6. NOISE CONSIDERATIONS.
Noise Sources. The primary source of noise in hyperbaric chambers
is usually gas flow in pipes. Occasionally the blower for gas circulation in
the atmosphere control loops are noise contributors. Also, care must be
exercised when selecting electric motors for pumps, blowers, or other
required service, because some motors have objectional noise characteristics
when connected to a chamber or piping system. Quantitative information
describing ambient noise in the diving environment is almost nonexistent.
(See Reference 21, Summitt, J.K., and Reimers, S.D., Noise: A Hazard to
Divers and Hyperbaric Chamber Personnel.) Based on general experience,
pneumatic noise in manned hyperbaric chambers can cause two types of
problems: (1) a reduction in diver efficiency resulting from fatigue and/or
poor communications, and (2) temporary or permanent partial loss of hearing.
OPNAV Instruction 6260.2 (Reference 22) establishes an occupational noise
guidance for acceptable noise levels in hyperbaric chambers, however, the
current issue of OPNAVINST 6260.2, Hearing Conservation Program, should be
consulted when designing and testing hyperbaric systems. The following
information has been excerpted from OPNAVINST 6260.2, and is applicable to
sound levels in the hyperbaric environment.
"(1) The analysis of a noise environment and its hazard potential
is a complex task which is highly constrained by the nature of the particular
activity and is subject to revisions imposed by facility updating and
equipment changes. Assessment of the potential hazard of noise exposure
shall be performed by an industrial hygienist.
(2) In the absence of an industrial hygienist assessment to the
contrary, personnel exposed to noise levels of 85 dBa or greater or 140 dB
peak sound pressure level for impact or impulse noise should be considered at
risk, and shall be identified for hearing testing. The noise shall be
considered as potentially hazardous and appropriate measures to control the
exposure shall be instituted.
(3) It shall be mandatory for all personnel exposed to high level
noise associated with gunfire, artillery, or missile firing to wear hearing
protective devices regardless of length of exposure, or the technical/
engineering controls in effect.
(4) No individual shall be exposed for any period of time to
steady state or interrupted steady state sound levels exceeding 115 dBa or to
impulse or impact noise which exceeds 140 dB peak sound pressure level
without the use of hearing protective devices. Occupational noise exposures
which exceed these limits should be controlled by the most feasible
technological/engineering methodology and administrative controls. The use
an individual's exposure while engineering efforts are being pursued. Such
devices shall be used as a matter of routine in those areas/situations where
it has been demonstrated that engineering controls are not feasible.
Labeling of Hazardous Noise Areas and Equipment. Navy work areas
or equipment which produce sound pressure levels of 85 dBa or greater or 140
dB peak sound pressure level shall be appropriately labeled, NAVMED 6260.2.