Larson Davis 831C-FFT, Reference Manual

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SoundAdvisor Model 831C Understanding Level and Dynamic Triggering 136
FIGURE 17-11
Event History with Dynamic Triggering and Events
1.
With dynamic triggering, events only occur if the level exceeds the background level
plus the offset. Here the offset is 20 dB.
2.
The bars represent events logged during the measurement. There are about 11 with a
Minimum Duration of 3 seconds.
About the Background Level
The background sound level used with dynamic triggering is the user-indicated
Ln
level
( Setup Manager

Ln Tab ). It’s calculated using an algorithm that includes the rise rate in
dB per minute. There are 5 Dynamic Trigger Parameters options available:
When the measurement first begins, the background tracking level is set to the following:
Trigger Level SPL 1 – Offset = Initial Background Level
As the sound level increases above the background tracking level, the tracking level
increases at the rise rate. As the sound decreases below the tracking level, the tracking
level decreases at the rate determined by the dynamic response (Ln Percentile and its
rate). Thus, the dynamic trigger level is set to the following:
Background level + Offset = Trigger Level
0
10
20
30
40
50
60
70
80
90
100
0:00:00 1:56:39 3:53:19 5:49:59 7:46:39 9:48:18 11:44:58 13:41:38 15:38:18 17:34:58 19:31:38 21:28:18 23:24:58
Leq Background tracking level Dynamic Event Dynamic Trigger Level
2.
1.
Table 17.2 Dynamic Response
Setting Number
Tracking Ln
Percentile
Rise Rate, dB/
minute
Description
1 95% 1/2 Lower tracking level
2 90% 1/3 Slow
3 90% 1/2 Default, normal operation
4 90% 1 Fast
5 80% 1 Fast and higher tracking level