CHAPTER 10.
COMMUNICATION SYSTEMS
1.
SCOPE. Good communications in hyperbaric facilities are important both
for effective use of the chamber and for operational safety. Too often
communications are treated as an add-on feature, resulting in significant
personnel inconvenience and lost time. It is thus desirable for the chamber
designer to consider communications throughout the design process as an
integral part of the chamber system. This chapter discusses audio
communications in terms of the special conditions and problems inherent in
hyperbaric chambers.
Section 1.
AUDIO COMMUNICATIONS
1.
AUDIO COMMUNICATIONS. Continuous voice communications with chamber
crews is essential for both convenience and safety. Factors to be considered
include chamber acoustics, audio system power requirements, pressure effects
on equipment, penetration requirements, and overall layout. The layout of
the communication system shall give primary consideration to the complexity
and intended use of the chamber. For example, a recompression chamber
requires a good two-way communication system from outside control to both the
inner and outer chambers. A saturation complex will require: (1) an open
circuit system in each chamber monitored topside with the other side of the
open circuit system providing topside control and general commands to all
chambers, (2) at least one (preferably two) closed circuit communications
intercom systems from all chambers to topside control. This system will
provide also a round robin network between divers and topside, (3) divers in
the water should have separate communication links topside and to the tender,
in addition to the round robin capability, (4) there should be an in-water
open circuit one-way transducer for topside communications to the divers.
2.
CHAMBER ACOUSTICS. Because of the small size of most hyperbaric
chambers, very little power is required to achieve adequate sound levels.
However, the chamber environment presents a number of acoustic problems,
including echoes, resonances, and helium speech distortion.
a.
Reverberation. Reverberation may be reduced by installing acoustic
baffeling panels against the inner hull. These acoustic baffeling panels are
commercially available in stainless steel which may be painted to increase
light levels within the chamber. To obtain the most effective results, the
panels should be installed 1/2 inch from the chamber walls.
b.
Resonances.
(1) Problem. Any closed space will have a series of
resonant frequencies which tend to be amplified when vibrations of
the trapped atmosphere are excited. The effects are usually not
troublesome in large volumes, that is, ordinary rooms. In confined
spaces with atmospheres of high density, however, the chance
excitation of acoustic resonances by machinery vibrations or other
sources becomes annoying. Since most chambers are cylindrical, they
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