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The first military standard ([[United States Military Standard|MIL-STD]]) on sound was published in 1984 and underwent revision in 1997 to become MIL-STD-1474D. In 2015, this evolved to become MIL-STD-1474E which, as of 2018, remains to be the guidelines for United States’ military defense weaponry development and usage. In this standard, the [[United States Department of Defense]] established guidelines for steady state noise, impulse noise, aural non-detectability, aircraft and aerial systems, and shipboard noise. Unless marked with warning signage, steady state and impulse noises are not to exceed 85 [[Decibel|decibels]] A-weighted (dBA) and, if wearing protection, 140 decibels (dBP) respectively.<ref name="Amrein" />
The AHAAH’s improvements in accuracy are often attributed to its sensitivity to the flexing of the middle ear muscle (MEM) and [[Annular ligament of stapes|annular ligament of the stapes]]. When someone is forewarned of a sound, the MEM flexes, which is associated with reduced ability of the sound waves to reverberate. When an impulse sound is produced, the stapes’s annular ligament flexes and strongly clips the sound’s
As the MIL-STD-1474 has evolved, technology and methods have improved the AHAAH model’s accuracy. AHAAH has been proven to be more accurate in cases of double protection but not always in unwarned impulse noise instances relative to the competitive metric LAeq8hr.<ref name="Nakashima 2015">{{cite web |last1=Nakashima |first1=Ann |title=A comparison of metrics for impulse noise exposure |url=http://cradpdf.drdc-rddc.gc.ca/PDFS/unc206/p802859_A1b.pdf |publisher=Defence Research and Development Canada |access-date=3 July 2018 |date=November 2015}}</ref> Some suggestions for further development focus on creating a more user-friendly software, the placement of the microphone in data collection, the absence of the MEM reflex in populations, and the reevaluation of free-field conditions in calculations. Agencies such as NATO, the American Institute of Biological Sciences, and the [[National Institute for Occupational Safety and Health]] agreed that these suggestions be attended to before the metric is implemented. This shared conclusion was made prior to the development of MIL-STD-1474E.<ref name="Nakashima 2015" />
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