To control noise exposure it is first necessary to determine noise levels in working areas, and exposure time to noise above 90 decibels (A), and evaluate the extent of the hazard. Noise flow diagrams will help in determining the major noise paths and so aid in choosing control measures. A noise control analysis outline is given which comprises plant planning, substitution, and modification of the noise source, by reducing response of the vibrating surface, reducing area of the vibrating surface, using directionality of source, reducing velocity of the fluid flow, and reducing turbulence. Modifications of the sound wave are also considered. Various means of noise reduction are presented using tables, graphs, and photographs of equipment.
The Industrial Environment - Its Evaluation and Control, NIOSH, Centers for Disease Control, Cincinnati, Ohio, Chapter 37