Hearing and The Work Place
By Charles Betbeze
Return to Hearing Loss Due to Noise
Over 28 million people in the United States have significant hearing impairment most of which is permanent and untreatable . The Environmental Protection Agency estimates that nearly four times that number, about 40 percent of the U. S. population, is exposed to enough noise to cause permanent hearing loss . During the day, suburban noise can be as high as 52 dB and inner city noise at 80 dB . Noise becomes physically painful at 132 dB. The EPA has set 55 dB as the average sage level .
Physician Robert Dobie says that the majority of damage occurs in the first 10 years of exposure. The damage then slows but does not cease . Raymond Hull explains that most of us feel no pain while our ears are being irreversible damaged . He goes on to say: "That’s because the ears automatically adapt to noise. Ever notice how you have to keep turning up the volume on a car radio. After 15 minutes, the ears muffle themselves so that what once seemed loud doesn’t anymore" . Hearing conservation experts stress that prevention is the key to elimination of noise-induced hearing loss . The problem is that protecting the ears causes problems, which will be discussed later.
Areas were the noise level is to high can be found almost anywhere. Audiologist Raymond Hull found that 90 percent of health clubs and spas he monitored had music levels above 105 decibels for aerobic and body conditioning classes . Two-thirds had levels over 110 decibels . Some of these clubs and spas had levels of music above 124 decibels . According to OSHA a person can sustain permanent damage can accrue from 7.5 minutes of exposure at 120 decibels . These people are in classes for 40 minutes or more a couple times a week, week after week, month after month . The instructors are teaching these classes 8 to 10 hours a week could be at even high risk a hearing damage then the students .
Another line of work were people are exposed to high levels of noise is farming. The findings showed that farmers did not have a clinically significant hearing loss . However, 10 percent of the age 30 farmers, 30 percent of the age 40 farmers, and 50 percent of the age 50 farmers had a hearing handicap . This information shows that farmers hearing gets worse as they get older.
There are some things to consider when talking about hearing loss and protecting the ears from hearing loss. A history of ear infections can affect the amount of hearing loss. Warring ear protection can affect a persons ability to know which direction a sound is coming from. And the location of the sound source can affect the response time of people warring ear protection.
A study of 1194 young men from 18-24 years old found that repeated episodes of otitis media (ear ache) had higher percent of hearing loss . Of total population, 38 percent had a slight increase in hearing loss in men who went to concerts and discos twice a month or more . Men who had noisy occupations, 18 percent, had an even smaller increase in hearing loss. The biggest increase in hearing loss was among men that used personnel stereo users . This harmful effect was strongly dependent on the presence of repeated episodes of otitis media in infancy or childhood . Below is a graph of the findings from this study.
People with a history of hear ache should be warned of the effects that personnel stereos can have on their hearing. And if they worked in a noise occupation their employers should be aware of this potential problem.
A study of occupational injuries found that older workers with disabilities were more likely to get heart on the job. Among 5034 workers 51 to 61 years old had a 1.72 odds ratio of getting heart well working . The data was from 1992 to 1996 and 580 of the 5034 were injured during this time . Of the other disabilities, hearing problems had elevated odds ratios . It is important that employers keep this information in mind when dealing with older workers.
The next study was done to study the effects of wearing headgear and earplugs. The experiment was divide into 4 parts: no earplugs or headgear, headgear only, earplugs only, and headgear with earplugs. The participants were position in both frontal and lateral orientation. With the speakers positions as soon below.
The frontal orientation did not have a lot of errors . But the lateral orientation varied over a large range due to a front-back confusions when wearing headgear or earplugs . The barehead part of the experiment was used as a base line to compare the rest with. In the frontal orientation the kalviar helmet differed little from the barehead . There were some small errors in the lateral orientation . Wearing earplugs only there was little error in the frontal orientation . Below is some of the test results.
The biggest amount of confusion come from wearing both headgear and earplugs . The chart below is for earplugs only in the lateral orientation.
On the other hand, in the lateral orientation there were a lot of errors . The table below shows the different comparisons and their results.
The graph below is a comparison of the frontal and lateral orientation for each part of the experiment .
The results from this study can help when deciding weather or not to use auditory signals and the effects of wearing hearing and head protection .
Another experiment was down to see if response time to auditory stimuli would increase with the information content of the stimuli. In this experiment participant were seated in the middle of a 6 speakers and asked to identify which speaker the sound came from and then perform some type of operation. A layout of each experiment is soon below along with the results.
Each experiment was set up as follows: in experiment 1 the directions came from all 6 speaker, in experiment 2 the directions come from the front 3 speakers, and in experiment 3 the directions come from speakers symmetrically located from each other. The experiment found that increasing the number of locations from which an alarm can sound, increases the time it takes participants to determine the exact location of a sound and push the necessary button . Below is an example of the directions the participants had to follow.
Additionally, it was found that response times increased in situations in which the sound could originate from speakers symmetrically located in font and in back of the participant, regardless of whether the speakers were positioned on the medial or lateral axis . It was also found that participants were faster to respond to sounds that were located directly in front of them . The following is an example of the response time errors.
Errors, like response time, were influenced by the information content of the stimuli and the location of the stimuli in front and in back of the participant . These results show that auditory warnings can be useful if they are kept simple and that the number of locations the sound can come from is kept to a minimum.
Now that we have learned a little about hearing loss and the problems related to protecting hearing, what do we do next? OSHA’s 1983 amendment said that hearing conservation programs must include noise monitoring, ear protection, education and training, audiometric testing and review and record keeping . All through workers who wear hearing protectors still have hearing loss. Experts attribute this to the employer’s tendency to overprotect employees. At times, management often selects a hearing protector because it has the highest noise reduction rating . If employees can’t hear because they are over protected, they will take out the protectors. Because of this those employees with greater protection are experiencing more hearing loss, and those with less protection have totally effective noise reduction .
Return to Hearing Loss Due to Noise