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MIL-T-62531(AT)
APPENDIX A
Verification Rationale
The effectiveness of safety provisions shall be determined during first article testing.
Verification Guidance
Recommended changes to correct any safety related hazard discovered during testing should
be reported to the contracting officer.
Verification Lessons Learned
3.14.1 Noise. The vehicle shall comply with both the exterior and interior noise limits
specified herein. Exterior noise - The vehicle shall comply with the exterior noise requirement
as specified in MIL-STD-1474. Interior noise - The steady state noise levels in personnel
occupied areas shall be below 85db(A) when measured for maximum noise as specified in
MIL-STD-1474. The personnel occupied areas shall be each operator or crew positions.
Rationale
MIL-STD-1474 establishes noise limits for Army materiel and prescribes the testing
requirements and measurement techniques for determining conformance to the noise limits. The
standard is intended to reduce hearing loss among personnel exposed to noise caused by Army
materiel, improve speech communications in the noise environment and, when appropriate,
decrease possibility of aural (hearing) detection of Army materiel by the enemy. This standard is
also intended to cover typical operational conditions and is applicable to design of all new
systems, subsystems, equipment and facilities which emit acoustic noise to personnel areas.
Guidance
The problem of noise within closed vehicles became serious with the introduction of new
construction methods, new materials, and high vehicle speeds. It usually arises from the
vibration of surfaces in contact with air. Body or hull panels may be major source of noise in
thin-skinned vehicles. Noise with the vehicle interferes with communication: and if the sound
levels are high enough and continuous, the efficiency of the personnel is adversely affected. As
in temperature and humidity considerations, there are physiological and physiological boundries
to noise tolerance. The reaction to a range of noise varies from physical discomfort to actual
physiological damage. Pain and illness may result from exposure to noise. The amount of noise
that can be tolerated by the average person depends on several factors. The sound pressure level,
the frequency, and the duration of the noise are some of the factors which determine the reaction
to various sounds. In general, shrill, high-pitched, irregular sounds are judged less pleasant than
low-pitched, regular sounds.
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