Intense Sound in Submarines,
TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS
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The intensity of the sound produced in air inside an interior space of a submarine by an exterior source is controlled by two principal factors 1. the absorption of airborne sound energy by the interior surface of the walls, by interior furnishings, and by personnel, 2. the transmissibility of the walls separating the interior space from the source. The sound field within an enclosed space for all frequencies having wavelengths less than twice the greatest horizontal, vertical, or diagonal dimension of the space consists of a highly complex system of standing waves. Since half a wavelength of airborne sound even at the comparatively low frequency of 100 Hz is only about 5.5 ft, it is apparent that for most sounds almost any habitable space is many half wavelengths in greatest dimension. If there is no sound absorption within the space and no sound leaks out of the space, a system of standing waves, once established, will exist forever. If the absorption is not zero, but is very low, only a very small amount of energy, equal to the energy absorbed, needs to be added to the system of standing waves to sustain its intensity. Adding even a small amount of additional energy can cause the intensity to increase drastically. Consequently, the existence of high intensity sound in an enclosed space does not necessarily indicate that a large amount of energy is being transmitted into the space.
- Submarine Engineering