trying to relax the standard to reduce its cost to employers. The OMB denied that it had ordered OSHA to weaken the standard, and Auchter defended it as fair.