Audiometric Testing is more than just a simple hearing test. When multiple years’ worth of test results are considered against each other, a detailed picture of an employee’s hearing will emerge. These results can indicate that an injury has already occurred or provide an early warning allowing employers and employees to identify safety problems and remedy them before a recordable injury occurs.
But what are the tests actually measuring?
Why does OSHA focus on only three frequencies?
How are the test results translated?
When does a shift become recordable?
These are just some of the questions that employers and employees might have regarding Audiometric Tests. Here is a breakdown of what Audiometric Tests look for and how that information is used to protect employees’ hearing and determine which injuries are recordable on a company’s OSHA 300 Log.
The Range Being Tested
OSHA is primarily interested in three frequencies: 2,000 Hz, 3,000 Hz and 4,000 Hz. OSHA has singled these frequencies out in particular because they span the range that includes the vast majority of industrial noises. If injuries to an employee’s hearing are workplace-related, then these are the frequencies that will most likely be affected.
However, 2,000 Hz to 4,000 Hz represents a relatively small segment of the total range of human hearing. Accordingly, OMY voluntarily tests a range of 500 Hz to 8,000 Hz to provide a clearer picture of what the employee is actually hearing. Additionally, the expanded range can serve as an early-warning system to identify hearing impairment and take action to remedy the situation before it ever reaches the level of a recordable injury.
Decibels vs. Hertz
OSHA regulates the number of decibels that an employee can be exposed to over a set amount of time, which they call the Time-Weighted Average (TWA). However, Audiometric Testing focuses on the ability of the employee to hear specific frequencies measured in Hertz. So what is the relationship between decibels and Hertz?
The decibel level refers to the noise level – or volume – that an employee is exposed to in the workplace. Employees working in environments where the TWA is over 85 dBs should be wearing hearing protection. Exposing employees to damaging decibels without proper protection can result in citations even if there are no recordable shifts. Exposure to decibels at or beyond this level can damage the employee’s hearing, which will be evident by difficulty hearing specific frequencies – or pitches – during Audiometric Testing. These difficulties can indicate that an injury has occurred. Additionally, the Audiometric Test will identify the employee’s ability to hear those frequencies at different volumes, so here again, we see an interplay of frequencies and decibels.
When an OMY Audiometric Test indicates that an employee is having difficulty hearing OSHA’s targeted frequencies – possibly due to exposure to high decibels – it might indicate that an injury has occurred. However, we need a little more information before we can say for sure.
Audiometric Test Results are Measured on a Scale
Audiometric Tests measure an employee’s ability to hear specific frequencies at multiple decibel ranges (pitches at varying volumes), but we can then take those test results and place them on a scale that runs from 0 to 100 in decibel increments of five.
On this scale, zero represents the “best” hearing and 100, the “worst.” A result of 100 would register, in essence, as non-responsive.
This number tells us how well the employee can hear now, but in order to identify if an injury has occurred, we need to compare it to previous years to identify any changes or shifts.
Audiometric Test Results are Compared to a Baseline Recording
A single Audiometric Test can provide a clear picture of how “good” or “bad” a person’s hearing is (barring an outside health complication), but determining whether or not an injury has occurred requires the test results to be compared against an employee’s baseline reading.
Audiometric Tests are administered annually, so the first one serves as the baseline reading while each subsequent test helps to fill in a picture of the employee’s hearing over time. Theoretically, with enough results from enough employees, we can work backwards to identify safety trends within departments throughout the workplace. For example, if a large percentage of employees show drastic changes over the same period of time, then the employer can make an effort to identify what might have caused the change and reexamine their approach to hearing safety accordingly.
Once we have multiple tests to examine, we can identify changes or shifts that have occurred over the arc of an employee’s career, but OSHA is particularly interested in shifts affecting the predetermined frequencies that are of a certain severity.
Standard Threshold Shifts vs. Recordable Standard Threshold Shifts
Once changes have been identified by comparing them to baseline test results, there are two primary categories that we are interested in: Standard Threshold Shifts (STS) and Recordable Standard Threshold Shifts.
An employee who has experienced a change of more than 10 dBs from their baseline is said to have experienced a Standard Threshold Shift. This is cause for concern, but it does not formally indicate that an injury has occurred. However, once they hit greater than 25 dBs from their baseline, the injury becomes a Recordable Standard Threshold Shift. Keep in mind that when we’re talking about shifts and recordable shifts, we are only focusing on the 2,000, 3,000 and 4,000 Hz frequencies that OSHA is concerned with.
Once a recordable shift has been identified, a follow-up retest is performed within 30 days to confirm the shift. At this point in the process, the employee has indicated a shift of at least 25 dBs on the targeted frequencies, which has been confirmed in a retest, and the employer will have to list the injury on their OSHA Log or do a Workplace Determination.
Recordable Shifts aren’t Automatically Workplace-Related
By the time a recordable shift has been confirmed, there is no doubt that the employee has suffered hearing loss. However, there are many factors that can contribute to hearing loss both on and off the job. During a Workplace Determination, a physician/audiologist will examine the employee’s Audiometric Testing records and inquire into their listening behaviors to determine if the injury is attributable to the workplace.
Because the employees use the same ears (and lungs, hands, backs, etc.) at work as they do at home, it can be difficult to determine with confidence who is responsible for the employee’s injury. Hearing loss can be caused by a wide range of factors depending on the employee’s exposure to sounds, and in some cases, it can simply be attributed to the aging process.
Additionally, Workplace Determinations can be appealed if new information emerges that wasn’t considered during the initial determination. Items can even be retroactively removed from the OSHA 300 Log.
OMY’s Audiometric Testing covers the range of 500 – 8,000 Hz, which is well beyond the three frequencies (2,000 Hz, 3,000 Hz and 4,000 Hz) that OSHA takes into consideration. The results are analyzed on a scale of 0 to 100 where 0 is “best” and 100 is “worst.” A shift of 10 dB on these frequencies indicates that a shift has occurred, but only shifts of 25 dB or more are recordable. Once a recordable shift has been confirmed, an employer can either perform a Workplace Determination or list the injury on their OSHA 300 Log.
Additionally, as a mobile medical testing company, OMY can perform Audiometric Tests at your site, which drastically reduces costs due to downtime that are incurred by sending employees offsite. The results are delivered on an easily storable and searchable flash drive for future reference. Contact us today to tell us about your testing needs and get a quote.
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