This Virtual Instrument analyzes data from environmental sound surveys. The upper window shows all the data from a one-hour survey session; the lower window shows a selected data segment that is time averaged to simulate sound level meter response. A histogram of the selected data is used to find noise descriptors such as Ln averages.
Data from a preschool playground survey was used to find the effect of group size on sound levels. The overall average sound level for the selected 45-minute survey segment was 53 dB The average L50 allowed by the local noise ordinance is 55 dB.
The selected record segment histogram has three distinct regions corresponding to different levels of playground activity. For the first 17 minutes, there were 12 children present and the average sound level was 49 dB. For the next 20 minutes, there were 25 children and the average sound level was 59 dB. For the last 6 minutes everyone was inside and the ambient sound level was 41 dB.