No abstract

No abstract

Sound measuz:ements were conducted In the CH-47B (Chinook) Helicopter under conditions of normal cruise, maximum continuous power, level M t at various air speeds, hover, level acceleration and deceleration, and partial-" ower descent. Results are presented and compared with applicable parts of Miitary Specification MIL-A-8806A and U. S. Army Human Engineering Laboratories Standard S-1-638. Variations of the noise from that specified in these documents are discussed, and it is recommended that the noise be reduced to conform to the specified levels.

In most industrial activity, employee work routines vary from one day to another or from week to week. The United States Occupational Safety and Health Administration (OSHA), recognizing this fact, has specified that an employee's long-term noise exposure should be expressed as a summation of partial exposures to varying sound levels. A technique has been developed that analyzes employee movement, breaking an average day into a series of locations or activities, each with an associated time duration. Sound level data are then acquired for each location or activity. A computer is then used to calculate the partial exposure, as defined by any criterion, for each location or activity and these are summed to express the overall exposure level for each employee job function. The computer also generates a list of noise control priorities and the minimum amount of noise reduction required at each location to achieve compliance with the selected criterion. Maximum priority is given to the location which, when attenuated, will give most benefit to most employees. Determining these minimum reduction levels is most important, as the cost and feasibility of noise control are directly related to the amount of reduction required.