How do I input Ldn and Lden data in TNM Version 2.1 and above?
(Applies to TNM version 2.1 and 2.5) Calculations for Ldn and Lden have been modified in TNM Version 2.1 and above to incorporate accurate numbers of hours (Ldn: 15 hours day and 9 hours night; Lden: 12 hours day, 3 hours evening and 9 hours night). The calculations for Ldn and Lden in TNM Version 2.0 and all previous versions assumed the entered ADT value was split evenly between day and night for Ldn and day, evening, and night for Lden. For example, for Ldn the previous versions assumed the same total traffic passed by during the 15-hour day as passed by during the 9-hour night. This resulted in higher hourly volumes during the night than during the day, because the same 15 hours of daytime traffic was compressed into only 9 nighttime hours. Because the calculations were not accounting for the different number of hours included in day, evening, and night, erroneously high sound levels were being calculated for Ldn and Lden. TNM Version 2.1 and above accounts for actual numbers of ho
