Noise is therefore a common occupational hazard in a large number of workplaces such as the iron and steel industry, foundries, saw mills, textile mills, airports and aircraft maintenance shops, crushing mills, among many others. In many countries, noise-induced hearing loss is one of the most prevalent occupational diseases. According to a Environmental Protection Agency (EPA)/USA report in 1981, there are more than nine million Americans exposed to a daily average occupational noise level above 85 dB(A); this number has increased to about 30 million in 1990. Most of these workers are in the production and manufacturing industries (see Table 5.1). Studies in Germany and other industrialized countries have shown that the proportion of those exposed to daily average noise levels above 85 dB(A) can generally be taken as 12 % to 15% of all employed persons; that is 4 to 5 million persons in Germany (Pfeiffer 1992). After many years of exposure to noise, there are numerous cases of occupationally related hearing damage recognized