In the breathing period permitted by President Reagan's 60-day freeze, a task force of regulatory experts is determining how much leverage the president has to reverse, reopen and redirect the environmental, health and safety regulations that Reagan and his aides say have "shackled" the economy.

The administration's leverage is limited in some cases by specific congressional directives, and in others by political factors. Even so, Reagan's deregulators believe they can have a direct impact on scores of major rulings by executive branch agencies like the Environmental Protection Agency and the Occupational Safety and Health Administration -- two agencies whose economic impact is particularly great.

"I think this administration is thinking big on regulatory reform," said James C. Miller III, executive director of the Cabinet-level Task Force on Regulatory Relief headed by Vice President Bush.

The new administration has not yet filed the top posts at EPA or OSHA, but in Miller it has a student of the bureaucracy who served in the Ford administration and spent the Carter years at the American Enterprise Institute in Washington, developing a strategy for deregulation.

Miller, regulatory administrator at the Office of Management and Budget, and other OMB officials are preparing a new presidential executive order that will make "a significant change in the way agencies issue only those rules that are essential and even then impose the least expensive of the alternatives.

One regulatory issue, of the many that Reagan aides are reviewing, illustrates the potential reach and limits of the new administration's deregulation authority. That is the six-year fight over federal control over noise in industrial plants, where day-long sound levels could threaten the hearing of more than 5 million workers.

OSHA has called for expensive changes in equipment and plant layout in a General Motors plant where noisy, high-speed stamping presses are used to make auto components, But Miller and Thomas F. Walton, manager of regulatory economics for GM, writing in the September 1980 issue of the AEI publication "Regulation," contend that the problem could be solved by requiring workers to wear ear plugs or ear muffs.

The costs of equipping workers with ear protection would be much less expensive than the OSHA plan, which could require construction of an addition to the plant to permit the machines to be spread farther apart and surrounded with sound-deadening enclosures.

OSHA's policy is centered in two regulations: A basic 1974 Noise Exposure Standard requires that when workplace noise exceeds an average of 90 decibels over an eight-hour day (or higher levels for briefer periods), employers must make engineering changes in machinery or reduce the workers' exposure to noise by limiting their time on the job. Only when these controls aren't feasible does the regulation permit companies to use ear muffs and ear plugs to protect workers.

On Jan. 16, in the final week of the Carter administration, OSHA issued a new regulation saying that when the average noise exposure exceeds a lower trigger point of 85 decibels, companies must begin a hearing conservation program, installing noise monitoring equipment to give precise warning when the 90-decibel mark is reached, and establishing testing programs for employes.

According to local sound measurements, a bus accelerating from a curb records 85 to 90 decibels. A boeing 727 jetliner, on takeoff, records 91 decibels when measured one-quarter mile from the side of the runway.

The issue of whether protective equipment should be used instead of the much more costly changes in plant equipment and layout runs throughout OSHA's regulatory calendar, usually pitting companies against unions. Attorneys for the unions have opposed the use of masks, respirators and other personal equipment as permanent protection, noting that they often are uncomfortable, interfering with vision and voice communication. Some do not fit well over safety glasses, for example, nullifying their protection.

In Miller's view, however, an OSHA administrator has the descretion under the law to rule that personal protective devices are acceptable methods of meeting noise control standards and other health and safety standards. And because of the vast economic savings resulting from that least-cost approach, the Task Force would not hestitate to ask the new OSHA administrator to consider taking just such a position, Miller told reporters.

"I'm sure we would precipitate a few lawsuits," Miller said.

Such a shift by OSHA on the noise issue would permit a much wider use of personal equipment by companies safe in the knowledge they were in compliance with federal safety rules. The burden would then fall to unions or other OSHA critics to try to reverse OSHA's rulings by appealing to the independent OSHA Review Commission and, if unsuccessful there, to the federal courts. In the meantime, the companies would be spared the costs of making the more expensive physical changes in their plants.