Larson Davis System 824, Training Manual

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3/22/01 Environmental Measurements 2-7
For each Interval period the following are recorded automat-
ically:
For each Interval period the following can be optionally
selected:
***Special advanced feature
Since Ln’s cannot be combined over time, the 824 and DNA
software (also 824 Utility software) store and process the
binary Ln table for every interval in a way that records can
be combined and any percentiles may be calculated (post
processed) at any time.
Time synchronization
One feature of the Interval History is its ability to be syn-
chronized with the time of day clock. This allows each inter-
val record, for example, to begin at the start of each new
hour of the day. Syncing can be done to the following incre-
ments of time:
• 1 minute
• 5 minutes
• 10 minutes
• 15 minutes
• 20 minutes
• 30 minutes
• 60 minutes
Metric Explanation of Metric
Leq (dB) w/selected weighting Short Leq average of all energy during interval
SEL (dB) w/selected weighting SEL of all energy during interval
Lmin (dB) w/selected weighting Minimum instantaneous SPL during the interval
Lmax (dB) w/selected weighting Maximum instantaneous SPL during the interval
Lpeak-I (dBF) Greatest peak level during the interval
Lpeak-II (dB) w/selected weighting Greatest peak level during the interval
Metric Explanation of Metric
Six Ln values (broadband)
***
The level that the instantaneous SPL was over for n% of the time