NOISE SURVEY. EQUIPMENT: Sound Level Meter Octave Band Analyzer Dosimeters Sound Calibrator Survey Sheets Tape measure SP 10

Transcription

1 SP 10 HSCI 348 Industrial Hygiene Instrumentation Techniques Laboratory No. 10 NOISE SURVEY OBJECTIVES Upon completion of this laboratory, the student should: 1) be familiar with the use of noise dosimeters and the comparison of results with SLM's and OBA's. 2) be introduced to the real world of sampling people. 3) be familiar with conducting a real-world IH survey, specifically here for noise 4) be familiar with noise mapping EQUIPMENT: Sound Level Meter Octave Band Analyzer Dosimeters Sound Calibrator Survey Sheets Tape measure

2 PROCEDURE Part 1. Familiarization With Data Forms 1) Become familiar with the data collection forms to be used in this lab (see Supplemental Data Forms in the Lab Suppporting Information section of the class website). Although you will not be able to complete all the information on these forms, you will find them useful for data recording during the lab. 2) To be recorded are such items as: subject name, job title and duties, location, times, date, surveyed by, calibration, instrumentation specifications, and your data. Also included are some subjective questions regarding subject's use of hearing protection, cooperation, suspicion of tampering, any unusual circumstances, etc. Part 2. Calibration and Setting of Instruments 1) Before beginning the survey, calibrate the instruments with the sound calibrator and record your results. 2) Set the parameters for the dosimeter settings in the Quest Noise Pro as follows: - Hearing Conservation Amendment (criteria 90, threshold 80, doubling rate 5) - PEL (criteria 90, threshold 90, doubling rate 5) - TLV (criteria 85, threshold 80, doubling rate 3) - optional fourth dosimeter in NoisePro Part 3. Worker Exposure Sampling with Dosimeters 1) The noise survey will be conducted by observing and sampling workers at the Purdue Printing Plant. 2) After being assigned a worker, your group should explain the purpose of the survey to him/her, attach the dosimeter (on belt, with microphone on shoulder) and collect readings for a minimum of 60 min (or longer, if possible). 3) Be sure to note break times. Also, find out from the worker if the sample period will likely be representative of the rest of his day. Part 4. Noise Survey with SLM 1) After the dosimeters are started, conduct a time-motion study. Collect SLM (A-weighted) readings with a Type 2 SLM at positions around the sound source/worker location in order to develop a noise map. To do this properly and to be able to develop the noise map, you will need to establish a grid pattern to determine where to take readings. In addition, add any additional positions to be sure you are obtaining readings where the worker spends significant blocks of time. Approximate (in 5 to 10 minute blocks) the total amount of time the worker is at each of these locations. 2) Diagram the work station layout, sampling positions and noise levels at each position. 2

3 3) Take background readings when the main noise source (the operation to which your worker is assigned) is not operating. 4) As applicable, if there are any noise control devices available (e.g., barriers, etc.), test their effectiveness, by taking readings with and without the controls. Part 5. Frequency Analysis with OBA Perform a frequency analysis at the main worker position while the machine is running and at an appropriate time for background. Part 6. Completion of Survey 1) Collect your dosimeter from your worker. Be sure to thank him/her for his/her cooperation. 2) Read and record the doses from the dosimeter. 3) Post-calibrate your instruments. RESULTS: 1. Complete all applicable parts of the attached data forms, including calibration data. 2. Prepare a table comparing the dosimeter results. Remember that you will actually have three results from the dosimeter (PEL-HCA, PEL, TLV). 3. Based on the dosimeter results, determine the worker s L avg sound level.for the time sampled. 4. Based on the SLM noise survey (time-motion study), determine the worker s L avg sound level 5. Calculate the worker s 8-hr TWA to determine if the worker is in compliance with the OSHA standards, using your best estimate of the L avg from the dosimeters and the SLM timemotion study. Assume that his work conditions are at the same level for the rest of the day, unless you have information provided to you by the worker about plans for the rest of his work day. Use the worker s actual shift time and break times for this calculation. 6. Calculate the worker s 8-hr TWA to determine if the worker is in compliance with the TLV. 7. Plot the frequency distributions (source and background), with db on the y-axis and frequencies (equally spaced) on the x-axis. 8. Draw a noise map of the area around your worker s work area and sound source, using the grid pattern developed to take your SLM noise data. Draw equal sound level contours with your data. DISCUSSION: 1. Briefly describe your worker s noise sources and the surrounding work environment. In general, would you describe the noise as continuous, intermittent or impact? 3

4 2. How did the background noise level compare to the worker s main noise source? Did it contribute significantly to his overall exposure? 3. What was the worker s noise exposure and for what exposure time (based on the dosimeters and the SLM survey)? Based on your estimate for the exposure during the entire work day, was your worker in compliance with the OSHA noise standard, (PEL and HCA)? With the ACGIH TLV? 4. How did the dosimeter measurements compare with the SLM readings? What might be the cause of any differences seen between these two types of measurements? 5. What were the predominant frequencies of the noise source and of the background? By looking at the noise spectrum, could there be damaging auditory effects? 6. If there were any control devices, how effective were they? CONCLUSIONS: For this lab report your conclusions should be incorporated into an executive letter summary. Write a one to two page letter addressed to Ms. Cheryl Purefoy, the Director of Printing Services, Purdue University, summarizing your findings and results. Approach this letter as if you are an industrial hygiene consultant and she is your client. Also include any recommendations you might have. 4

5 Introduction The purpose of this lab was to become more familiar with the sound level meter, octave band analyzer, and the dosimeter. We also developed a better understanding of how the properly survey a work situation and fill out corresponding forms. The purpose of Part 1 was used to familiarize the data forms. These forms were to be used while we sampled the work environment. In Part 2 of the lab we calibrated the instruments with the sound calibrator (1kHz and 114 db). The results were then recorded. The third part of the lab involved the actual surveying of the printing plant worker. The consisted of doing noise sampling and observing his work environment and job duties. We were assigned a worker. We attached a dosimeter to him and explained the purpose of the survey. The reading were recorded for a minimum of 60 minutes and then later recorded. After we attached the dosimeters to our worker, we then proceeded with the fourth part of the lab. In Part 4 we diagramed the work station layout in order to create our grid pattern. This grid pattern was used to note the sampling positions and noise levels at each position. We also took noise level readings around control devices to test their effectiveness. In part 5 we took an OBA reading at the main worker position while the machine was running. Finally in the last part (part 6), we collected our dosimeter from our assigned worker and recorded the doses. Then we finished the lab with a post calibration with the sound calibrators. The pictures below are: (1) folding machine where we did our noise sampling and (2) The worker (Lyle) doing his job with the dosimeters in place. (1) (2) 5

6 Results **The applicable parts of the forms from part 1 are attached. Table 1. Dosimeter Results and calculated L avg Percent of TWA (Dose) L avg (dba) * OSHA - PEL.102% OSHA - HCA 3.678% ACGIH TLV** 7.047% *L avg = log (D), where D= (dose/12.5*t) T= 1hr and 1 min= approx **L eq is the equivalent to L avg Equations Used to Calculate L avg : OSHA log(D) and ACGIH log(D) Sample calculation using OSHA-PEL: log (.00803) = Table 2. SLM Results and Calculated L avg Location of worker/ Duty Mid machine (button operation) Front of machine (load paper) Back of machine (collect folded paper) Lp w/ lid (dba) Lp w/o lid (dba) Estimated Exposure Time (min) 6 Allowable Exposure Time OSHA (hours)** Allowable Exposure Time TLV (hours)** min min min *L avg for an hour: OSHA dba TLV dba *L avg = TWA (OSHA)= log (D% / 12.5 *1) or TWA (TLV)= 85+10log (D% / 12.5*1) ** Allowable Exposure time: T(hr)= 480/(2 (L-Std)/ER ) Sample calculation for TWA (OSHA): *D= actual/allowed, Total D for an hour: D 1 +D 2 +D 3. D= (20min/[480/(2 ( )/5 )] )+(40min/[480/(2 ( )/5 )] )=.0423 TWA (OSHA)= log (4.23/12.5*1) **Allowable Exposure Time using the Lp w/ lid OSHA TLV T = 480/(2 ( )/5 ) T= 480/ (2 ( )/3 ) T= T= *** For calculation purposes the L avg for with the lid was used in the lab report.

7 Table 3. Worker s 8 hr TWAs for OSHA Meter Used L avg (dba) TWA (dba) * Dosimeter: OSHA HCA SLM *The worker worked 8 hours and had a 30min break (assumed to be <80db) This information is used to calculate the worker s TWA. The dose for OSHA PEL was not included in the table due to it being so low of a value. Equations used: TWA= logD D= D% /(12.5*7.5) Sample equation: D=3.7/12.5*7.5=.0395 TWA= log(.0395)= Table 4. Worker s 8 hr TWAs for ACGIH Meter Used L avg (dba) TWA (dba) * Dosimeter: ACGIH TLV SLM *The worker worked 8 hours and had a 30min break (assumed to be <80db) This information is used to calculate the worker s TWA. Equations used: TWA= logD D= D% /(12.5*7.5) Sample equation: TWA= log (.0752)= D=7.05/12.5*7.5=

8 db HSCI 348L SP 10 Figure 1. Comparison of Frequency vs. db collected (source and background) Frequency Distributions for the Source and the Background frequencies (Hz) Source Background The above plot shows the frequency distributions (source and background), with db on the y-axis and frequencies (equally spaced) on the x-axis. 8

9 Discussion 1. The folding machine was the source of noise for our worker. This particular machine created a continuous noise until it ran out of paper to fold. The surrounding noise was produced by the other machines located in the printing plant. These machines also created a continuous noise until it was shut off. 2. The background noise sample from the printing plant was 70.1 db. The noise samples taken by the worker s main noise source was calculated to have a L avg of based on the criteria for OSHA and based on the criteria for the ACGIH. The background noise is not contributing to the noise levels since is not within 10 db of the calculated L avg. 3. We recorded the workers noise exposure for an hour and 1 min. Based on the dosimeter readings for OSHA HCA (81.06 dba) and ACGIH TLV (85.75 dba), and the SLM readings based on the OSHA and ACGIH criteria ( and dba respectively), our estimates for the noise exposure during the entire work day show that the noise levels were below the criterion levels for OSHA (90dB) and higher than the criterion level set forth by the ACGIH (85 db). They were also above the threshold levels set in place in by ACGIH (80dB) and OSHA (80 db). So even though they are in compliance with OSHA, the worker still may be at risk for hearing loss especially since the noise levels exceeded the ACGIH noise level. 4. The SLM meter measured the sound level around the machine. The dosimeter measures the amount of dose the worker is subject too. In the printing press the SLM had a similar dba of dba to the dosimeters which had a calculated dba of OSHA HCA (81.06) and ACGIH TLV (85.75). We believe the dosimeter reading for OSHA PEL (55.19) would have been similar also if it wasn t placed on the workers left side. This is due to the fact that the worker is right handed so he tends to lean his right side in more while doing his job. This causes his left side to be further away from the source. 5. Based on the SLM data and the data taken from the OBA data, we received two contradicting answers. However based on the OBA data, the dominant frequencies were 500, 1000, 2000, 4000, and 8000 Hz for the source and 2000 and 4000 for the background. This is important because the frequencies for speech and hearing are between Hz. The highest dba level, 87.7dB at 2000 Hz was found while the machine was running. This is under the criterion level but there is a risk of hearing damage and ear protection should be worn. 6. There was a damper device on the machine. It was a lid, located at the end of the machine. When it was lowered the sound level was decreased significantly. The sound level with the lid up was 92.5 db and the sound level with the lid down was 82.5 db. This was a 10% difference. The percent difference was calculated by the following equation: (10^8.25/10^9.25)*100=10% left of the original sound level. This tells us that there was a 90% difference. Conclusion See Next Page 9

10 Ms. Cheryl Purefoy Director of Printing Services Purdue University Dear Ms. Cheryl Purefoy, We conducted a sound level study at the Printing Press on April, 15 th, During our study we took sound readings for an hour and focused mainly on the surrounding area of the folding machine located in the back of the building. While conducting our sound level sampling at the folding machine we found that the worker assigned to the machine is exposed to a TWA of dba (according to OSHA Hearing Conservation Amendment), dba (according to ACGIH Threshold Limit Value), and and dba (according to the Sound Level Meter). These TWAs are based on his 7.5 hours of work (assuming he has a 30 minute break that is <80dB). According to the data from the survey the worker was compliance with the regulations and standards set in place by the ACGIH. The regulations set by the ACGIH takes into account the possibility of the employee developing hearing loss at lower levels of sound. Since the sound levels do not exceed the regulations and standards set in place by the ACGIH we suggest that the employee isn t required to wear hearing protection. However we suggest he should wear ear plugs in order to ensure hearing protection around the machine because there is the possibility that other machines located in the building may add to the total sound level causing it to become higher and more of a risk for the employee. Sincerely, Matt Smith Anicia Howard Emily Gerig 10