Q&A – How does noise affect alertness?
Why can soothing music or “white noise” can put you to sleep, while a loud alarm every five minutes has the opposite effect? Noise and alertness have a complex relationship.
Research finds that even the same noise can evoke varied responses in different individuals. For example, a study that simulated an assembly line found noise actually improved the speed of air conditioner assembly but reduced the speed for carburetor assembly. While noise’s effects are not yet perfectly understood, consensus exists on a number of points:
Continuous loud noise is dangerous and can cause hearing loss. The National Institute for Occupational Safety and Health (NIOSH) recommends that the noise level not exceed 85 decibels (dB) —comparable to the sound of a lawnmower or electric drill. According to NIOSH, one in eight people exposed to a noise level over 85 dB develop hearing loss.
Continuous loud noise may reduce performance. Noise’s effect on performance depends on what kind of work one performs. For example, noise’s effect is negligible if a person has to react at certain definite times, receives clear warning signals, and has an easily visible stimulus, according to research. But problems arise when people perform a monitoring task for a long time and warning signals are less clear, or a task has several components.
Although performance problems may not always show up in lab tests, it’s still a good idea to minimize the noise level as much as possible. Along with effects on performance and hearing, excessive background noise can cause stress and anxiety and interfere with memory and learning.
“White noise” causes on-the job problems for shiftworkers. White noise — a mix of sound waves extending over a wide frequency range — is commonly generated by engines, computers, and machinery.
At work, white noise often has the effect of lulling people to sleep, especially shiftworkers struggling to stay awake during the overnight hours.
Technology can reduce noise. There are specially-designed headsets that can reduce the external noise level by about 23 dB and allow wearers to listen to music that automatically mutes when a co-worker or supervisor needs to communicate.
Noise cancellation may minimize the effects of noise on alertness. Noise cancellation devices are often built into earmuffs and produce a low-frequency noise wave that is the exact mirror image of the existing noise. Sometimes called “anti-noise,” these devices do not eliminate noise altogether, but they provide 15-20 dB of noise reduction. If your work environment has a lot of loud noise, or continuous white noise, suggest noise cancellation headphones to your shiftworkers.
Smith, A. “Noise, performance efficiency and safety” Int Arch Occup Environ Health (1990) 62:1-5.
- Shift Scheduling Homepage - Learn more about shift scheduling, staffing levels, and expanding to a 24/7 operation
- Managing a Shiftwork Lifestyle Training Program
- Working Nights Newsletter