The Reagan administration yesterday issued its version of rules extending protections against on-the-job noise to 2.3 million more workers on high-noise job sites like saw mills, oil fields, textile mills and shipyards.

The announcement by Occupational Safety and Health Administration officials said the new rule, which takes effect tomorrow, still requires that noise levels be monitored and workers' hearing be tested and protected, while deleting Carter administration provisions telling employers how to comply.

OSHA officials estimate the new rule will cost industry $181.5 million annually, down from the $234.6 million price tag the Reagan administration had put on the original rule.

The Carter administration issued the rule four days before it left office. The standard was among the so-called "midnight regulations" held up when President Reagan took office in January.

In yesterday's announcement, OSHA Administrator Thorne G. Auchter said, "In general, we have used a 'performance approach' in choosing those provisions to put into effect. This means we set forth a strict regulatory goal but . . . permit employers flexibility in how they achieve it."

The regulation does not cover workers in the agricultural and construction industries.

The rule still requires employers to monitor noise levels and give hearing tests and protective devices to workers exposed to an average of 85 decibels of noise or more during an eight-hour shift. (That noise level is roughly what the a person hears when operating a power lawnmower, according to one expert.)

But instead of requiring employers to monitor the noise exposure of a representative worker at a job site, the new rule lets employers decide if they want to monitor a worker or general noise levels in a work area.

It also postponed or relaxed requirements specifying which medical specialists must administer hearing tests to workers, how a significant hearing loss is defined and how much information must be made available to workers about the noise levels at their job sites. The agency is soliciting comments through Sept. 22 on the parts of the rule that were delayed.

OSHA estimates 5.1 million workers at more than 300,000 job sites are exposed to an average of 85 decibels of noise during their workdays. Of these, 2.8 million are exposed to the maximum average limit of 90 decibels and so are covered by existing hearing conservation standards. (Ninety decibels, one expert said, is similar to the noise heard in an open car on a freeway when a tractor-trailer passes.)

Both labor and industry experts had little time to examine the new rule and so were reluctant to comment. Still, industry representatives expressed cautious optimism while one AFL-CIO health expert said the shift in the monitoring requirements could eliminate protection for many workers.

Elsewhere in the Labor Department yesterday, the staff of the Office of Federal Contract Compliance Programs put the finishing touches on a controversial set of rules reducing the scope of job bias rules for companies that do business with the government.

The proposals, cutting back the number of contractors covered by affirmative action rules and relaxing specific requirements, are expected to be published in the Federal Register Tuesday.