{"data":{"id":"us/49-cfr-appendix-a-to-part-227","jurisdiction":"us","citation":"49 CFR Appendix A to Part 227","heading":"Appendix A to Part 227—Noise Exposure Computation","body":"This appendix is mandatory.\nI. Computation of Employee Noise Exposure\nA. Noise dose is computed using Table A-1 as follows:\n1. When the sound level, L, is constant over the entire work day, the noise dose, D, in percent, is given by: D = 100 C/T, where C is the total length of the work day, in hours, and T is the duration permitted corresponding to the measured sound level, L, as given in Table A-1.\n2. When the work day noise exposure is composed of two or more periods of noise at different levels, the total noise dose over the work day is given by:\nD = 100 (C1/T1 + C2/T2 + . . . + Cn/Tn), where Cn indicates the total time of exposure at a specific noise level, and Tn indicates the duration permitted for that level as given by Table A-1.\nB. The eight-hour TWA in dB may be computed from the dose, in percent, by means of the formula: TWA = 16.61 log10 (D/100) + 90. For an eight-hour work day with the noise level constant over the entire day, the TWA is equal to the measured sound level.\nC. Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level.\nD. Any time that an employee spends deadheading shall be included in the calculation of the noise dose.\nE. A table relating dose and TWA is given in Section II of this Appendix.\nTable A-1 1\nA-weighted sound level, L (decibel) Duration permitted T (hour)\n80 32\n81 27.9\n82 24.3\n83 21.1\n84 18.4\n85 16\n86 13.9\n87 12.1\n88 10.6\n89 9.2\n90 8\n91 7.0\n92 6.1\n93 5.3\n94 4.6\n95 4\n96 3.5\n97 3.0\n98 2.6\n99 2.3\n100 2\n101 1.7\n102 1.5\n103 1.3\n104 1.1\n105 1\n106 0.87\n107 0.76\n108 0.66\n109 0.57\n110 0.5\n111 0.44\n112 0.38\n113 0.33\n114 0.29\n115 0.25\n116 0.22\n117 0.19\n118 0.16\n119 0.14\n120 0.125\n121 0.11\n122 0.095\n123 0.082\n124 0.072\n125 0.063\n126 0.054\n127 0.047\n128 0.041\n129 0.036\n130 0.031\n140 0.078\n1 Numbers above 115 dB(A) are italicized to indicate that they are noise levels that are not permitted. The italicized numbers are included only because they are sometimes necessary for the computation of noise dose.\nIn the above table the duration permitted, T, is computed by\nwhere L is the measured A-weighted sound level.\nII. Conversion Between “Dose” and “8-Hour Time-Weighted Average” Sound Level\nA. Compliance with subpart B of part 227 is determined by the amount of exposure to noise in the workplace. The amount of such exposure is usually measured with a dosimeter which gives a readout in terms of “dose.” In order to better understand the requirements of the regulation, dosimeter readings can be converted to an “8-hour TWA.”\nB. In order to convert the reading of a dosimeter into TWA, see Table A-2, below. This table applies to dosimeters that are set by the manufacturer to calculate dose or percent exposure according to the relationships in Table A-1. So, for example, a dose of 91 percent over an eight-hour day results in a TWA of 89.3 dB, and a dose of 50 percent corresponds to a TWA of 85 dB.\nC. If the dose as read on the dosimeter is less than or greater than the values found in Table A-2, the TWA may be calculated by using the formula: TWA = 16.61 log10 (D/100) + 90 where TWA = 8-hour time-weighted average sound level and D = accumulated dose in percent exposure.\nTable A-2—Conversion From “Percent Noise Exposure” or “Dose” to “8-Hour Time-Weighted Average Sound Level” (TWA)\nDose or percent noise exposure TWA\n10 73.4\n15 76.3\n20 78.4\n25 80.0\n30 81.3\n35 82.4\n40 83.4\n45 84.2\n50 85.0\n55 85.7\n60 86.3\n65 86.9\n70 87.4\n75 87.9\n80 88.4\n81 88.5\n82 88.6\n83 88.7\n84 88.7\n85 88.8\n86 88.9\n87 89.0\n88 89.1\n89 89.2\n90 89.2\n91 89.3\n92 89.4\n93 89.5\n94 89.6\n95 89.6\n96 89.7\n97 89.8\n98 89.9\n99 89.9\n100 90.0\n101 90.1\n102 90.1\n103 90.2\n104 90.3\n105 90.4\n106 90.4\n107 90.5\n108 90.6\n109 90.6\n110 90.7\n111 90.8\n112 90.8\n113 90.9\n114 90.9\n115 91.1\n116 91.1\n117 91.1\n118 91.2\n119 91.3\n120 91.3\n125 91.6\n130 91.9\n135 92.2\n140 92.4\n145 92.7\n150 92.9\n155 93.2\n160 93.4\n165 93.6\n170 93.8\n175 94.0\n180 94.2\n185 94.4\n190 94.6\n195 94.8\n200 95.0\n210 95.4\n220 95.7\n230 96.0\n240 96.3\n250 96.6\n260 96.9\n270 97.2\n280 97.4\n290 97.7\n300 97.9\n310 98.2\n320 98.4\n330 98.6\n340 98.8\n350 99.0\n360 99.2\n370 99.4\n380 99.6\n390 99.8\n400 100.0\n410 100.2\n420 100.4\n430 100.5\n440 100.7\n450 100.8\n460 101.0\n470 101.2\n480 101.3\n490 101.5\n500 101.6\n510 101.8\n520 101.9\n530 102.0\n540 102.2\n550 102.3\n560 102.4\n570 102.6\n580 102.7\n590 102.8\n600 102.9\n610 103.0\n620 103.2\n630 103.3\n640 103.4\n650 103.5\n660 103.6\n670 103.7\n680 103.8\n690 103.9\n700 104.0\n710 104.1\n720 104.2\n730 104.3\n740 104.4\n750 104.5\n760 104.6\n770 104.7\n780 104.8\n790 104.9\n800 105.0\n810 105.1\n820 105.2\n830 105.3\n840 105.4\n850 105.4\n860 105.5\n870 105.6\n880 105.7\n890 105.8\n900 105.8\n910 105.9\n920 106.0\n930 106.1\n940 106.2\n950 106.2\n960 106.3\n970 106.4\n980 106.5\n990 106.5\n999 106.6","path":["Title 49—Transportation","Subtitle B—Other Regulations Relating to Transportation","CHAPTER II—FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION","PART 227—OCCUPATIONAL SAFETY AND HEALTH IN THE LOCOMOTIVE CAB"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-49.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:34Z","sha256":"c6d199a1331bc08b99f2bbba74c70ff1e1be91702780af53af51c1ab4cf64e67","source_id":"us-cfr","stale":true,"prev":"us/49-cfr-227.219","next":"us/49-cfr-appendix-b-to-part-227"},"notice":"GroundRules: Original legal text. Not legal advice."}