FOREWORD

In recent years noise has had an increasing influence on users of machines. Exposure to excessive noise levels may cause permanent hearing damage and, also, affect peopleapos;s efficiency, moods, temperament and comfort. Local, State and Federal Governments have enacted legislation to control noise level exposure.

Due to the recent emphasis on health and safety considerations, a large number of people with no special training in sound have had noise control problems thrust upon them. This booklet provides a method of predicting approximate sound pressure levels in industrial and commercial areas.

The method is intended for estimating sound pressure levels and should not be construed as a guarantee of results. It requires a knowledge of the sound levels, location of all sound sources, and room characteristics. Throughout this booklet, for simplicity, emphasis is placed on the use of overall dBA. A more detailed analysis can be obtained by using the same method for each octave band sound level as shown in the appendix.

Machine sound level data are normaly expressed as single dBA levels or in full octave band dB levles, unweighted, in terms of sound pressure or sound power.*

An example is included to assist the reader in understanding the method described in this publication. Instructions for calculation  and corresponding sample calculations are presented in a parallel fashion for convenient cross reference.

*The NEMA Standards Publication for Motors and Generators, MG 1, has for a number of year included sound levels for Design A, B and C alternating-current squirrelcage induction motors, 1 through 250 horsepower, in terms of sound power levels as measured in accordance with the IEEE Test Procedure for Airborne Sound Measurements on Rotating Electric Machinery, Publacation No. 85.

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