Frequently Asked Questions

When setting up the 831 to log exceedances, you need to specify a trigger method:

 - LEVEL – this is straightforward, simply the level at which an event is triggered.

The trigger is defined at the first level reached of RMS (SPL 1) and peak (Peak 1) value.

- DYNAMIC – unique feature of Model 831.

Why choose Dynamic?

Imagine the neighbor’s dog barking during the day.  Because of the amount of background noise (cars driving by, people mowing their lawn, kids playing in the yard) this would not be considered a significant

noise event. However, if that same dog were barking

at midnight, it would be annoyance.

Since the dog hasn’t gotten any louder, applying the same level trigger for the entire 24-hour measurement would not yield useful data. The plot above right shows a standard trigger situation. As you can see, some events were missed due to being below the trigger level.

This is where the dynamic trigger comes in handy. By tracking the background noise level or L90 (level exceeded 90% of the time, shown in red) and adding an offset to it (15 dB offset shown in blue) we can determine better when an event occurs.  A very useful feature for unattended monitoring applications.

Dynamic Trigger Setup

Dynamic Response Setting Number

To select the setting number, start by using the default setting (3). If you find that you’re missing events because the trigger level went up too much during an event, then make it slower and see if triggering is improved.  If you find that you’re getting false events because the background levels are changing too fast, then make it faster so that the 831 is more responsive to changes in background level.