The authors discuss the need for hearing conservation programs and annual hearing testing in the workplace.
A sound booth or acoustic enclosure is needed for testing when ambient noise cannot be controlled.
Americans are exposed to noise pollution on a regular basis. Exposure to loud noise occurs in the workplace, in the home, and in recreational areas. Prolonged exposure to high noise levels over a period of time can gradually cause permanent damage. Approximately 30 million workers are exposed on their jobs to noise levels that are potentially hazardous to their hearing. This noise-induced hearing loss can be reduced, and even eliminated, through successful hearing conservation programs.
A good hearing conservation program includes noise monitoring, noise controls, employee training, audiometric testing, and hearing protection. While it is relatively easy to offer hearing protection to noise-exposed workers, it is sometimes difficult to provide routine audiometric testing.
Audiometric testing monitors an employees hearing as well as providing an opportunity for employers to educate employees about their hearing and the need to protect it.
It is important to test workers hearing annually to identify deterioration in their hearing ability as early as possible. Employers must conduct audiometric tests in a room meeting specific background levels and with calibrated audiometers that meet American National Standards Institute (ANSI) specifications.
Is a Sound Booth Needed?
To determine whether an acoustic enclosure or sound booth is required, it is important to identify the noise levels in the environment to be used to perform any hearing screening tests. To make a proper decision, a number of questions need to be answered. First and most important, the existing ambient sound pressure must be measured. Second, location outlay, accessibility, and usage must be taken into account.
Each site will have unique situations, but they can be broadly separated into four categories;
1. The location environment is naturally quiet enough to meet the desired interior ambient.
2. Room treatment is required. Anticipated interior ambient is not severe enough to require installation of a sound booth, but does require some sort of treatment. Typically, these treatments would include some or all of the following;
a. Acoustic door installation
b. Interior absorptive treatment
c. HVAC baffle installation
d. Acoustic windows
3. Small screening booth is required. For areas where there is high enough ambient noise that cannot be controlled by altering the existing room, but the area is not so harsh that it warrants a audiometric-quality booth.
4. Audiometric booth. Location has a high enough ambient to require a sound booth to meet ANSI requirements.
The process would begin with a sound survey. Figure 1 displays what a typical survey might look like. There are many ways to have a sound survey done, ranging from inexpensive and easy-to-use to extremely expensive and detailed. An example of an inexpensive method would be using a rudimentary single number sound level meter (available for under $100). Ambient sound pressures should be sampled normal maximum sound pressure levels (SPL).
The other extreme is to hire a consultant. A consultant will have specialized equipment and ASTM procedures for taking readings. These readings will be very accurate, but the cost is clearly higher. The chart (Figure 1) was taken with a device that took digital readings on a handheld device (PDA). Unlike the inexpensive solution, this method identified the octave band levels, which are needed to pinpoint problem areas. While not as accurate as a consultant, it gives an idea of not only if there is a sound issue, but also where the problem areas occur.
Once the ambient sound pressure is determined, the first step is to compare it to the desired level (Figure 2).
Clearly in this example, there is a gap between what is desired (30 dB) and what was measured.
The next step would be to overlay the broad stroke acoustic recommendations. This sample shows a big differential, but to look at the effects each broad category would have, we show the resulting lines on the graph.
Broad Category 1: The chart (Figure 2) shows clearly that action is needed in this site
Broad Category 2: Room treatment would not meet the required standard, as shown in Figure 3. It does help, but not enough.
Using the same technique, a small screen booth would do better, but not completely hit the goal as shown in Figure 4. Note the higher frequencies are satisfied, but the lower ones are still a problem. This kind of analysis could not have been done with the simple sound level meter, such as the inexpensive option mentioned above.
And finally, Category 4. This shows the full audiometric booth is needed in this particular location as shown in Figure 5.
Note all bands are covered, with the exception of 125 Hz. The slight deficiency shown would be within acceptable tolerances in all but the most precise environments. For the purposes of hearing screening, it would be incidental.
This overview is a hands-on approach to a system to evaluate testing environment needs on a thumbnail example. In many cases, it will make the situation needs clear, thus making the decision process quick and easy. Other times, it may only alert one to a more complex situation, but even then, the experts can be called in with the assurance that they are truly needed.
Margana Huff is marketing director of Acoustic Systems, Austin, Tex. Steve Dutton is business development manager.