한국소음진동공학회논문집제 2 권제 8 호, pp. 742~752, 21. DOI : 1.55/KSNVE.21.2.8.742 가청화를이용한고소음작업장의흡음대책평가 Evaluation on Attenuation for Sound-absorbing Measures of Loud Noisy Work-site using Auralizational Technique 윤재현 * 김재수 Jae-Hyun Yun and Jae-Soo Kim (21 년 6 월 1 일접수 ; 21 년 7 월 29 일심사완료 ) Key Words : Sound-absorption Measure( 흡음대책 ), Acoustic Simulation( 음향시뮬레이션 ), Auralization( 가청화 ), Psycho-acoustics Experiment( 청감실험 ) ABSTRACT In case of the working machine that using in the loud-noisy, as it generates the loud-noise, it is influencing a physical, mental bad effect to those workers. Accordingly, though the noise countermeasure for the loud-noisy is acutely requiring, until now, those methods that wearing the soundproof-protection tool, or restriction the working hours, and minimize the noise exposure volume, were mainly used. However, such noise countermeasures occur many problem points. On such point of view, using the acoustic simulation technique, let the workers to choose the where suffering many damages due to the noise of working machine, and after grasp the physical property of working machine and indoor acoustic characteristic, this Study has attempted to grasp the reduction degree of noise level at before-improvement after-improvement, through the sound-absorption measure. Passing through such preceding step, using auralizational technique based on the noise of working machine of before-improvement after-improvement, and by conduct psycho-acoustics evaluation, this study intended to investigate the change degree of subject reaction. As the result of evaluation, it is considering that the noise-reduction countermeasure method for the loud-noisy could be much effective, through the sound-absorption measure. * 1. 서론 산업혁명이후다양한작업기계가발명되면서노동력과시간을줄일수있게되었다. 그러나고소음작업장에서사용하는작업기계의경우고소음을발생시켜작업자들에게신체적, 정신적악영향을미치고있다. 따라서고소음작업장의소음대책이절실 교신저자 ; 정회원, 원광대학교건축공학과 E-mail : soundpro@wonkwang.ac.kr Tel : (63)85-5712, Fax : (63)843-782 * 정회원, 원광대학교건축음향연구실 히필요하나지금까지는방음보호구를착용하거나작업시간을제한하여소음노출량을최소화하는방법을주로사용하였다. 그러나이러한소음대책은소극적이고영구적이지않으므로많은한계를가지고있으며, 또한작업자에게보호구착용으로인한불편함과작업시간제한에따른생산성저하를초래하는등의문제를발생시킨다. 이러한관점에서이연구는음향시뮬레이션기법을이용 (1) 하여작업자로하여금작업기계의소음으로인하여많은피해를받고있는작업장 ( 보석가공장, 모형공작실 ) 을선정하여, 현재사용하고있는작업기계의물리 742/ 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년
가청화를이용한고소음작업장의흡음대책평가 적특성을파악하였다. 또한시뮬레이션과의신뢰성확보를위해실내음향상태를측정한뒤동일한음향상태를갖는작업장을모델링한후흡음대책을통해개선전 후의소음레벨저감정도를파악하고자하였다. 이러한선행단계를거쳐가청화기법을이용하여개선전 후의작업기계소음을바탕으로청감평가를실시하여주관적반응변화정도를조사 (5) 하고자하였다. 이러한자료는연구대상고소음작업장과유사한작업장의소음저감대책시유용한자료로활용될수있을것으로사료된다. 2. 개요및측정방법 2.1 연구대상고소음작업장의개요측정대상작업장제원및마감재료의주파수별 흡음률은 Tables 1, 2 와같으며, 노동부고시제 25-1-49( 작업환경측정및정도관리규정, 전문개정 25. 12. 3) 에제 26조측정방법에측정된작업장별작업기계의음압레벨은 Table 3 (3,4) 과같다. Tables 1, 2를보면대상작업장의경우 5 m 3 이하의협소한공간에서작업이이루어지고있으며, 주요구조부인바닥, 벽, 천장의 5 Hz 흡음률이 =.1.16인반사성이강한마감재료를사용한 Table 1 Dimension of the object loud-noisy Loud-noisy Indoor surface area(s) Indoor volume(v) 114.4 m 2 434.72 m 3 Model making 61.2 m 2 177.5 m 3 Loud-noisy Model making Table 2 Finishing material at before-improvement of the object loud-noisy Location Material 125 25 5 1k 2k 4k Floor Imitation stone finishing.2.2.2.3.4.4 Wall Water-based paint finish on the cement.1.1.2.2.2.3 Ceiling 9T sound-absorption tex.3.2.16.12.15.2 Door Common wooden door.14.1.6.5.1.1 Window Ordinary glass window.35.25.18.12.7.4 Floor Imitation stone finishing.2.2.2.3.4.4 Wall Water-based paint finish Ceiling on the cement.1.1.2.2.2.3 Door Common wooden door.14.1.6.5.1.1 Window Ordinary glass window.35.25.18.12.7.4 Partition Sandwich panel.1.1.1.2.2.2 Workplace Model making Table 3 Sound pressure level of working machine by each Working machine Electric db power 63 125 25 5 1k 2k 4k 8k (A) grinder.2 kw 58. 68.2 66.8 68. 7.9 69.3 6.9 59.6 74.3 Facet grinder.2 kw 67.9 68.1 65.3 63.8 66.5 69.5 66.7 61.9 74.4 Rock cutter.35 kw 86.6 92. 65.7 7. 67.8 71.5 71.3 59.5 79.2 Gloss grinder 84.4 77.1 86.6 8.9 8.5 8.9 81.4 77.1 88.2 8.9 Minute jewelry grinder.45 kw 61.4 62.4 68.2 67.9 73.5 77.2 71. 64.5 82.3 Small drill.8 kw 56.2 61. 5.1 62.4 63.3 56.9 54. 49.4 66. Disk sander.1 kw 63.4 67.1 61.2 62.7 56.8 62.3 58.6 59.8 67.5 Middle- typed table circular saw.4 kw 62.2 79.7 74.4 69.4 64.1 58.5 56.2 49.3 71.9 Middle- typed circular saw.2 kw 61.4 74.7 6.7 57.8 69.1 61.6 66.4 46.7 72.3 Table squash saw 1. kw 48.1 64.7 66.5 75.4 7.6 62.2 67.3 68.1 76.3 Table band saw machine.2 kw 5.5 51. 47.9 53.6 72.6 73.6 63.3 53.8 77.2 Small circular saw.8 kw 71.9 74.7 57.2 68.2 69.3 77. 89.8 91.3 94.4 Machine electric plane.5 kw 58.6 76.6 86.3 9.9 93.1 92.7 9.9 87.7 98.6 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년 /743
윤재현 김재수 Table 4 NR and decided frequency of working machine by each Loud-noisy Model making Working machine NR Decision frequency (Hz) grinder NR-71 2, Facet grinder NR-72 2, Rock cutter NR-81 125 Gloss grinder NR-85 4, Minute jewelry grinder NR-79 2, Small drill NR-63 1, Disk sander NR-66 8, Middle-typed table circular saw NR-66 125 Middle-typed circular saw NR-7 4, Table squash saw NR-74 8, Table band saw machine NR-75 2, Small circular saw NR-96 8, Machine electric plane NR-95 4, Table 5 Finishing material at after-improvement of the object loud-noisy Loud-noisy Location Finishing material 125 25 5 1k 2k 4k Floor Imitation stone.2.2.2.3.4.4 finishing Wall 12T rock wool sound-absorpt.2.2.4.6.7.75 Ceiling ion panel 1) Sound-absorp tion ceiling.55.55.58.63.68.59 panel Door Soundproof.6.13.1.1.1.1 door Double pane Window window + curtain 2).15.25.5.75.8.85 Floor Imitation stone.2.2.2.3.4.4 finishing Wall 12T rock wool sound-absorpt ion panel 1).2.2.4.6.7.75 Model Sound-absorp making Ceiling tion ceiling.55.55.58.63.68.59 panel Door Soundproof.6.13.1.1.1.1 door double pane Window window + curtain 2).15.25.5.75.8.85 Partition Sandwich panel.1.1.1.2.2.2 1) Space of the basement.7 m is existing same 2) Wrinkles curtain 5 % 것을알수있다. 또한 Table 3을보면각작업장에서사용하는작업기계의음압레벨은 66. 98.6 db(a) 로매우높게나타났다. 이러한결과로미루어볼때대상고소음작업장의경우반사성이강한마감재료로인하여높은음압레벨를갖는작업기계소음이내부공간에서더욱증폭되어작업자로하여금신체적 정신적악영향을미칠것으로사료된다. 2.2 NR곡선에의한평가이연구에서는대상고소음작업장의흡음대책을위해 ISO에서제안하는 NR평가방법을이용하였다. NR곡선 (noise rating curves) 은소음을청력장해, 회화방해, 시끄러움의 3가지관점에서평가하여 1961년 ISO가정한소음평가곡선으로 1, Hz의옥타브밴드레벨이평가곡선의 NRN(noise rating number) 과일치하고있다. 이를토대로하여각작업장별작업기계의주파수분석된결과를 1/1 옥타브밴드로하여 NR곡선으로평가해본결과는 Table 4와같다. Table 4를보면연구대상작업장에서사용하는작업기계의 NR등급결정주파수가대부분 1, 8, Hz의중 고음역대에서결정되므로이주파수대역에서흡음성능이높은마감재료를사용하여소음저감대책수립을하면효과적일것으로사료된다. 따라서이연구에서는위와같은사항을고려하여작업장의특성에알맞은 Table 5와같은마감재료의개선안을제안하였다. 2.3 작업장의잔향시간측정작업장잔향시간측정의경우 ISO 3382에준하여실시하였으며, 음원은 ISO에서제안하는무지향성스피커 (DO12 : omni-directional speaker) 를 1.5 m 높이에마이크로폰은높이는 1.2 m로하여각벽면과최소 1m이상이격시켜측벽반사에의한영향이미치지않도록하였다. 또한시뮬레이션의신뢰도를높이기위해작업기계가위치한곳에수음점을선정하여측정을실시하였다. 측정장비구성및측정장면과측정위치는 Figs. 1, 2와같다. 2.4 Computer Simulation 이연구에서사용된프로그램은 Odeon ver. 4.21 이며, 실측된잔향시간과의정확한비교를위해음원 744/ 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년
가청화를이용한고소음작업장의흡음대책평가 (a) Fig. 1 Scene from psycho-acoustic experiment (b) Model making Fig. 3 3-dimensional modelling of the object loudnoisy (a) 및수음점은동일하게설정하였다 (2). 또한작업장의크기가작기때문에 impulse response 길이를 2,5 으로하였으며, 온도및습도는잔향시간측정일과동일하게하였다. 위의내용을바탕으로한대상작업장의 3차원모델링된 (6) 모습은 Fig. 3과같다. 3. 분석및고찰 (b) Model making Fig. 2 One side and survey location of the object loud-noisy 3.1 음향시뮬레이션을통한개선전 후비교 (1) 실측된잔향시간과음향시뮬레이션과의비교작업장별로실측된잔향시간을동일하게모델링한음향시뮬레이션상의예측값과비교한것은 Table 6 과 Fig. 4와같다. Table 6과 Fig. 4를보면실측치와예측치의결과값이거의유사한패턴을보이고있음을알수있다. 또한보다더정확한비교를위해.9이상이면신뢰도를확보하는 cronbach's 계수를이용하여확인해본결과보석가공장은.95, 모형공작실은.972의높은신뢰도로나타났다. 따라서시뮬레이 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년 /745
윤재현 김재수 션예측치의신뢰성을확보하였다. (2) 음압레벨 (SPL) 비교 Table 5에서제시한마감재료로흡음대책을세운후실시하였으며, 이때작업기계별음향파워레벨 (PWL = SPL +2logr +8, 여기서 r = 이격거리 ) 은 Table 7 과같다. 소음에대한최대피해정도를알아보기위해모든작업기계가동시에작동한다는가정하에음향시뮬레이션을실시하였으며, 음향시뮬레이션을통하여나타난개선전 후의음압레벨결과는 Table 8과 Fig. 5와같다. Table 6 Comparison actual measured value with RT of predicted value(sec) Loudnoisy Comparison item Actual measured Reverb eration Model making time (RT) 125 25 5 1k 2k 4k 8k 1.55 1.67 1.64 1.67 1.67 1.52 1.23 value Predicted 1.41 1.69 1.66 1.71 1.76 1.42 1.15 value Actual measured.67.59.55.48.41.41.41 value Predicted value.73.66.59.58.54.51.46 RT (sec) RT (sec) 3 2.7 2.4 2.1 1.8 1.5 1.2.9.6.3 3 2.7 2.4 2.1 1.8 1.5 1.2.9.6.3 Actually Measured Value Before Improvement Predicted Value After Improvement 125 25 5 1 2 4 8 Average (a) Actually Measured Value Before Improvement Predicted Value After Improvement 125 25 5 1 2 4 8 Average (b) Model making Fig. 4 (By frequency) Comparison actual measured value with RT of predicted value Workplace Table 7 Working machine PWL by each (db) Working machine 63 125 25 5 1k 2k 4k 8k grinder 69.5 79.7 78.3 79.5 82.4 8.8 72.4 71.1 Facet grinder 79.4 79.6 76.8 75.3 78. 81. 78.2 73.4 Rock cutter 98.1 13.5 77.2 81.5 79.3 83. 82.8 71. Gloss grinder 88.6 98.1 92.4 92. 92.4 92.9 88.6 99.7 Minute jewelry grinder 72.9 73.9 79.7 79.4 85. 88.7 82.5 76. Small drill 67.7 72.5 61.6 73.9 74.8 68.4 65.5 6.9 Disk sander 74.9 78.6 72.7 74.2 68.3 73.8 7.1 71.3 Middle-typed table circular saw 73.7 91.2 85.9 8.9 75.6 7. 67.7 6.8 Model making Middle-typed circular saw 72.9 86.2 72.2 69.3 8.6 73.1 77.9 58.2 Table squash saw 59.6 76.2 78. 86.9 82.1 73.7 78.8 79.6 Table band saw mashine 62. 62.5 59.4 65.1 84.1 85.1 74.8 65.3 Small circular saw 83.4 86.2 68.7 79.7 8.8 88.5 11.3 12.8 Machine electric plane 7.1 88.1 97.8 12.4 14.6 14.2 12.4 99.2 746/ 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년
가청화를이용한고소음작업장의흡음대책평가 Table 8과 Fig. 5를보면개선전에비해개선후흡음력이높은마감재료의사용으로인해모든주파수의음압레벨이감소한것을알수있다. 또한음압레벨의경우흡음되는면적이개선전에비해 개선후많아진보석가공장은 9.1 db(a) 가감소한반면, 이보다흡음되는면적이보다적은모형공작실은 3.7 db(a) 가감소하였으나대상작업장모두소음이크게감소하여작업자로하여금개선전보다 11 3 SPL (db 15 1 95 9 85 8 75 Comparison Room (m 2 ) 25 2 15 1 7 5 65 6 125 25 5 1 2 4 8 db(a) (a) 125Hz 25Hz 5Hz 1Hz 2Hz 4Hz Frequency (Hz) (a) SPL (db 11 15 1 95 9 85 8 75 Comparison Room 2 (m ) 3 25 2 15 1 7 65 5 6 125 25 5 1 2 4 8 db(a) (b) Model making Fig. 5 Comparison SPL at before-improvement afterimprovement 125Hz 25Hz 5Hz 1Hz 2Hz 4Hz Frequency (Hz) (b) Model making Fig. 6 Comparison constant at before-improvement after-improvement Loud-noisy Model making Table 8 Comparison SPL at before-improvement after-improvement(db) Comparison item 125 25 5 1k 2k 4k 8k db(a) Sound pressure level (SPL) Before-improvement 91.8 81.4 81.4 82.6 84. 78.9 86.4 9.3 After- improvement 88.3 76.5 74.4 73.1 73.2 68.8 77.4 81.2 Before-improvement 82.6 86.2 9.9 93.1 92.5 92.6 91.9 99.3 After- improvement 8.7 84.2 87.9 89.4 88.6 89.1 88.8 95.6 Table 9 Comparison constant at before-improvement after-improvement(m 2 ) Loud- noisy Comparison item 125 25 5 1k 2k 4k Before-improvement 47.4 31.8 26.5 21.7 26.4 33.7 After-improvement 17.8 11.8 155.9 219.6 265.1 25.4 Room constant Model making Before-improvement 7.31 5.96 6.45 6.35 6.61 7.75 After- improvement 62.3 64.6 95.1 137.5 166.4 16.8 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년 /747
.15.1.5. -.5 -.1 -.15 윤재현 김재수 개선후소음으로인한피해가크게감소할것으로사료된다. (3) 실정수 ( constant) 고소음작업장의작업기계에서발생한소음은직접음과잔향음성분으로구분되어작업장내의음압레벨에영향을미친다. 이중직접음은기계자체의방음대책으로제어할수있지만잔향음은실의마감재료를변경해야만제어할수있다. 따라서작업장내에흡음되는면적이적을경우내부의울림이더욱더커지기때문에소음레벨을감소시키기위해서는실내의흡음에관한평가지표인실정수 ( constant) 를크게할수록좋다. 개선전 후연구대상작업장의마감재료별흡음률에따른실정수를비교분석한결과는 Table 9와 Fig. 6과같다. 실정수는실의체적과평균흡음률에따라그값을달리한다. Table 9와 Fig. 6을보면음향시뮬레이션을통해개선전에비해개선후흡음력이높은마감재료로흡음대책을세운결과실내체적이 434.72 m 3 인보석가공 5 Hz의실정수가 26.49 m 2 에서 155.92 m 2 로, 실내체적이 177.5 m 3 인모형공작실은 6.45 m 2 에서 95.9 m 2 로높아졌다. 이러한결과로미루어볼때실정수가높을수록잔향음이흡수되어음압레벨이감소하기때문에효율적인마감재료를선정하여소음을흡수하면고소음작업장의소음레벨을저감시킬수있을것으로사료된다. 3.2 가청화를이용한개선전 후의저감효과평가 (1) 가청화음향시뮬레이션이연구에서사용한가청화 ( 可聽化 ) 기법은음향시뮬레이션을통해흡음대책을한고소음작업장의수음점에서구한임펄스응답 (impulse response) 과직접작업장에서측정한작업기계의음원을합성연산 (convolution) 하여개선전과개선후의음향상태를직접들어볼수있는방법이며, 가청화의과정은 Fig. 7과같다. Envelop [ID=29] Ch. 1 Pa/s X1=. Y1= 1.25e-4X2= 1.229Y2= -1.651e-4 Acoustic property of the loud-noisy Listening in the anechoic Vocabulary : Loud Not at all Convolution Recording of working machine noise Listening with the headphone Fig. 7 Auralizational process Almost not Little A little bit Noisy Fairly noisy Very much noisy 1 2 3 4 5 6 7 8 9 1 11 12 13 Vocabulary : Noisy Not at all Almost not Little A little bit Noisy Fairly noisy Very much noisy 1 2 3 4 5 6 7 8 9 1 11 12 13 Vocabulary : Nervous Not at all Almost not Little A little bit Noisy Fairly noisy Very much noisy 1 2 3 4 5 6 7 8 9 1 11 12 13 Vocabulary : Unpleasant Not at Very much Almost not Little A little bit Noisy Fairly noisy all noisy 1 2 3 4 5 6 7 8 9 1 11 12 13 Vocabulary : Sharp (2) 청감평가를위한평가어휘조사이연구에서는작업기계소음에대해노출시피험자로하여금반응의정도를판단하기위해선행연구결과의어휘로구성된응답지 (sheet) 를사용하 Not at all Almost not Little A little bit Noisy Fairly noisy Very much noisy 1 2 3 4 5 6 7 8 9 1 11 12 13 Fig. 8 Psycho-acoustic sheet 748/ 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년
가청화를이용한고소음작업장의흡음대책평가 였으며, 어휘척도에따른반응의정도는 13단계 SD 척도를이용하였다. 또한현장성있는실험을위해설문전음원에해당하는작업기계를사진으로보여주며어휘에대한설명을충분히하였다. 이연구에서사용한응답지는 Fig. 8과같다. (a) (b) Model making Fig. 9 Comparison auralizational sound source from at before-improvement after-improvement (3) 청감평가를위한음원의구성청감실험시사용한개선전음원은현장에서녹음한각작업기계의음원을합성연산하여구성하였으며, 개선후음원은음향시뮬레이션상에서가청화기법을이용하여흡음처리에의한음원을사용하였다. 또한이연구에서사용된가청화음원은소음에대한최대피해정도를알아보기위해모든작업기계가동시에작동한다는가정하에음향시뮬레이션을실시하였다. 각작업기계별소음특성을 Cool Edit Pro 2.1을통해합성연산한개선전 후의음원형태는 Fig. 9와같다. (a) Psycho-acoustics laboratory (4) 청감평가방법및실험흡음대책후변화된음압레벨특성을정확하게파악하기위해피험자로선정한사람은모두정상적인청력을가진 2대의신체건강한대학생및대학원생 2명을대상으로하였다. 또한청감평가를실시하기전음향에대한이해를돕기위해평가시트를사전에나누어주고충분한설명과함께반복적으로음원을들려준뒤실험에참가하도록하였다. 실험장소는 Fig. 1과같이무향실과같은조건인원광대학교청감실험실 (psycho-acoustics chamber) 에서실시하였다. 음원의제시과정은 Fig. 11과같으며, 하나의음원을개선전과개선후로들려주는방식으로진행하였다. (b) Psycho-acoustics experiment Fig. 1 Floor plan and experiment scene of psychoacoustics laboratory Fig. 11 Presentation process of sound source (5) 각평가어휘에대한평균적반응항목대상고소음작업장의개선전 후의각항목별응답결과는 Fig. 12와같다. Fig. 12를보면개선전보석가공장의경우 9.3 db(a) 의높은음압레벨로인하여각항목의평균적반응치가 8.55~11.25의결과로높게나타났으며, 모형공작실은보다높은음압레벨인 99.3 db(a) 로인하여각항목의평균적반응치가 11.95~12.35의매우높은결과로나타났다. 또한모든항목에대한 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년 /749
윤재현 김재수 평균적반응치가 1이상을기록한데반해보석가공장에서의 날카롭다 항목은 8.55로나타났다. 이러한이유는인간의청각은고주파수에서민감하게반응하는데보석가공장에사용하는대부분의작업기계가모형공작실에서사용하는작업기계에비해 2~8 khz의고주파수대역에서음압레벨이낮기때문인것으로사료된다. Fig. 13을보면흡음대책을통한개선후음압레벨이 9.1 db(a) 가감소한보석가공장의경우각항목의 13 12 11 1 9 8 7 6 5 4 3 2 1 13 12 11 Loud Noisy Nervous Unpleasant Sharp (a) 평균적반응치에따른개선량은 크다 2.5, 시끄럽다 2.5, 신경쓰인다 2.95, 불쾌하다 2.45, 날카롭다 1.5로나타났으며, 3.7 db(a) 가감소한모형공작실은 크다 2., 시끄럽다 1.7, 신경쓰인다 1.7, 불쾌하다 1.55, 날카롭다 1.75 정도개선되었다. 이러한결과로미루어볼때고소음작업장을흡음재로마감하여고소음을저감할수있는방법이매우실효성있을것으로사료된다. (6) 대상고소음작업장의개선정도비교분석가청화를실시한대상고소음작업장의전체적인주관적인인상을알아보기위해평가어휘별로대상고소음작업장의대한개선전 후의빈도분석결과를정규분포곡선으로나타낸것은 Fig. 14와같다. Fig. 14를보면대상고소음작업장에서사용하는작업기계가매우높은음압레벨을발생시켜모든항목들이높게평가되었으나잔향음을제어하는흡음대책을통해고소음작업장의소음대책을강구한개선후의경우실험에참가한피험자들로하여금작업장소음환경개선에대해매우긍정적인반응을 1 9 8 7 6 5 4 3 Before-improvement After-improvement 2 1 Loud Noisy Nervous Unpleasant Sharp (b) Model making Fig. 12 Average reaction about each items through sound-absorption measure at beforeimprovement after-improvement 5 4.5 4 jewelry model making 3.5 Improvemen 3 2.5 2 1.5 1.5 Loud Noisy Nervous Unpleasant Sharp <Vocabulary> Fig. 13 Improved quantity about each items through sound-absorption measure at before-improvement after-improvement 75/ 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년
가청화를이용한고소음작업장의흡음대책평가 (b) model making Fig. 14 Frequency analysis, after-improvement(normal distribution curve) (a) Before-improvement After-improvement 보이는것으로나타났다. 만약이와같은흡음대책과함께직접음에해당하는작업기계자체의방음대책을강구한다면소음에대해보다더긍정적인반응을보일것으로사료된다. 4. 결론 이연구는고소음작업장소음대책의방안으로음향시뮬레이션기법을이용하여실측치와예측치의신뢰성을검토한후흡음대책을통해작업장소음의개선정도를예측해보았으며, 가청화청감실험을실시한결과는다음과같다. (1) 고소음작업장별로실측된잔향시간을동일하게모델링한음향시뮬레이션상의예측값과비교한결과주파수별로거의유사한패턴을보였다. 또한 cronbach's 계수가보석가공장은.95, 모형공작실은.972의높은신뢰도로나타나시뮬레이션을이용한예측치의신뢰성을확보할수있었다. (2) 음향시뮬레이션을기법을이용하여흡음대책을통한음압레벨의개선전 후결과전주파수에걸쳐음압레벨이감소하였으며, 음압레벨의경우도보석가공장은 9.1 db(a), 모형공작실은 3.7 db(a) 가감소하여고소음작업장의소음이크게개선된것을알수있었다. 또한 5 Hz 실정수의개선전 후결과보석가공장은 26.49 m 2 에서 155.92 m 2 로, 모형공작실은 6.45 m 2 에서 95.9 m 2 로실정수가높아졌다. 따라서실정수가높을수록발생하는내부소음이흡수되어음압레벨이감소하기때문에효율적인흡음대책을통한고소음작업장의소음대책 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년 /751
윤재현 김재수 이앞으로는매우중요할것으로사료된다. (3) 가청화청감평가결과개선전에는작업기계의높은음압레벨로인하여보석가공장은각항목의평균치가 8.55~11.25, 모형공작실은 11.95~ 12.35의매우높은결과로나타났다. 그러나흡음대책을통한개선후보석가공장은각항목의평균치에따른개선량이 1.5~2.95, 모형공작실은 1.55~2가감소하게나타났다. 따라서이러한결과로미루어볼때고소음작업장을흡음재로마감하여고소음을저감할수있는방법이매우실효성있을것으로사료된다. 또한이와같은흡음대책과함께직접음에해당하는작업기계자체의방음대책을강구한다면소음에대해작업자로하여금보다더쾌적한업무환경수립이가능할것으로사료된다. 이연구결과에서제시한흡음대책을통하여대상고소음작업장의작업환경을개선한다면작업자로하여금보다더쾌적한작업장환경수립이가능할것으로사료된다. 또한이연구와유사한다른연구들이지속된다면고소음작업장의소음저감대책시유용한자료로활용될수있을것으로사료된다. 참고문헌 (1) Kook, J. H., Jung, C. W., Jung, E. J. and Kim, J. S., 26, A Study on the Evaluation and Characteristics of Plumbing Noise in Building, Proceedings of The AIK '6 Autumn Annual Conference pp. 673~676. (2) Kim, J. S., 27, Architectural Acoustic Design (3rd edition), Sejin Co. (3) Evaluation Technique on Architectural Acousic Performance Using Auralization, Acoustical Materials Association of Korea, Vol. 3, Acoustic Material Technology, 27.8 (4) Yoon, J. H., Choi, D., Kim, J. S., 28, A Study on Characteristics of Noise generates when -Processing, Proceedings of the KSNVE Annual Autumn Conference, pp. 417~418. (5) Yoon, J. H., Kim, D. G., Kim, J. S., 28, A Study on Property of Machinery Noise Generates at Model Workshop, Proceedings of the Korean Society of Environmental Engineers, p.171. (6) Joo, D. H., Kook, J. H., Kim, J. S., 27, Typical of Vocabulary for Evaluation on Instrument- Noise Generates at Loud Noisy Workplace, Proceedings of the KSNVE Annual Autumn Conference, KSNVE7A-1-16. (7) Yoon, J. H., Choi, D., Kim, J. S., 28, A Study on Sound-absorption Measure Using Acoustic Simulation for Loud-noisy Workplace, Proceedings of the KSNVE Annual Autumn Conference, pp. 619~62. 752/ 한국소음진동공학회논문집 / 제 2 권제 8 호, 21 년