Hearing Conservation Archive: E-A-Rlog

The E-A-RLog series of technical monographs on hearing and hearing protection was originally introduced in 1979 to provide up-to-date research and educational information to the customers of what was then E-A-R™ Division. Since that time, twenty–one technical monographs have been published.

E-A-RLog technical monographs are peer-reviewed by independent experts prior to publication. This highly acclaimed series has appeared in eleven journals, is read in over 36 countries and is utilized by the U.S. armed forces, OSHA, CAOHC and more than 70 universities as educational materials for hearing conservation training courses. Moreover, it was heavily cited by the Mine Safety and Health Administration (MSHA) in their revised 1999 noise regulation. Selected technical monographs have been translated into Danish, German, French, Portuguese and Swedish, and others have been reprinted as contributed technical articles in magazines and journals in the U. S., Canada, Europe, Australia and Brazil.

There have been strides in understanding hearing protection function and performance in the years since the first technical monograph was published. This evolving series has reflected that fact by incorporating the most current information available at the time of publication. Certain technical monographs (1, 2, 15, 16 and 21) contain information that has been supplanted or has become dated. Those are not available for download; however, copies may be obtained by special request.

E-A-RLog technical monographs are provided as a courtesy and may be reproduced only in their entirety and with clear copyright reference to 3M.

  Overview and Index to the E-A-RLog™ Series Numbers 1-21 (97 KB)

The E-A-RLog Index provides an overview of the series on its back page, with initial publication dates and the languages into which selected E-A-RLogs have been translated. The body of the index provides a key word index for the entire series.

1 - The Threshold Shift Method of Measuring Attenuation
This document contains information that has been supplanted or has become dated. Copies may be obtained by special request.

2 - Single Number Measure of Hearing Protector Noise Reduction
This document contains information that has been supplanted or has become dated. Copies may be obtained by special request.

3 -   The Effects of Hearing Protectors on Auditory Communications (52 KB)

4 -   Performance of Hearing Protectors in Industrial Environments (72 KB)

5 -   Hearing Protector Performance: How They Work (205 KB)

6 -   Extra-Auditory Benefits of a Hearing Conservation Program (42 KB)

7 -   Motivating Employees to Wear Hearing Protective Devices (391 KB)

8 -   Responses to Questions and Complaints (Part I) (42 KB)

9 -   Responses to Questions and Complaints (Part II) (39 KB)

10 -   Responses to Questions and Complaints (Part III) (42 KB)

11 -   The Hearing Conservation Amendment - Part I (41 KB)

12 -   The Hearing Conservation Amendment - Part II (117 KB)

13 -   Attenuation of Earplugs Worn in Combination with Earmuffs (70 KB)

14 -   Protection for Infrasonic and Ultrasonic Noise Exposure (70 KB)

15 - Workers' Compensation for Occupational Hearing Loss
This document contains information that has been supplanted or has become dated. Copies may be obtained by special request.

16 - A New Hearing Protection Attenuation Standard - ANSI S12.6
This document contains information that has been supplanted or has become dated. Copies may be obtained by special request.

17 -   Ear Infection and the Use of Hearing Protection (79 KB)

18 -   Can Hearing Aids Provide Hearing Protection? (75 KB)

19 -   Tips for Fitting Hearing Protectors (110 KB)

20 -   The Naked Truth About NRRs (55 KB)

21 - Hearing Protector Testing - Let's Get Real
This document contains information that has been supplanted or has become dated. Copies may be obtained by special request.

Fitting 3M™ E-A-R™ Foam Earplugs (PPT, 1.9 MB)
This slide set is designed for a quick presentation on how to fit foam earplugs. It clearly demonstrates proper roll down and insertion via photos of actual plugs and ears.

  The Noise Manual, 5th Edition (676 KB)
The bible on Noise and Hearing Conservation, following in the footsteps of AIHA's 4th Edition. Read the first chapter entitled Noise Control and Hearing Conservation: Why Do It? by Elliott Berger.

  Soundscape, the Journal of Acoustic Ecology (2.2 MB)
A special issue of Soundscape, the Journal of Acoustic Ecology magazine, posted with permission of the World Forum for Acoustic Ecology (WFAE), devoted to hearing loss - how it occurs, how to use hearing protection to prevent it, the use of hearing aids to restore it, and the impact of tinnitus.

  The Ardent Hearing Conservationist (66 KB)
A reprint of a paper presented at the 2001 annual conference of the NHCA. A collection of Elliott Berger's favorite tips on motivating employees in a hearing conservation program.

  Active Noise Reduction (ANR) in Hearing Protection (85 KB)
A reprint of a paper presented at the 2002 annual conference of the National Hearing Conservation Association that analyzes the performance of a top-performing ANR device in 300 representative industrial noise environments and draws conclusions about the applicability of such devices in industry today.

  International Review of Field Studies of Hearing Protector Atten. (918 KB)
A reprint of Chapter 29 from Scientific Basis of Noise-Induced Hearing Loss that analyzes and reviews data from 22 field studies from around the world.

  Technology Advancements in HPDs (2.4 MB)
A reprint of a 1995 paper from the American Industrial Hygiene Association Journal on developments in active noise reduction, electronic hearing protection, passive frequency and amplitude sensitive devices, and recommendations for use of such devices.

  A New Hearing Protector Rating (1.5 MB)
In 2003 the U. S. EPA announced their intention to revise the hearing protector labeling regulation. As part of the process, the EPA requested a report from ANSI S12/WG11, chaired by Elliott Berger, on recommendations for new hearing protector ratings. This report by Gauger and Berger was completed in 2004.

  Limits To Attenuation (1.4 MB)
A reprint of a peer-reviewed paper published in the October 2003 issue of the Journal of the Acoustical Society of America that examines the bone-conduction limits to hearing protector attenuation and provides estimates of the most protection deliverable, even if one totally encloses the head.

  Preferred Methods for Measuring Hearing Protector Attenuation (1.1 MB)
Presented at Inter-Noise 2005, this article examines the three most robust methods of measuring hearing protector attenuation, including real-ear attenuation at threshold, microphones in real ears and the use of acoustical test fixtures.

  Options in Defining Background Noise During Audiometric Testing (105 KB)
Published in the NHCA Spectrum and the CAOHC Update, this article examines current limits to background noise during audiometric testing and issues that arise when those limits are not met.

  Children and Hearing Protection (536 KB)
Reprint of an invited presentation at the first ever conference on Noise-Induced Hearing Loss in Children at Work & Play.

  Development and validation of F-MIRE technology (3.6 MB)
Reprint of an invited peer-reviewed paper, from a 2011 special issue of Noise & Health, that examines and validates the technology behind F-MIRE measurements of hearing protector attenuation.

Comparison of OSHA, MSHA, FRA, and NIOSH Regulations and Recommendations (XLS, 45 KB)
This document provides an overview of the OSHA (Occupational Health and Safety Administration), MSHA (Mining Safety and Health Administration), FRA (Federal Railroad Administration) and Construction hearing conservation regulations as compared to the NIOSH (National Institute for Occupational Safety and Health) recommendations for best practice.

Comparison of Regulations Across Canada (XLS, 194 KB)
This excel spreadsheet provides an overview of the regulations in the 13 Canadian Provinces and the Canadian Federal Government.

Fitting Foam Earplugs (ZIP, 82.9 MB)
This single–topic film is a clear demonstration, including animation, of how to fit foam earplugs. This film is excellent to include with your annual training programs or to excerpt and insert in your own training videos or PowerPoint files (5 min).

Fitting Premolded Earplugs (ZIP, 97.6 MB)
This single–topic film is a clear demonstration, including animation, of how to fit premolded earplugs. This film is excellent to include with your annual training programs or to excerpt and insert in your own training videos or PowerPoint files (5 min).

Fitting Push-In Style Earplugs (ZIP, 97.8 MB)
This single–topic film is a clear demonstration, including animation, of how to fit push-in style earplugs. This film is excellent to include with your annual training programs or to excerpt and insert in your own training videos or PowerPoint files (5 min).

Auditory Transduction (ZIP, 81.2 MB)
With exciting 3-D animation and a dramatic classical sound track, this video takes us on a trip through the ear to vividly explain how we hear. Auditory Transduction is definitely "best of breed" on the topic. Brandon Pletsch of Thomas Direct Studios (thomasdirectstudios.com) has given permission to 3M to post this video. To learn more about this National Science Foundation award winning film, or you can contact Mr. Pletsch directly: bpletsch@thomasdirect.com (7 min)

Sound of Sound Excerpt (ZIP, 8 MB)
Three excerpts from steel workers who have suffered the angst of hearing loss and tinnitus due to noise provides glimpses of how it has affected their lives. Though the original film was produced in 1970, these excerpts present an emphatic and timeless message (1 min).

  Audio Demonstration Series information (57 KB)
The Audio Demonstration Series consists of two programs intended to introduce concepts in hearing and hearing conservation and to amplify them via sound clips recorded with state-of-the-art fidelity and realism. The programs each run about 15 minutes in length and are suitable for use in high school, undergraduate, and graduate college classroom, CAOHC courses, seminars, and customer sales and education. Educators should feel free to excerpt passages most relevant to their program.

Noise Hazards – Hearing Conservation

1. How loud is it?
See our simplified   noise thermometer (464 KB) or   3M™ Noise Navigator™ (286 KB) database of more than 1700 noise sources

2. How does noise cause hearing loss?
See the Nature of Hearing and Hearing Loss in the special issue of     Soundscape (2.16 MB) magazine.

3. Gunfire - How dangerous is it to my hearing?
The sound of gunfire is the most hazardous non-occupational noise to which Americans are exposed. The table below lists the peak sound pressure levels of typical guns. What is so dangerous about peak levels such as these is that a single shot experienced by an unprotected ear can lead to immediate and permanent hearing loss, often accompanied by tinnitus (ringing, hissing or humming in the ears). Just because you might have shot without protection in the past, and without apparent hearing loss, does not mean you might not get hurt the next time. Exposure to peaks sound pressures can be likened to dropping a glass bottle. Sometimes it breaks and sometimes it doesn't; you can't predict the outcome.

Hearing protection should always be worn when firing guns. Some will even choose to use dual protection because it reduces the sounds even further for greater protection, and for some, for better shooting as well (since the pulses are lower and the likelihood of flinching is reduced).

Peak Sound Pressure Levels (SPLs)
Type of Gun      SPL (dB)
.44 Revolver      170 dB
45 Automatic      165 dB
M-16      160 dB
.357 Revolver      160 dB
12 Gauge Shotgun      155 dB
.38 Revolver      150 dB
.22 Rifle      145 dB

4. The 'noise pill' - Will it protect me from hearing loss?
  See the answer (113 KB)

5. Loud music during exercise and its effects on hearing
  See the answer (91 KB)

6. Automotive airbags - Can their deployment cause hearing loss?
  See the answer (30 KB)

7. Is my personal music player (MP3) hurting my hearing?
  See the answer (4.89 MB)

8. Tinnitus and Hearing Protection: Fiction and Fact
  See the answer (90 KB)

Hearing Protection

1. Fit testing - how do I do this in the workplace?
  See the answer (116 KB)

2. PAR - What does this fit-testing rating mean?
  See the answer (246 KB)

3. Dual protection - What can I gain from wearing a plug and a muff together? Can any protector block all sound?
Dual protection is normally recommended for noise environments with exposures exceeding a time-weighted average level of 105 dBA, or for users who simply wish to block additional sound for extra protection or reduced annoyance.

When using dual protection, especially for low-frequency noise, the earplug you select is the key. We suggest a high-quality foam plug like the E-A-R™ Classic™ or E-A-Rsoft™ foam earplug together with a small and comfortable earmuff such as the Peltor™ H6 earmuff. Once you have properly inserted the earplug (see   Tips and Tools for Fitting and Using E-A-R™ Foam Earplugs (2.18 MB) ), the selection of a particular earmuff is essentially unimportant. Therefore, smaller, lighter, less-expensive choices make the most sense. Alternatively you can select from any of our foam or pre-molded earplugs together with an E-A-R or Peltor muff of your choosing (see&   E-A-RLog™ 13 (69 KB) ), for additional details on attenuation to be gained when products are combined). In general, combined protection provides approximately 5-dB gain over the more protective of the individual devices at most frequencies.

As for "blocking all sound," that is not possible. Even when noise is effectively stopped from entering the earcanal, it can "get around" the hearing protector (technically called bypassing the hearing protector) by vibrating the bones of the head and neck to directly stimulate the inner ear. See   E-A-RLog 5 (204 KB) and   E-A-RLog 13 (69 KB) for additional details. Also, if you place your head on a vibrating object while wearing a hearing protector (for example lean your head against the exterior cabin wall of a jet while wearing earplugs during flight), you will often notice a substantial increase in the sound level, since you are coupling your head more effectively to the vibrating object and thereby increasing the efficiency of the bypass process.

NOTE: When wearing an earmuff and an earplug, OSHA gives credit for 5-dB of additional protection above that of the higher attenuating device. See the OSHA Technical Manual.

4. What type of hearing protector blocks out the most noise?
  See the answer (96 KB)

5. Air travel - Use of earplugs in airplanes
  See the answer (35 KB)

6. Children - Hearing Protection / Swim Protection
  See the answer (35 KB)

7. Comparing hearing protector ratings - NRR, SNR, SLC, and others
  See the answer (168 KB)

8. Tinnitus - Hearing protection recommendations
  See the answer (43 KB)

9. What does the caution statement on hearing protector packages about frequencies below 500 Hz and the use of "C-weighted environmental noise levels" mean? Does it indicate that the plugs are not appropriate in those environments?
The cautionary statement has to do with how to compute protection; it has nothing to do with the performance of the product per se.

The cautionary statement's precise wording is required by the U. S. Environmental Protection Agency (EPA). It appears on the labeling for all hearing protectors sold in the U. S. and pertains to the fact that when the mathematics behind the NRR was developed, the rating was intended to be subtracted from dBC, rather than dBA sound levels. Regardless, the EPA directs the user (also in prescribed wording) to subtract NRRs from A-weighted, and not C-weighted sound levels in order to compute protection. Both procedures give about the same answer when the dBA and dBC values are equivalent; when they are not, which occurs when there is substantial energy below 500 Hz, then the "incorrect" approach of using the dBA values will be underprotective. This is the reason for the "below 500Hz" warning. In spite of this potential error, EPA selected dBA for the example computation because A weighting is much more commonly utilized than C weighting, and it is the weighting specified by OSHA to regulate permissible noise exposure.

EPA presumes, and correctly so, that most consumers (and the labeling regulation was heavily influenced by the needs of the consumer market) would not be able to measure C-weighted levels or understand what they mean. Unfortunately, most consumers are also unable to tell if noises are "dominated by frequencies below 500 Hz," and hence they are unable to determine whether the use of C weighting is required.

For a more comprehensive description of the use of NRRs with dBA and dBC sound levels see p.2 of   E-A-RLog 12 (117 KB). For a discussion of the meaning of A weighting, and a comparison of A and C weighting, see the question on that topic under Sound, Sound Measurements and General Hearing Topics. The comparison of A and C weighting shows that they primarily differ in the low frequencies, which is why the EPA's cautionary statement only applies below 500 Hz.

10. Noise-cancellation earmuff - Is there a type that might help someone wearing hearing aids and working in noise?
  See the answer (116 KB)

11. Foam earplugs - Who invented them and when were they introduced?
  See the answer (160 KB)

12. Are custom earplugs the best fitting and protecting type of earplugs?
  See the answer (2.9 MB)

13. Do non-electronic "valve-type" earplugs like the Combat Arms earplug really work?
  See the answer (335 KB)

14. How do HPDs affect my ability to hear in noise?
  See the answer (127 KB)

Sound, Sound Measurements and General Hearing Topics

1. dBA and dBC - What do these terms mean?
The letters "A" or "C" following the abbreviation "dB" designate a frequency-response function that filters the sounds that are picked up by the microphone in the sound level meter. A frequency-response function, also called a weighting characteristic (meaning that some frequencies are given more weight or importance than others) can also be thought of as a tone control. It emphasizes or de-emphasizes sounds of certain pitches relative to others. The actual influence of the A- and C-weighting functions is illustrated in the Figure. The vertical axis shows relative response in decibels and the horizontal axis shows frequency measured in Hz or cycles/sec. (which is a measure of pitch).

Notice that the A weighting filters out the low frequencies and slightly emphasizes the upper middle frequencies around 2-3 kHz. By comparison C weighting is almost unweighted, or no filtering at all.

A-weighting is used to measure hearing risk and for compliance with OSHA and MSHA regulations that specify permissible noise exposures in terms of a time-weighted average sound level or daily noise dose. C-weighting is used in conjunction with A weighting (the dBA and dBC levels are compared) for certain computations involving computation of hearing protector attenuation such as use of the NRR.

For information on the use of dBC with the NRR, see   E-A-RLog 12 (117 KB).

2. What criteria should a professional reviewer use to revise baseline audiograms when an STS is detected?
  See the answer (664 KB)

3. How do I correctly measure sound exposures from iPod® -like devices?
  See the answer (91 KB)

4. Can hearing aids bring my hearing back?
See the Restoring the Soundscape with Hearing Aids in this issue of   Soundscape magazine (2.16 MB).