Rationale

This ballot is part of the harmonization effort between E1007 and E336. In 2019, a revision was made to standard E336 (field sound transmission measurement) to change the way that the background sound level correction was calculated. This was approved and implemented in E336-19a. Previously, the background correction had stated: OLD: For (L_sb-L_b)<5,L_s=L_sb-2 For 5=(L_sb-L_b )=10,L_s=10log(10^(L_sb/10)-10^(L_b/10) ) For (L_sb-L_b )>10,L_s=L_sb This was changed to a new background correction that is more precise and consistent with other methodologies: NEW: For (L_sb-L_b )<6,L_2=L_sb-1.26 For (L_sb-L_b )=6,L_2=10log(10^(L_sb/10)-10^(L_b/10) ) The rationale for ballot E33 (19-03) Item 6 for E336 (which passed) stated: This is the first of a series of ballots on E33.03 standards to update the background adjustment method in them. Please do not ignore this ballot and then cast a negative on a future ballot making the same change on another standard. Previous versions of this ballot have drawn negatives. The major change in this version is the expansion of the proposed section 13.5.4. Wording has been changed in several places as a result of comments received. The standard in section 11.4.2.1 currently clearly directs the user to compute the average levels in the room when using fixed microphones before providing direction on background adjustment. This provides a consistent method for both fixed and scanned microphones. However, earlier versions of the standard directed the user to background adjust each microphone position before averaging when using fixed microphones. Some users are still adjusting individual microphone positions. This change clarifies that levels are averaged and adds bars over the terms of equation 7. Current practice of not adjusting results where the difference between combined level and background is greater than 10 dB results in an arbitrarily introduced potentially significant error especially when the difference is just above 10 dB. The adjustment of 2 dB currently required when the combined level is within 5 dB of the background introduces an undesirable adjusted level that is lower than the actual signal level when the difference is between 4 and 5 dB. This proposal first requires background adjustment of all data using Equation 7 for cases where the difference between total level and background level is 6 dB or greater. It is clarified that no rounding is to be done in the calculation. When the difference is less than 6 dB, the adjustment is set at 1.26 dB consistent with ISO methodologies. The word “corrected” is changed to “adjusted.” The point at which results are identified as providing only an estimate of a lower limit is also set at a difference of less than 6 dB. A requirement is added to the report section to mark frequencies where the difference is less than 6 dB and to include an explanatory note. Since that time, the same change has been implemented in E90 and E2964. This ballot applies the revised correction calculation to E1007. It also implements the same wording used in E336 for the report. The reporting for ISPL/RTNISPL/ANISPL values is updated to match what is currently in E336.