Introduction
Noise is one of the most pervasive and important physical
hazards at workplaces.[1] Millions of workers worldwide
are exposed to work-place noise.[2] According to National
Institute on Occupational Safety and Health (NIOSH),
14% of working population in the US is exposed to
noise higher than 90 dBA in the workplace and this ratio
exceeds 25% in such manufacturing plants and industries
such as textile, transportation, lumber and wood, and food
and kindred.[3,4] Thus noise-induced hearing loss (NIHL),
by early exclusion of skilful and experienced workers
from production cycle and high costs of treatment,
rehabilitation and compensation, can impose a large social
and economic burden on the society.[5,6] Likewise, NIHL
can affect the workers` quality of life and cause problems
such as social isolation, depression and an increased risk of
accidents.[7,8] One important issue is that NIHL is frequent,
permanent and irreversible, but preventable.[9]