Have you ever experienced difficulty in hearing after a night at a concert? Have you had an exposure to a sudden loud noise that caused reduced hearing in one or both ears for any period of time? How about a buzzing or ringing in your ears after noise exposure? If any of those rings a bell (which you may or may not be able to hear), you may be experiencing Noise Induced Hearing Loss (NIHL). In fact, about fifteen percent of Americans between twenty and seventy may have hearing loss from exposure to noise at work or in leisure activities according to the National Institute of Deafness, https://www.nidcd.nih.gov/.
There is not one simple situation that causes NIHL. The damage to hearing after loud noise exposures may not be immediately apparent. Commonly it is a subtle, progressive damage caused by repeated exposure to loud noises, many times from varying sources over years. The individual may not even be aware until family members or friends point out the concern. The repeated damage from loud noise even from short exposures over time may progress to permanent loss. It is important to wear hearing protection when you anticipate such exposures.
Excessive noise exposure in the workplace is readily recognized as a potential hazard for as many as 30 million Americans. Employers are required by law to evaluate and monitor noise exposure levels that identifies workers at risk. The threshold to provide an OSHA Hearing Conservation Program is that of 85 decibels (dB) or above averaged over an eight hour day. But as damage may also occur accruing from sporadic and intermittent noise, the range of exposure must be monitored from 80 dB to 130 dB. Employers must provide hearing protection in the workplace for these individuals, the type and extent of such can be calculated from the average noise exposure level. Baseline and annual hearing tests must also be provided to these individuals to assure adherence to the Hearing Conservation Program, that progressive hearing loss does not occur. Prevention is paramount, as NIHL is progressive and permanent.
Although the higher pitches of hearing (frequency) are usually the first lost, it is the volume (amplitude), of sound, measured in decibels (dB), that causes damage. Examples of common volumes are: whisper at three feet = 30 dB, conversation at three feet = 60 dB, vacuum cleaner at three feet = 70dB, busy road at fifteen feet = 80 dB, diesel truck at thirty feet = 90 dB, concert three feet from a speaker = 100dB, chainsaw at three feet = 110dB, ambulance siren at 100 feet = 130 dB. The OSHA standard for the work environment is 85 dB averaged over eight hours of exposure. For every three dB of volume increase, the “safe” exposure time is cut in half. At 88 dB, the limit of exposure is now cut to four hours before hearing will become further damaged.
As the work environment is only responsible for about eight hours of our daily living (for most of us), consider the cumulative effect of noise exposure throughout the twenty-four hour day. What is the “safe” level of noise exposure then? According to hyperacusisresearch.org the only evidence-based safe noise level for hearing is a surprisingly low 70 dB when it is averaged over twenty-four hours. Consider personal hearing protection when working with power tools or at sporting events. You may want to turn down the volume on your headphones or earbuds. At maximum volume, you may be generating 100 dB volume, loud enough to begin causing hearing damage at only fifteen minutes of exposure per day. Additional information on NIHL may be obtained from the Occupational Safety and Health Administration link: https://www.osha.gov/Publications/osha3074.pdf or your PCP.
Bradford Croft, DO
East Flagstaff Family Medicine