Pt. 150, App. B 14 CFR Ch. I (1-1-19 Edition) Symbols. NOTE: When a noise environment is caused by a number of identifiable noise events, such as aircraft flyovers, average sound level may be conveniently calculated from the sound exposure levels of the individual events occurring within a time period T: 1 Sec. A150.205 LT Ldni Ldn LAE Mathematical computations. (a) Average sound level must be computed in accordance with the following formula: L dn n - 10 T L AEi /10 i=1 L dn = 10 log10 365 1 - 365 10 L dni /10 (4) i=1 where Ldni is the day-night average sound level for the i-th day out of one year. (d) Sound exposure level must be computed in accordance with the following formula: 1 = 10 log10 to t2 - t1 NOTE: When T is one hour, LT is referred to as one-hour average sound level. (b) Day-night average sound level (individual day) must be computed in accordance with the following formula: 08:20 May 17, 2019 Jkt 247048 [Doc. No. 18691, 49 FR 49269, Dec. 18, 1984; 50 FR 5064, Feb. 6, 1985, as amended by Amdt. 150-1, 53 FR 8724, Mar. 16, 1988; Amdt. 150-4, 69 FR 57626, Sept. 24, 2004] APPENDIX B TO PART 150 - NOISE COMPATIBILITY PROGRAMS L ( t ) /10 10 A dt (5) PO 00000 Frm 00682 (3) where to is one second and LA(t) is the timevarying A-weighted sound level in the time interval t1 to t2. The time interval should be sufficiently large that it encompasses all the significant sound of a designated event. The requisite integral may be approximated with sufficient accuracy by integrating LA(t) over the time interval during which LA(t) lies within 10 decibels of its maximum value, before and after the maximum occurs. Sec. B150.1 Sec. B150.3 Sec. B150.5 Scope and purpose. Requirement for noise map. Program standards. 672 VerDate Sep<11>2014 (2) where LAEi is the sound exposure level of the i-th event, in a series of n events in time period T, in seconds. 0700 [ L A ( t ) +10 ] / 10 dt 1 - 0000 10 = 10 log10 2400 2200 L A (t) / 10 L A ( t ) +10 ] / 10 86400 [ + 10 dt + 10 dt - - 0700 2200 Time is in seconds, so the limits shown in hours and minutes are actually interpreted in seconds. It is often convenient to compute day-night average sound level from the onehour average sound levels obtained during successive hours. (c) Yearly day-night average sound level must be computed in accordance with the following formula: L AE L T = 10 log10 Symbol Average Sound Level, During Time T ..................... Day-Night Average Sound Level (individual day) ... Yearly Day-Night Average Sound Level ................. Sound Exposure Level ............................................ (1) where T is the length of the time period, in seconds, during which the average is taken; LA(t) is the instantaneous time varying Aweighted sound level during the time period T. The following symbols are used in the computation of Ldn; Measure (in dB) T O Fmt 8010 Sfmt 8002 Y:\SGML\247048.XXX 247048 EC15SE91.004 Sec. A150.203 dt EC15SE91.003 General. - 10 ER10FE03.003 Sec. A150.201 The following mathematical descriptions provide the most precise definition of the yearly day-night average sound level (Ldn), the data necessary for its calculation, and the methods for computing it. L A ( t)/10 T EC15SE91.001 PART C - MATHEMATICAL DESCRIPTIONS 1 L T = 10 log10 EC15SE91.000 wholly or partially within the Ldn 65 dB boundary. (b) For those agencies identified in (a) that have land use planning and control authority, the supporting documentation shall identify their geographic areas of jurisdiction.