In 2002 an article was published on auditory performance of persons living in remote parts of the PR China. The study was performed in cooperation with the ENT Department of FMM university in Xian. Most of the persons examined were not exposed to technical noise, but a few of them had to endure extreme levels of noise, over a long time. Contrary to common assumptions, it could not be confirmed that persons not exposed to technical noise are hearing better than persons living in loud cities. Furthermore, it was apparent that acute acoustic trauma was wide spread, caused by fire crackers and other devices resulting in powerful impulses. The equal-energy-concept that is the basis for auditory protection does not explain these findings.
You can download the full article here: Fleischer-2002-TheIntelligentEar.pdf (2.2 MB)