Section: 16 | Selection of Hearing Protection Devices |
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The recommended form of citation is:
John R. Rumble, ed., CRC Handbook of Chemistry and Physics, 103rd Edition (Internet Version 2022), CRC Press/Taylor & Francis, Boca Raton, FL.
If a specific table is cited, use the format: "Physical Constants of Organic Compounds," in CRC Handbook of Chemistry and Physics, 103rd Edition (Internet Version 2022), John R. Rumble, ed., CRC Press/Taylor & Francis, Boca Raton, FL.


Sonja G. Ringen and Thomas J. Bruno

There are many sources of noise in the laboratory, and generally employers are required to identify employees exposed to noise in excess of 85 decibels (dB) averaged over eight working hours. It is best to apply engineering and administrative controls to mitigate these exposures. If, after applying engineering and administrative controls, sound levels in the local environment are higher than regulatory or recommended levels, hearing protection devices (HPDs) should be used to reduce noise exposure (Ref. 1).

The following table provides a range of sound levels (in decibels, dB) for common laboratory equipment.


Equipment Sound level range (dB)
Air compressor 75 – 95
Shaker table 75 – 85
Pressure-relief valves 75 – 120
Pressurized vortex tubes 75 – 85
Sonicator (probe type) 70 – 110
Fume hood 30 – 70
Vacuum pump 50 – 70
Room air conditioner 30 – 65

In addition to the noise generated by various devices in the laboratory, additional noise can be generated by devices not directly related to the function of the lab. Noise from radios, piped-in music, HVAC systems, and telephones are also present in many laboratories.

It is not necessarily optimal to use hearing protection that simply maximizes sound attenuation; it remains important for workers to communicate with one another. Thus, devices that prevent intelligible speech can be problematic. Moreover, one must be able to recognize laboratory equipment alarms (such as low flow alarms on fume hoods, temperature alarms on ovens, and in some environments, backup alarms on forklifts, etc.). In many cases, personnel will remove hearing protection to communicate with one another or to listen for an alarm, even though removal of an HPD in a high noise environment can substantially reduce hearing protection. By choosing the right hearing protection, removal of the HPD by personnel can be minimized. In the United States and other industrialized countries, sound levels must be determined so that the correct noise reduction rating may be determined, and training must be provided by an industrial hygienist or other appropriate personnel.

Clearly, hearing protection can only be effective if it is actually used, so user preference (between earplugs and earmuffs, for example) must be considered. Because the anatomy of the ear varies with each individual, the effectiveness of earplugs might not be universal, especially if inserted incorrectly. Moreover, in some environments, personnel inserting and removing earplugs through the course of a workday can introduce dirt and bacteria and cause ear infections. When a higher noise reduction rating (NRR) is needed, sometimes using two styles of HPDs concurrently is effective, e.g., earmuffs and disposable foam earplugs, although the NRR is not simply additive. The following table provides guidance in choosing the appropriate HPD. 

Note in addition to the equipment shown below, there are combination devices available. One can obtain, for example, a passive earmuff combined with a protective hard hatand various types of face shields.


  1. Schulz, T., and Madison, T., Hearing Conservation Manual, Fifth Edition, Council for Accreditation in Occupational Hearing Conservation, Milwaukee, WI, 53202, 2014.
Type Illustration Notes
Passive Earmuffs passive earmuff Easy to fit; good for intermittent noise exposure, multiple headband types are available to accommodate other protective equipment such as hard hats; may be uncomfortably hot or heavy; more expensive than earplugs.
Disposable Foam Earplugs Disposable Foam Earplug Cooler than earmuffs, and often more comfortable for extended use; can provide most attenuation; multiple sizes for different ear canals; attenuation depends on proper fit; proper fitting may be difficult to achieve or learn; hygiene issues in dirty environments; can absorb perspiration; single-use only.
Pre-Molded Reusable Earplugs Pre-Molded Reusable Earplug Comfortable for extended use; washable and reusable; do not absorb perspiration; multiple sizes for different ear canals; attenuation depends on proper fit; slightly more expensive per unit than the disposable earplugs above; must be cleaned between uses; may become loose with talking and chewing.
Canal Caps/ Semi-Insert Earplugs Canal Caps Semi-Insert Earplug Convenient for intermittent use; various noise reduction ratings available; hangs around neck when not in use; lower attenuation than most earplugs; lower noise reduction ratings than earmuffs or earplugs; wearer’s voice sounds louder (occlusion effect).
Custom Earplugs Custom Earplug Comfortable with proper insertion; active sound management; variability in attenuation; comfort and fit variable with changes in ear canal; higher initial cost than other earplugs; quality can be variable.
Combination Earmuff Combination_earmuff_16_28.jpg Easy to fit; face shield or face screen available; might be less adjustable than individual components; may be uncomfortably hot or heavy; more expensive than earmuffs or earplugs; often more expensive than individual components.
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