Appendix B
141
Models SE and DL
LDN
Representing the Day/Night sound level, this m easurement is a 24-hour average sound level
where 10 dB is added to all of the readings that occur between 10pm and 7am. This is
primarily used in community noise regulations where t here is a 10 dB “penalty” for night time
noise. Typically LDN’s are measured using A weig hting, a 3 dB Exchange Rate, and no
Threshold.
L_Mn
Minimum SPL. Lowest SPL measured over a time int erval.
L_Mx
Maximum SPL. Highest SPL measured over a tim e interval.
Logging
In sound studies, the saving of measurements at f ixed intervals during a study, where each
measurement is determined from data processed in the previous logging interval.
L_Pk
Peak SPL. This is the highest SPL value obtained duri ng a study or a session. A peak SPL
measurement is affected by the frequency response s etting but not by the time response
setting of the meter.
Octave band
An Octave band is defined as a frequency band whose upper band-edge frequency is twice
the lower band frequency.
Noise
Unwanted sound.