Auditory Hazard Assessment Algorithm for Humans: Difference between revisions

Revision as of 21:22, 22 January 2020

Revision as of 21:29, 22 January 2020

Line 12:

== Operation ==

The AHAAH calculated the auditory hazard of impulse sounds by modelling their transmission based on how it interacted with an electroacoustic model of the [[basilar membrane]] in the [[cochlea]]. This wave motion analysis relied on the [[Wentzel-Kramers-Brillouin approximation|Wentzel-Kramers-Brillouin (WKB) wave dynamics method]], which was normally used to solve wave function problems in [[quantum mechanics]] and [[solid-state physics]] for several decades. The computer program could calculateestimates the acousticmotion hazards fromof the free-field,stapes through hearing protection,footplate and throughuses the middleWKB earapproximation where theto hearingestimate damagebasilar typicallymembrane occurredmotions. The AHAAH represented the output in auditory risk units (ARUs), which related to the damage caused by displacements of the basilar membrane in the inner ear at 23 different locations. According to the model, the recommended limit for daily occupational exposures were 200 ARUs, while any dose greater than 500 ARUs were predicted to produce permanent hearing loss.<ref name=":1" /><ref name=":9">{{Cite journal|last=De Paolis|first=Annalisa|last2=Bikson|first2=Marom|last3=Nelson|first3=Jeremy|last4=de Ru|first4=J. Alexander|last5=Packer|first5=Mark|last6=Cardoso|first6=Luis|date=June 2017|title=Analytical and numerical modeling of the hearing system: Advances towards the assessment of hearing damage|url=https://www.sciencedirect.com/science/article/pii/S0378595516302787?via%3Dihub|journal=Hearing Research|volume=349|pages=111-128|via=ScienceDirect}}</ref>

The AHAAH model consisted of a set of proven algorithms that accounted for a variety of exposure conditions that influenced the risk of a permanent threshold risk, such as noise attenuation caused by hearing protection devices and [[Acoustic reflex|reflexive middle ear muscle (MEM)]] contractions that occur before the onset of the stimulus being received that reduce the damage to the ear in preparation of the sound.<ref name=":8" /><ref name=":10">{{Cite journal|last=Amrein|first=Bruce|last2=Letowski|first2=Tomasz|date=January 2011|title=Predicting and ameliorating the effect of very intense sounds on the ear: The auditory hazard assessment algorithm for humans (AHAAH)|url=https://www.researchgate.net/profile/Tomasz_Letowski5/publication/301511369_Predicting_and_ameliorating_the_effect_of_very_intense_sounds_on_the_ear_The_auditory_hazard_assessment_algorithm_for_humans_AHAAH/links/5716ec1e08aeefeb022c3f3b/Predicting-and-ameliorating-the-effect-of-very-intense-sounds-on-the-ear-The-auditory-hazard-assessment-algorithm-for-humans-AHAAH.pdf|journal=NATO|volume=|pages=|id=RTO-MP-HFM-207|via=}}</ref> Unlike previous energy-based damage models, the AHAAH could also accurately predict the scope of the damage by analyzing the pressure-time dependence of the [[Sound Wave|sound wave]]. Through this method, the model was able to determine why a low level of energy at the [[ear canal]] entrance was much more hazardous than a higher level of energy at the ear canal entrance of an ear protected by [[Earmuffs|ear muffs]]. The model discovered that the former featured a different pressure-time dependence than the latter that was able to more efficiently transfer energy through the middle ear.<ref>{{Cite journal|last=Fedele|first=Paul|last2=Kalb|first2=Joel|date=April 2015|title=Level-Dependent Nonlinear Hearing Protector Model in the Auditory Hazard Assessment Algorithm for Humans|url=https://apps.dtic.mil/docs/citations/ADA622427|journal=Army Research Laboratory|volume=|pages=|id=ARL-TR-7271|via=Defense Technical Information Center}}</ref>