The NoiseGuide indicates the noise levels using red, yellow and green lights, like a traffic light. The "ear" part indicates the current levels, the bottom bar indicates the longer term background noise levels.
While the ear symbol shows the current noise levels, responding instantly to loud voices or other noise, the bar at the bottom shows whether the overall background noise is getting too high. This uses the average sound over last 15, 30 or 60 minutes.
NoiseGuide Kits with Power Supply, Data Logging USB Stick and Software.