Many users in a group may obtain values close to the labeled NRR, but a substantial portion typically do not. The only way to determine a person’s attenuation level is with a fit test system.

    * By Lee D. Hager, Pegeen Smith
    * Sep 01, 2010

Editor’s note: Fit testing is not just for respirators. It is a good way to determine whether that worker’s hearing protector is adequately attenuating the noise to which he or she is exposed, especially in high-noise situations, the authors note in the following Q&A.

Q: Why should I consider fit testing hearing protectors?

A: Individual fit testing of hearing protection devices (HPDs) can lead to significant improvements in several aspects of your hearing conservation program.

* Train and motivate employees. Providing workers with a quantitative measure of how well their HPDs can work can help to ensure they understand proper use.

* Train the trainer. Most HPDs are distributed by people with limited experience in HPD fitting. Fit testing helps educate those who perform fit checks on what a proper HPD fit looks, sounds, and feels like to enhance their ability to train others.

* Helps select HPDs. Differences in ear canal size and shape and differences in a worker’s ability to prepare an ear plug for use are reflected in individual fit test results. Fit testing can help find the HPD that is right for the worker and noise environment.

* Provide standard-threshold-shift (STS) follow up. When hearing loss of a particular configuration is found in a noise-exposed worker, OSHA requires that the HPD used by that worker be assessed to determine whether it provides adequate noise reduction for the worker’s exposure. Fit testing can help provide the required OSHA follow-up.

* Determine HPD adequacy/sufficiency. Especially in high-noise situations, it can be important to make sure the HPD is providing enough noise reduction to lower the worker’s noise exposure sufficiently. Comparing noise exposure data with the HPD fit testing data helps employers make this determination for each individual employee.

* Audit departments. It can be useful in hearing conservation program administration to compare hearing loss results from different groups, sites, or departments. Fit testing is another piece of the puzzle that may help to identify individual employees who need additional assistance to wear hearing protection successfully.

* Demonstrate adequacy of training. Fit testing can be a quantifiable way to make sure trainees can properly fit and use their HPDs after training. Conducting fit testing after training is one way to document whether or not the training was effective.

* Provide documentation. Fit testing reports may be used to document how well the employee fitted the HPDs at the time of the test and which HPD was selected for that employee.

Q: How is fit testing done?

A: Some fit testing systems are based on subjective responses from the person being tested, while other systems measure the fit objectively. Fit testing systems that are based on subjective measurement techniques typically require the employee to participate in a hearing test with the HPD in place (occluded) and a second hearing test with the HPD out (unoccluded).

It may be a hearing test like the one conducted as part of the hearing conservation program, or it may be a different type of hearing test. Although the specifics vary from one system to the next, most, if not all, of the subjective fit test systems require the test subject to listen and respond to a sound signal or “auditory stimulus.”

By contrast, objective fit test techniques involve a direct measure of sound pressure level under the HPD while it is in the ear, for example, taking direct measurements of sound pressure levels inside and outside the ear canal while the HPD is in place and comparing those measurements to determine how much noise reduction the HPD provides.

Q: What are some of the barriers to using these technologies?

A: Subjective systems are just that: subjective. The systems depend on the employee to reliably and consistently respond to the test sounds and are subject to all of the variability that would be expected from a hearing test, such as background noise, employee cooperation, etc. Typically, audiologists are very pleased to obtain test-retest results within 5 dB for hearing tests in industrial settings. The accuracy of subjective fit tests could be expected to be no better.

Objective systems require that a measurement microphone be able to access the sound pressure level in the ear canal while the HPD is in place, using special test ear plugs equipped with a sound tube that can accommodate a measurement microphone. The system generates a test signal and performs all necessary measurements so the employee does not have to respond to the test sound.

Q: What kind of information can I expect to get from these systems?

A: Most systems generate a Personal Attenuation Rating (PAR) that reflects how much noise reduction the HPD is providing as it was fitted that day. Because there is no standardized way to calculate PAR, each system may use a different approach, and the results may not be comparable among systems.

Q: Is a PAR the same as an NRR?

A: No. The noise reduction rating (NRR) printed on the label of the HPD is intended to provide an estimate of the average amount of noise reduction a group of individuals might obtain when wearing a particular hearing protector. These ratings are based on a small group of test subjects who fit the devices in a laboratory setting. Unfortunately, it is not possible to predict the noise reduction obtained by an individual worker from the average noise reduction obtained by a group of test subjects. The PAR represents the noise reduction obtained by the individual worker during a given testing session, rather than a test panel.

Q: Is the employee’s fitting technique the only variable in hearing protector fit?

A: No. Every employee is slightly different. Even though gender, ethnicity, and age may influence the size or shape of ear canals, only a fit test can determine whether a particular HPD is right for that specific ear. In addition, human factors come into play. For a worker with dexterity issues, the need to prepare an HPD before use (for example, by rolling down a foam ear plug) may make it difficult to get enough noise reduction from the HPD for that worker.

Q: Is the noise reduction rating (NRR) on the label a reliable way to determine what level of noise reduction people are getting?
A: No. Research findings, including new research with the E-A-Rfit™ System, indicate the amount of noise reduction people obtain from their choice of HPD varies widely. While many users in a group may obtain values close to the labeled NRR, a substantial portion typically do not. The only way to determine the level of attenuation a person is receiving is with a fit test system. The reasons individuals fail to achieve NRR levels of protection are manifold due to such factors as fitting technique, motivation to wear the device correctly, and individual variation in ear canal anatomy that may influence the ability of the ear plug to fit their specific ear canals.
This article originally appeared in the September 2010 issue of Occupational Health & Safety.

About the Authors

Lee D. Hager is Hearing Loss Prevention Consultant for Sonomax Hearing Healthcare, Inc.

Pegeen Smith, MS, R.N., is a certified occupational health nurse who works for Technical Service at 3M Company. She is the Product Specialist for the E-A-Rfit™ Validation System and the leader of the Global E-A-Rfit™ Technical Service Team for 3M. She trains companies interested in the E-A-Rfit™ Validation System and assists them with the integration of this technology into their hearing conservation program.

Source: The Unofficial Apple Weblog (TUAW)

Have you heard? Apparently iPods cause hearing loss. A Journal of the American Medical Association study published in August found that 14.9 percent of teenagers aged 12-19 suffered from hearing loss from 1988-94; 19.5 percent of the same age group had hearing loss from 2005-06. Throw in another statistic, a 100 percent increase in the number of iPods in existence from 2005-06 as compared to 1988-94, and it’s clear what’s behind this statistically significant rise in teen hearing loss.

Or maybe it’s not so clear, after regarding a meta-study from the University of Minnesota. Researchers there found that 15 percent of the university’s marching band members suffered from hearing loss, but after tracking them for a year and averaging out multiple test results, researchers found that more than half of the noise-induced hearing loss disappeared. Those same researchers said that false positive results can account for around 10 percent of the 14.9 percent hearing loss discovered in the 1988-94 JAMA study.

Listening to anything at a high volume for a long enough period of time will induce hearing loss. That goes for your car stereo, speakers blaring at a concert, and yes, iPods. Are more people listening to music via headphones now versus 1988-94? Probably. Is a portion of that increase due to the iPod’s popularity? Almost definitely. Does that automatically mean there’s an epidemic of iPod-induced teen deafness? It certainly sounds like a plausible theory, but with one study already questioning the JAMA results, the question is far from settled.

I will say that I’m occasionally astonished at the volume of music bleeding from people’s white earbuds as they pass by. I can’t listen to music on my iPhone at more than about 60 percent of maximum before it starts to hurt my ears, so I can’t imagine what kind of damage these people are doing to their hearing. There’s really no excuse for it, either. If you’ve got a child with an iPod, setting a volume limit on it is trivial. And if you’re just trying to drive away the noise of the outside world, a decent set of canalphones is a whole lot cheaper and more convenient in the long run than a hearing aid.

[via Cult of Mac]
TUAWNew study questions extent of iPod-induced hearing loss originally appeared on The Unofficial Apple Weblog (TUAW) on Wed, 22 Sep 2010 10:00:00 EST. Please see our terms for use of feeds.

Source: OHSonline.com

Margin of error should be accounted for and the worst-case scenario measurement taken as the reading, particularly when close to an action level.

    * By Bob Selwyn
    * Sep 01, 2010

The industrial environment has changed drastically in recent decades with an increased level of automation within the workplace. This has given rise to many changes in employee work patterns. It used to be the case on the majority of production lines, an employee would stay in one place during his or her shift. Monitoring the worker’s noise exposure with a traditional sound-level meter was the answer.

However, with the increase in completely automated production lines, employees now may supervise several machines. This means they move around from workstation to the next, varying their exposure to noise in a much more dramatic way than previously. This article examines how noise dosimeters play a more important role in these types of noise assessments.

Meter or Dosimeter
The only way to monitor precisely an individual’s exposure to noise is by using either a sound-level meter or a dosimeter. A sound-level meter is a hand-held device that allows a competent third party to take measurements at the operator’s ear with the instrument pointing at the noise source. By repeating this exercise for all operations an employee performs during the day, you can calculate his daily exposure.

Where it is difficult to get close to employees with a sound-level meter, as in the case of forklift truck drivers, or where workers are exposed to many different noise levels, they should wear a noise dosimeter. This is the case more often than not in the modern workplace, where if you are using a standard meter you would have to measure the noise levels at each location, find out how long the worker stays at that location, and then calculate an overall exposure. This can take hours of calculations to perform and will not always result in accurate measurements.

The Use of Noise Dosimeters
If mobile work patterns exist in your workplace and a noise dosimeter fits the bill, it is important to realize precisely how these instruments must be used and understand their limitations. Given the logarithmic nature of the decibel scale, a variance of only 1 or 2dB can often mean serious misinterpretation of noise levels. This margin of error should be accounted for and the worst-case scenario measurement taken as the reading, particularly when close to an action level.

A noise dosimeter consists of a microphone on a cable, which can be clipped to a collar. The microphone cable is then passed under the clothing to the unit itself, which is small enough to be located in a pocket or clipped to a belt. The dosimeter can then be started at the beginning of the shift. If it runs until the end of the working day, the noise dose can be directly read from the instrument or downloaded without the need for calculations. Another useful feature of noise dosimeters is that they will log the noise data so that when downloaded to a PC, the time history of the noise can be viewed. This gives the ability to analyze when and where high noise exposures occur. This can be even more useful when the dosimeter is placed on an employee who is prepared to make a list of the times and jobs he or she was performing throughout the day. This will give the employer the ability to see which operations most need noise control in order to reduce exposure.

A traditional noise dosimeter is fixed to the worker’s belt, and then a microphone on a cable is attached to the collar near to the ear. You should make allowances for human nature. Employees fitted with dosimeters and their colleagues will often shout into the microphones, distorting the readings, so it’s best to ignore the first few days’ results until the novelty wears off.

One advantage of dosimeters is that if employees wear them for complete working shifts, the noise dose is measured in full. However, if you need to make several measurements of different employees in the same day, a dosimeter can be moved to different employees, as long as the measurements taken for each employee are representative of their working day. Most modern dosimeters also will project the noise dose forward to the standard eight hours, so no calculations are needed.

With innovations in digital technology, noise dosimeters are becoming smaller and smaller. The latest “badge” dosimeters have certain advantages over traditional dosimeters. Because the dosimeter is small and light enough to be worn on the shoulder, it means there are no cumbersome microphone cables. If there are no cables to get in the way, not only is it safer to wear, but also employees are less resistant to wearing it and much more likely to forget it is there. This means the quality of the noise data collected will be improved.

Because of the small size of badge-type products, it is also possible to mount them in more innovative ways, such as on a hard hat, close to the ear, without interfering with an employee’s working process in any way. This allows the dosimeter to not be mounted on clothing at all, therefore completely removing it from the employee’s mind.

Also, consider the use of windshields. They play a crucial role in any sound level measurement, even when indoors, to provide protection from dust settling on the microphone, as well as from knocks.

Standards and Accuracy
Noise dosimeters are manufactured to IEC 61252, the international standard for dosimeters. IEC 61252 “Type 2” regulations require a field calibrator of a dosimeter before each use. Field calibrators produce a noise signal, normally a tone of 1 KHz at 114 dB. It is best practice to run the calibration test after any period of field measurement, as well, to check that there has been no significant drift of the dosimeter during the measurement.

The dosimeter and the acoustic calibrator must be returned to the manufacturer for a full calibration every two years for a true calibration. A lab conducts a battery of tests, including testing measurements across all frequencies and levels to ensure the dosimeter still meets the requirements of IEC 61652.

The Post Process
Dosimeters measure all essential parameters for workplace noise regulations such as daily exposures and peak levels. However, to serve a purpose this data must be easily accessible and be presented in a format that is comprehensible to someone not familiar with acoustic terminology. Modern software will give the dosimeter user the ability to store data in a format that accounts for who was being measured, when these measurements were taken, and at what workstation. Software today can output data into reports automatically, including the average and peak time history, in a simplified format with all required data for workplace noise regulations.

Conclusion
Dosimeters are crucial in noise monitoring in today’s modern working environment, with its highly mobile workers and varying noise exposure. Dosimeters provide valuable information by using logged time history data that show exactly when and where specific noise exposure took place. These details allow the implementation of proper controls to prevent hearing damage, which is the true end goal of any noise survey.

This article originally appeared in the September 2010 issue of Occupational Health & Safety.