14 CFR Ch. I (1-1-19 Edition) SPL-(i,k), may be determined from the narrow band analysis and used to compute a revised tone correction factor for that particular one-third octave band. Other methods of rejecting spurious tone corrections may be approved. A36.4.3.2 The tone correction procedure will underestimate EPNL if an important tone is of a frequency such that it is recorded in two adjacent one-third octave bands. An applicant must demonstrate that either: (a) No important tones are recorded in two adjacent one-third octave bands; or (b) That if an important tone has occurred, the tone correction has been adjusted to the value it would have had if the tone had been recorded fully in a single one-third octave band. A36.4.4 Maximum tone-corrected perceived noise level A36.4.4.1 The maximum tone-corrected perceived noise level, PNLTM, must be the maximum calculated value of the tone-corrected perceived noise level PNLT(k). It must be calculated using the procedure of section A36.4.3. To obtain a satisfactory noise time history, measurements must be made at 0.5 second time intervals. NOTE 1: Figure A36-2 is an example of a flyover noise time history where the maximum value is clearly indicated. NOTE 2: In the absence of a tone correction factor, PNLTM would equal PNLM. A36.4.4.2 After the value of PNLTM is obtained, the frequency band for the largest tone correction factor is identified for the two preceding and two succeeding 500 ms data samples. This is performed in order to identity the possibility of tone suppression at PNLTM by one-third octave band sharing of that tone. If the value of the tone correction factor C(k) for PNLTM is less than the average value of C(k) for the five consecutive time intervals, the average value of C(k) must be used to compute a new value for PNLTM. A36.4.5 Duration correction. A36.4.5.1 The duration correction factor D determined by the integration technique is defined by the expression: 788 VerDate Sep<11>2014 12:50 Apr 30, 2019 Jkt 247046 PO 00000 Frm 00798 Fmt 8010 Sfmt 8002 Y:\SGML\247046.XXX 247046 ER08JY02.004 spaschal on DSK3GDR082PROD with CFR Pt. 36, App. A