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The Case of the NOISY WORKPLACE By Mitch Ricketts Math Toolbox is designed to help readers apply STEM principles to everyday safety issues. Many readers may feel apprehensive about math and science. This series employs various communication strategies to make the learning process easier and more accessible.

It has long been known that overexpo- micropascal): is the actual measured in sure to loud may cause , •One (Pa) is about one hun- the environment. The other sound pres- tinnitus (i.e., ringing in the ears) and other dred-thousandth of standard atmo- sure, p0, is a hypothetical reference sound serious health effects (Basner, Babisch, Da- spheric pressure. Standard . In OSH, the reference sound vis, et al., 2014). Hazardous noise levels are pressure is equal to about 14.7 pounds pressure is usually taken to be 20 µPa, or common in many workplaces and the effects per square inch (14.7 psi). This means one alternatively, 0.00002 Pa. This is because on health may surface even among relatively pascal represents a very small pressure of 20 µPa represents the softest sound the av- young workers, as illustrated in Figure 1. about 0.000147 psi (1.47 x 10-4 psi). erage person can distinguish at a range of OSH professionals are often asked to •One micropascal (µPa) is one sound frequencies important to the human identify and control noise hazards. Al- of one pascal, or about 1.47 x 10-10 psi. auditory system. In other words, 20 µPa is though noise control may seem straight- In contrast to the direct measurement of the threshold of hearing, equal to a sound forward, certain concepts are frequently sound pressure in pascals, sound pressure pressure level of 0 . misunderstood. This article explores ter- level (Lp) is an indirect logarithmic mea- In workplaces, sound pressure levels (Lp) minology and calculations to help explain sure based on a ratio of two different sound are normally expressed in units of decibels how sound pressure, sound-pressure level : p and p0. The sound pressure, p, (dB) that reflect increments that and the scale relate to the pressure variations that we call sound. FIGURE 1 WORKPLACE HEARING LOSS, MICHIGAN Sound & Noise Exposure Concepts Noise is sometimes defined as unwanted sound. In air, sound consists of pressure A worker was employed for 13 years in a He also used outdoor power equipment emitted from objects that vibrate noisy assembly plant. at home. or move suddenly. Sound-producing ob- jects include guitar strings, tuning forks, clapping hands, vocal cords, rustling leaves, machinery and explosives. Each passing sound compresses the air, crowding the molecules together. After the wave’s high-pressure band passes, the air rebounds and expands as molecules move apart again. Thus, sound waves can be imagined as repeating cycles of high and low pressure that spread outward from a source (Figure 2, p. 46). Sound waves may also travel as disturbances of matter in His company provided hearing protectors, Before the age of 40, he had developed liquids and solids, such as water and steel. but he rarely wore them. noise-induced hearing loss that was especially severe at higher frequencies. We perceive sound because pressure waves transmit energy, causing vibra- Audiogram Worker age: Late 30s tions in our eardrums, middle ear bones 0

) dB Right ear (ossicles), cochlear fluid and inner ear 20 nerve cells. At moderate sound levels, our 40 auditory systems extract useful informa- tion from sound waves. Unfortunately, 60 nerve damage and hearing loss can occur 80

Hearing loss ( Left ear when sound levels are extreme. 100 Sound pressure (p) is the measurable 0.25 0.5 1 2 3 4 6 8 fluctuation in pressure caused by a sound Frequency (kilohertz, kHz) wave. As shown in Figure 2 (p. 46), sound pressure is reflected in the of a Note. Adapted from “2008 Annual Report on Work-Related Noise-Induced Hearing Loss in Mich- wave. Sound pressure is stated in the inter- igan,” by K.D. Rosenman, A. Krizek, M.J. Reilly, et al., 2009), East Lansing, MI: Michigan State national unit known as the pascal (or more University & Michigan OSHA. commonly, the fractional unit called the

assp.org APRIL 2020 PROFESSIONAL SAFETY PSJ 45 MATH TOOLBOX

can be detected by average people. For quiet FIGURE 2 sounds, people can detect small changes in loudness; however, for loud sounds, only SOUND PRESSURE WAVES large changes are detected. Near the thresh- old of hearing (0 dB), the average person Sound pressure waves are alternating bands of Sound waves can be depicted as curves, with can detect an increase in sound pressure high and low pressure emitted from a source peaks and troughs corresponding to high and of about 2.24 µPa, which represents an in- of sound. low pressure bands. crease of about 1 dB in a very quiet environ- High pressure bands (blue) ment. On the other hand, if the same person is exposed to a sound pressure of 2,000,000 µPa (100 dB), s/he will not detect a change in loudness unless the sound pressure in- creases by about 244,037 µPa (representing Amplitude equals half the difference between an increase of about 1 dB in this noisier minimum and maximum pressure. Larger environment). We will see in the follow- reflect higher sound pressures. ing exercises that an increase of just a few High amplitude Low amplitude decibels in a loud environment represents a serious hazard because the corresponding rise in micropascals is large. In contrast, a small decibel increase is less hazardous in a quiet environment, where the change in Low pressure bands (white) micropascals is small. An important note: OSHA and NIOSH normally express exposure limits as dBA, cals (µPa), or alternatively, pascals (Pa) Step 2. Insert the known values for the which stands for decibels on the A-weight- p = reference sound pressure (thresh- sound pressure measured in the environ- ed scale. Sound pressure levels can be ex- 0 old of hearing; 0 dB); p0 = 20 µPa, or ment (p = 283,000 µPa) and the reference pressed on different frequency-weighting alternatively, 0.00002 Pa sound pressure (p = 20 µPa). Then solve scales. The A-weighted scale emphasizes 0 Note: Be sure to use the same pressure for sound pressure level in decibels (Lp): sound frequencies to which humans are metric (either µPa or Pa) to express vari- most sensitive, while other scales (such ables p and p0 throughout the equation. ,-.,+++ as the C- and Z-weighted scales) do not. " *+ (on the A-weighted scale) 𝐿𝐿 = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙 ,+ = 83.02 𝑑𝑑𝑑𝑑 When monitoring sound pressure levels Calculating Decibels Note: Most calculators have a LOG in the workplace, we normally set our Based on Sound Pressure button that will provide the correct noise meters to the A-weighted scale if we Today’s noise monitoring devices au- answer, with keystrokes similar to the plan to compare our results with exposure tomatically calculate and display sound following in this case: 20 X LOG (283000 limits established by OSHA and NIOSH. pressure levels in decibels (Figure 3). How- ÷ 20) =. Alternatively, in a spreadsheet, In this article, we will calculate decibels ever, it is easier to interpret these numbers the proper formula for this example is based on sound pressures (p) in work- if we understand the calculations. Fur- = 20*LOG10(283000/20). places. In the next Math Toolbox article, thermore, we may be asked to perform the Step 3. Our calculation indicates we will practice other decibel calculations calculations on certification exams. the sound pressure level is 83.02 dB on based on , in per square To begin, imagine a worker’s 8-hour 2 the A-weighted scale (83.02 dBA) as an meter (W/m ). Although these two meth- time-weighted average (TWA) A-weighted 8-hour TWA exposure. ods are based on different characteristics sound pressure exposure is found to be To interpret the measured result, refer of sound, we will obtain the same result in 283,000 µPa. Since our measured sound to the NIOSH recommended exposure decibels regardless of the method we use. pressure is stated in units of µPa, we will limit (REL) of 85 dBA as an 8-hour TWA. use 20 µPa for the reference sound pressure Our calculated daily average noise Sound Pressure Level Equation because this is equivalent to zero decibels. exposure of 83.02 dBA does not exceed To calculate decibels from sound pres- Here is a summary of the information the NIOSH REL of 85 dBA as an 8-hour sure, we may use either micropascals or we will use to calculate the sound pres- TWA. Thus, we conclude that an average pascals as our unit of pressure as long as sure level in decibels: exposure to 83.02 dBA does not trigger we maintain consistency throughout the •The measured A-weighted sound pres- any special NIOSH recommendations. following equation: sure is 283,000 µPa as an 8-hour TWA Alternate example: Calculate the for the worker in this environ- pressure level in decibels for a different envi- 𝑝𝑝 ment. This is the value of p in the formula. ronmental sound level. In this case, imagine 𝐿𝐿" = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙*+ •We are using units of micropascals, so where: 𝑝𝑝+ a worker’s 8-hour TWA A-weighted sound Lp = sound pressure level, in decibels the reference sound pressure is 20 µPa. pressure exposure is 1,124,683 µPa, which (dB) This is the value of p0 in the formula. is equivalent to 1.124683 pascals (Pa). To

log10 = base-10 (i.e., common With this information, we can solve illustrate how to solve the equation in differ- log) the problem as follows: ent units of measurement, first perform the p = actual sound pressure measured in Step 1. Start with the equation for calculations using µPa, then repeat with Pa. the environment (the sound pressure to sound pressure level in decibels: Based on micropascals, insert the mea- which a worker is exposed), in micropas- sured sound pressure (p = 1,124,683 µPa) 𝑝𝑝 46 PSJ PROFESSIONAL SAFETY APRIL 2020 assp.org𝐿𝐿" = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙*+ 𝑝𝑝+ FIGURE 3 ceed the NIOSH-recommended exposure limit (85 dBA)? ENVIRONMENTAL NOISE MONITORING 2) Measured in accordance with the A-weighted scale, a worker’s 8-hour TWA sound pressure exposure is 2.5179 Work area noise measurements with a sound level pascals (Pa). What is the sound pressure

meter (i.e., area monitoring) may misrepresent some level (Lp) in dBA? Since the measured workers’ exposures. Compare this table saw area sound pressure (p) is stated in units of Pa, use 0.00002 Pa as the reference sound exposure of 93.1 dBA with the operator’s personal pressure (p0). Does the result exceed the exposure at bottom. NIOSH-recommended exposure limit (85 dBA)? Calculating Actual Sound Pressure (μPa or Pa) Based on Decibels One of the most practical on-the-job applications of our equation is to con- vert the decibels displayed on a back to actual sound pres- sures. This exercise is useful because it helps us understand the true magnitude of small differences in decibels at noisy work sites. We convert from decibels to actual Dosimeter with a lapel records the sound pressures by rearranging the for- worker’s personal exposure of 97.6 dBA. mula, as follows: Begin with the original formula:

𝑝𝑝 𝐿𝐿" = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙*+ Rearrange the equation 𝑝𝑝to+ solve for p. Keep in mind that we can perform any operation on one side of the equation as long as we perform that same operation on the other side. Let’s begin by dividing both sides of the equation by 20:

𝑝𝑝 𝐿𝐿" ÷ 20 = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙+, ÷ 20 Next, cancel the 20 where𝑝𝑝, you can:

Photos by Becky Ricketts 𝑝𝑝 𝐿𝐿" ÷ 20 = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙+, ÷ 20 Simplify by eliminating𝑝𝑝 the, canceled terms: and reference sound pressure (p0 = 20 does exceed the NIOSH REL of 85 dBA. µPa) to obtain the following result: This means the worker faces an increased 𝑝𝑝 𝐿𝐿" ÷ 20 = 𝑙𝑙𝑙𝑙𝑙𝑙*+ risk of noise-induced hearing loss, and 𝑝𝑝+ we must implement the corresponding Continue rearranging by taking the " *+ 1,124,683 (on the A-weighted scale) inverse logarithm (antilogarithm) of each 𝐿𝐿 = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙 = 95 𝑑𝑑𝑑𝑑 NIOSH recommendations. 20 To solve the same problem based on side of the equation: pascals, we insert 1.124683 Pa for the You Do the Math 1 measured sound pressure (p) and .00002 Apply your knowledge to the following % +,-./0 2 Cancel where#$ ÷ '(you) can: 10 Pa for the reference sound pressure (p0): questions. Answers are on p. 55. 10 = 10 1) Measured in accordance with the 1 +,-./0 2 A-weighted scale, a worker’s 8-hour #$%÷'() 10 " *+ 1.124683 (on the A-weighted scale) Simplify: 𝐿𝐿 = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙 = 95 𝑑𝑑𝑑𝑑 TWA sound pressure exposure is 632,456 10 = 10 0.00002 Both calculations result in an average micropascals (µPa). What is the sound #$%÷'() 𝑝𝑝 sound pressure level of 95 dBA for the pressure level (Lp) in dBA? Since the Multiply both10 sides by= p( : worker in this environment. Since the measured sound pressure (p) is stated in 𝑝𝑝 0 example states that the exposure was units of µPa, use 20 µPa as the reference measured as an 8-hour TWA, the result sound pressure (p0). Does the result ex- #$%÷'() ( 𝑝𝑝 ( 10 × 𝑝𝑝 = ( × 𝑝𝑝 assp.org APRIL 2020 PROFESSIONAL SAFETY𝑝𝑝 PSJ 47 MATH TOOLBOX

Cancel where you can: The result indicates that the sound pres- All concepts have been defined in the sure level of 98 dBA equals an actual sound text, formulas and illustrations. Answers pressure of 1,588,656.47 µPa (approxi- are on p. 55. #$%÷'() ( 𝑝𝑝 ( mately 1,600,000 µPa, which equals nearly 10 × 𝑝𝑝 = ( × 𝑝𝑝 Concepts Simplify: 𝑝𝑝 1.6 Pa). Compare this sound pressure with 7) decibel (dB) the previous example’s result of approx- 8) micropascal µPa) imately 800,000 µPa (0.8 Pa) for 92 dBA. #$%÷'() 9) pascal (Pa) Rearrange,10 and use× the𝑝𝑝( = resulting𝑝𝑝 equa- Taken together, these results illustrate 10) reference sound pressure (p0) tion to solve for p: an important aspect of the decibel scale, 11) sound pressure (p, p ) namely, at high sound pressure levels, even 0 12) sound pressure level (L ) a small increase in decibels can represent a p %&'÷)*+ 13) sound waves Imagine that𝑝𝑝 = monitoring10 × indicates𝑝𝑝* a dramatic increase in sound pressure. worker’s 8-hour TWA noise exposure is Definitions (in random order) 92 dB on the A-weighted scale (92 dBA). You Do the Math a) A direct measure of the pressure What is the sound pressure in micropascals? Answers are on p. 55. fluctuation caused by a sound wave in Step 1. Start with the sound pressure 3) Imagine that monitoring indicates µPa or Pa. level equation, modified to solve for p: a worker’s 8-hour TWA noise exposure b) Threshold of hearing (0 dB; the soft- is 104 dBA, an increase of 6 dB from the est sound the average person can hear). previous example. What is the new sound This value equals 20 µPa, or 0.00002 Pa. %&'÷)*+ where: * pressure in micropascals? Use 20 µPa as c) International unit of pressure that 𝑝𝑝 = 10 × 𝑝𝑝 -4 p = actual sound pressure measured in the reference sound pressure, p0, since the equals about 0.000147 psi (1.47 x 10 psi). the environment (the sound pressure to question asks for micropascals. d) International unit of pressure that which a worker is exposed), micropascals 4) Imagine that monitoring indicates equals about 1.47 x 10-10 psi. (µPa), or alternatively, pascals (Pa) a worker’s 8-hour TWA noise exposure e) Unit of measure for sound pressure is 84 dBA, a decrease of 20 dB from the levels, reflecting differences in loudness Lp = sound pressure level, decibels (dB) example in Question 3. Again, use 20 µPa that can be detected by average people. p0 = reference sound pressure (thresh- as the reference sound pressure, p , to f) Alternating bands of high and low old of hearing; 0 dB); p0 = 20 µPa, or 0 alternatively, 0.00002 Pa calculate micropascals. What is the new pressure spreading outward from an ob- Step 2. Insert the known values for sound pressure? ject that vibrates or moves suddenly. g) Indirect measure of sound ex- sound pressure level in decibels (Lp = 92 dBA) and reference sound pressure (use How Much Have I Learned? pressed in decibels. Try these problems on your own. An- p0 = 20 µPa because the question asks for micropascals). Solve for sound pressure swers are on p. 55. For Further Study measured in the environment (p): 5) Measured in accordance with the Learn more from the following sources: A-weighted scale, a worker’s 8-hour •ASSP’s ASP Examination Prep: Pro- TWA sound pressure exposure is 399,052 gram Review and Exam Preparation, (&'÷')) 𝑝𝑝Note:= 10 Check your× 20 =calculator’s796,214.34 user 𝜇𝜇𝜇𝜇𝜇𝜇 micropascals (µPa). What is the sound edited by Joel M. Haight, 2016. manual for instructions on raising 10 pressure level (Lp) in dBA? Since the •OSHA Technical Manual (TED 01- to a power, as required for the equation. measured sound pressure (p) is stated in 00-015), Section III, Chapter 5: Noise, by Most calculators have a button such as units of µPa, use 20 µPa as the reference OSHA, 2013; www.osha.gov/dts/osta/ INV, 10X, ^ or similar for this purpose. sound pressure (p0). otm/new_noise/index.html. In Excel, the formula for this example is 6) Imagine a worker’s 8-hour TWA •Criteria for a Recommended Stan- = (10^(92/20))*20. noise exposure is 112 dBA. What is the dard: Occupational Noise Exposure (Re- Step 3. The result indicates a sound sound pressure in pascals (Pa)? The vised Criteria), by NIOSH, 1998; www pressure level of 92 dBA equals an actual question asks for the result in pascals, .cdc.gov/niosh/docs/98-126/pdfs/ sound pressure of 796,214.34 µPa (ap- so use 0.00002 Pa as the reference sound 98-126.pdf. PSJ proximately 800,000 µPa, which equals pressure (p0). about 0.8 Pa). References Basner, M., Babisch, W., Davis, A., et al. Alternate example: Imagine that The Language of Sound Pressure Levels (2014). Auditory and non-auditory effects of monitoring indicates a worker’s 8-hour noise on health. Lancet, 383(9925), 1325-1332. TWA noise exposure is 98 dBA, an in- Readers will encounter the following Rosenman, K.D., Krizek, A., Reilly, M.J., et crease of 6 dB from the previous exam- concepts in codes, certification exams al. (2009). 2008 Annual report on work-related ple. What is the new sound pressure in and conversations with other profession- noise-induced hearing loss in Michigan. East micropascals? Again, the question asks als. Match the numbered concepts with Lansing, MI: Michigan State University and for the result in micropascals, so use 20 their paraphrased definitions (lettered). Michigan OSHA.

µPa as the reference sound pressure (p0). Insert the known values for the new Mitch Ricketts, Ph.D., CSP, is an associate professor of safety management at Northeastern State University (NSU) in Tahlequah, OK. He has worked in OSH since 1992, with experience in diverse settings sound pressure level in decibels (Lp = 98 such as agriculture, manufacturing, chemical/biological laboratories and school safety. Ricketts holds dBA) and reference sound pressure (p0 = 20 µPa). Solve for sound pressure mea- a Ph.D. in Cognitive and Human Factors Psychology from Kansas State University, an M.S. in Occupa- sured in the environment (p): tional Safety Management from University of Central Missouri, and a B.S. in Education from Pittsburg State University. He is a professional member and officer of ASSP’s Tulsa Chapter, and faculty advisor for the Society’s NSU Broken Arrow Student Section. (&'÷)*) 48𝑝𝑝 = PSJ10 PROFESSIONAL× 20 = 1,588,656 SAFETY.47 𝜇𝜇𝜇𝜇𝜇𝜇 APRIL 2020 assp.org If the day feels like an off day, the feeling that things are not quite right should equate to a large yellow caution sign

in your mind. IMAGES BERTLMANN/E+/GETTY have personal issues, the feeling that things potential for human error would certain- Floyd, A.H.L. & Floyd, H.L. (2013). Cultural are not quite right should equate to a large ly reduce the number of workplace inju- drift and the occlusion of electrical safety. IEEE yellow caution sign in your mind. ries in the U.S. PSJ Transactions on Industry Applications, 50(3), Consider the safety impact of your 1610-1618. doi:10.1109/TIA.2013.2288431 actions, not only on yourself, but also on References Manuele, F.A. (2013, May). Preventing seri- ous injuries and fatalities: Time for a sociotech- coworkers and other people in the area. Bureau of Labor Statistics (BLS). (2019a, Dec. 17). Census of fatal occupational injuries: nical model for an operational risk management Two OSHA records describe incidents system. Professional Safety, 58(5), 51-59. in which workers were electrocuted while Archived data. Retrieved from www.bls.gov/ iif/oshcfoiarchive.htm#rates Mendeloff, J. & Staetsky, L. (2014). Occu- they were attempting to fix equipment BLS. (2019b, Dec. 17). Current population sur- pational fatality risks in the U.S. and the U.K. and another worker saw a circuit breaker vey, census of fatal occupational injuries. Retrieved American Journal of Industrial Medicine, 57, 4-14. turned to the off position and reset it from www.bls.gov/news.release/pdf/cfoi.pdf Retrieved from https://pdfs.semanticscholar.org/ (which is why we have lockout/tagout BLS. (2020). Occupational injuries/illness- b45c/277204ffeac428f84c1a125c476164 d7f907.pdf procedures) (OSHA, 2012; 2017). Power es and fatal injuries profiles. Retrieved from OSHA. (2012, Sept. 12). Accident line incidents on construction sites often https://data.bls.gov/gqt/ProfileData 202570073: Worker electrocuted while fixing Dekker, S.W.A. (2000). Field guide to human a smoke machine [Accident report detail]. Re- kill or severely injure workers who are trieved from www.osha.gov/pls/imis/accident not responsible for the contact. error [Draft]. Bedford, U.K.: Cranfield Press. Domitrovich, T.A., Floyd, A. & Smail, T. search.accident_detail?id=202570073 In my incident at the store, the worker OSHA. (2015, Mar.). Accident 75228.015: who dangerously propped up the map (2012). Methods to influence change in home safety. Conference record of the 2012 IEEE IAS Employee is electrocuted while testing trans- stand was not thinking of the safety of Electrical Safety Workshop, Daytona Beach, FL, former [Accident report detail]. Retrieved others. The worker was likely inexperi- 1-8. doi:10.1109/ESW.2012.6165534 from www.osha.gov/pls/imis/accidentsearch enced and trained to keep everything Floyd, A.H.L. (2012). Multitasking and .accident_detail?id=75228.015 in the store in its proper place. The map the illusion of safety: The potential impact OSHA. (2017, June 18). Accident 96429.015: stand was broken and should have been in certain electrical hazard scenarios. IEEE Employee is electrocuted [Accident report removed. Not only did I err in judgment, Industry Applications Magazine, 18(3), 18-22. detail]. Retrieved from www.osha.gov/pls/imis/ accidentsearch.accident_detail?id=96429.015 but the store worker (i.e., administrative doi:10.1109/MIAS.2012.2185999 control) also erred and, in doing so, cre- Tammy Gammon, Ph.D., P.E., is a senior electrical engineer for John Matthews and Associates, ated an unsafe environment. a consulting electrical engineering firm that specializes in electrical power systems, fires of electrical My knee injury is a daily reminder that origin, and electrical arc and shock injuries. She is the former research manager for the IEEE/NFPA Arc mistakes are part of the human experi- Flash Research Project. Gammon is the author of many articles on electrical safety, electrical injuries ence. The best way to prevent a workplace and arc-flash hazards. She holds a Ph.D. in Electrical Engineering from Georgia Institute of Technology. injury or fatality is to remove potential Gammon is a professional member of ASSP’s Georgia Chapter. human error from the equation. In the U.S. and in many countries around the world, workplaces have made Math Toolbox, continued from pp. 45-48 great strides in training workers, develop- ing safer work practices and creating safer 3) Answers: The Case of (&'(÷*') workplaces. In 1992, 2003 and 2017, U.S. the Noisy Workplace 𝑝𝑝 = 10 × 20 = 3,169,786.39 𝜇𝜇𝜇𝜇𝜇𝜇 fatal occupational injury rates were 5, 4 You Do the Math 4) and 3.5 per 100,000 workers, respectively (&'÷)*) Your answers may vary slightly due to 𝑝𝑝 = 10 × 20 = 316,978.64 𝜇𝜇𝜇𝜇𝜇𝜇 (BLS, 2019a;b); these rates are much lower rounding. than the 1971 U.S. worker fatality rate of How Much Have I Learned? 17.1 (Manuele, 2013). As shown in Figure 1) 5) 1, the number of fatal worker injuries " *+ 632,456 399,052 has not consistently declined since 2009. 𝐿𝐿 = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙 = 90 𝑑𝑑𝑑𝑑 𝐿𝐿" = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙*+ = 86 𝑑𝑑𝑑𝑑𝑑𝑑 If the worker is exposed20 8 hours per 6) 20 Mendeloff and Staetsky (2014) found day, 40 hours per week, this A-weighted (&&'÷')) that the U.K. (as well as several other result exceeds the NIOSH recommended If you𝑝𝑝 = calculated10 ×the0. 00002answer= as7 .96 𝑃𝑃𝑃𝑃 European countries) has fatal overall and exposure limit of 85 dBA. 7,962,143.41, remember the question asked electrical injury rates of about one-third for pascals, rather than micropascals. and one-quarter of those in the U.S.; 2) they attribute the lower rates to high-lev- 2.5179 The Language of 𝐿𝐿" = 20 ∙ 𝑙𝑙𝑙𝑙𝑙𝑙*+ = 102 𝑑𝑑𝑑𝑑𝑑𝑑 el-management focus on safety issues and If the worker is exposed0.00002 8 hours per Sound Pressure Levels in-house risk assessments. day, 40 hours per week, this A-weighted 7) e; 8) d; 9) c; 10) b; 11) a; 12) g; 13) f. Even well-trained workers can make result exceeds the NIOSH recommended mistakes. Identifying and removing the exposure limit.

assp.org APRIL 2020 PROFESSIONAL SAFETY PSJ 55