Stig Ingemansson’s Noise Control: Principles and Practice – A1 Sound Behavior: Causes of Production

Changes in force, pressure, or speed produce noise

Principle:

Sound is always produced by changes in force, pressure, or speed.  Large changes produce loud noises, small changes produce less noise.  In many processes the same result can be achieved with the application of high power for a short time period, or with less power over a longer period.  The former results in high noise levels, while the latter produces much less noise.

Example

In a box-making machine cardboard is cut with a guillotine.  The knife must strike rapidly and with great force for the cut to be perpendicular to the direction of motion.  Much noise results.

Control Measure

Using a knife blade which travels across the production line the cardboard can be scored with minimal force over a longer time period.  Since the cardboard strip is in continuous motion the knife must travel at an angle with the moving production line for the cut to be perpendicular.  The cutting is practically noise-free.

More about this series

The illustrations in this feature article appeared first in a book published in Swedish by Arbetarskyddsfonden, the Swedish Work Environment Fund. The Fund was established by national legislation in Sweden to conduct research and education in the field of work environment improvement, and is jointly operated by Swedish employers and labor unions.

The book was translated into English and disseminated as a guide for workers and employers by the U.S. Department of Labor. It has also been translated into other languages, notably Finnish and Danish, but its overall circulation has been limited.  The illustrations are being republished here to give them wider circulation, particularly among noise control engineers.

The formulation of the principles, the choice of examples and the preparation of preliminary sketches was the work of Stig Ingemansson. The original illustrations were prepared by Claes Folkesson.

The principles are presented in eight sections:

A. Sound behavior (8)

B. Sound from vibrating plates (8)

C. Sound production in air or gases (7)

D. Sound production in flowing liquids (2)

E. Sound propagation indoors (5)

F. Sound propagation in ducts (6)

G. Sound from vibrating machines (6)

H. Sound reduction by enclosure walls (5)