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→Acoustical Isolation
Decoupling is achieved by using viscoelastic dampers between surfaces, and air gaps to prevent direct conduction. Air gaps need especial attention because they can resonate, especially at the lower frequency (1000-400 Hz) wavelengths of 13.5 to 33.76 in (34.3-85.75 cm). Resonance will transfer energy across the gap.
=== An Example ===
These techniques are applied in the following hypothetical example where a saloon is located above an engine room, and cabins are adjacent to engine-room bulkheads.
Design an engine room entrance that has a double door. The inside door should be the watertight one (with a view port), and the outside one should be air tight. The space in-between would make a good place to hang ear protectors, etc. Both doors should have significant solid mass.
== Some cautions ==
Finally, some cautions. Some complex isolation schemes were described above, but you should keep the design as simple and robust as possible. For example:
* A triple mass-panel sandwich alone that consists of a mass panel glued (viscoelastic) to either side of a bulkhead can achieve attenuations of 60 dB.<ref>ibid</ref>
* Test (sound meters with a range of 35-130 dB can be rented.):
** Start with a basic installation of isolation in the engine room. Run the engine and use a sound meter to measure the noise in adjacent cabin areas. Upgrade the isolation to reach your sound goal.** Or, build a small test box with a logging sound meter inside. Add test isolation externally. Evaluate the performance of your choices by suspending the test box in the engine room and running the engine.
[[Category:Hull]]
