Structure-borne sound travels great distances

Principle:

Vibrations in solids can travel great distances before producing airborne sound.  This problem is especially pronounced in concrete buildings and on ships.  When the structure-borne sound reaches a large surface, the airborne sound radiated can become a problem.  The best solution is to block the vibrations as close to the source as possible.

Example

Vibrations and stop/start shocks from an elevator drive are transmitted throughout a building.  Structure-borne sound is carried hundreds of meters in the concrete skeleton, virtually without attenuation.

Control Measure

The elevator drive can be isolated from the building structure by flexible elements.  Further reduction can be achieved by constructing the elevator shaft and installing the drive so that they are completely isolated from the rest of the building structure.

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)