Among people aged 20–29, 19.2% had an audiometric notch, compared to 27.3% of people aged 50–59. Males in general had a notch more often than females, regardless of occupational noise exposure, for both unilateral and bilateral audiometric notches. An epidemiological study of 6557 automotive manufacturing workers in China (median age 28 years old) reported that in 62% of the settings where noise exposures were evaluated, levels exceeded the recommended level of 85 dBA. The prevalence of hearing loss was 41% among auto part manufacturing workers, followed by 31% of power train workers and 24% in automotive manufacturing. Across job categories, the highest prevalence rate was observed among welders, of 53%. The prevalence rates were associated with noise levels and the workers cumulative noise exposure. Occupational noise exposure is the main risk factor for work-related hearing loss. One study examined hearing test results obtained between 2000 and 2008 for workers ages 18–65 who had a higher occupational noise exposure than the average worker. Of the sample taken, 18% of the workers had hearing loss. Of the occupations considered, the Mining industry had the highest prevalence and risk of hearing loss, at approximately 27%. Other industries with a higher prevalence and risk included Construction (23.48%) and Manufacturing, especially Wood Product and Non-metallic Mineral Product (19.89%), Apparel (20.18%), and Machinery (21.51%). Estimates of rates of hearing loss have been reported for workers in the Agriculture, Forestry, Fishing, and Hunting (AFFH)  sector.
As harmful noise exposure continues, the commonly affected frequencies will broaden to lower frequencies and worsen in severity. Prevention
NIHL can be prevented through the use of simple, widely available, and economical tools. This includes but is not limited to personal noise reduction through the use of ear protection (i.e. earplugs and earmuffs), education, and hearing conservation programs. For the average person, there are three basic things that one can do to prevent NIHL: turn down the volume on devices, move away from the source of noise, and wear hearing protectors in loud environments.Non-occupational noise exposure is not regulated or governed in the same manner as occupational noise exposure; therefore prevention efforts rely heavily on education awareness campaigns and public policy. The WHO cites that nearly half of those affected by hearing loss could have been prevented through primary prevention efforts such as: "reducing exposure (both occupational and recreational) to loud sounds by raising awareness about the risks; developing and enforcing relevant legislation; and encouraging individuals to use personal protective devices such as earplugs and noise-cancelling earphones and headphones." Personal noise reduction devices
Personal noise reduction devices can be passive, active or a combination. Passive ear protection includes earplugs or earmuffs which can block noise up to a specific frequency. Earplugs and earmuffs can provide the wearer with 10 dB to 40 dB of attenuation. However, use of earplugs is only effective if the users have been educated and use them properly; without proper use, protection falls far below manufacturer ratings.