Mean of N Previous Pings
This operator creates an echogram in which each sample in each ping is the mean value of the same sample in the previous n pings.
Enter n (the number of previous pings over which the mean value of each sample is calculated) on the Mean of n previous pings page on the Variable Properties dialog box. The mean is taken in linear space (i.e. not dB), and includes the n pings previous to the ping prior to the current ping, but does not include the current ping to calculate the mean. That is, if the window size is 2, and you are looking at ping 3, it is the mean of pings 1 and 2 that is taken, not the mean of pings 1, 2 and 3 or the mean of pings 2 and 3.
Where the number of available previous pings is less than the specified n value (e.g. ping 2 where n = 5), Echoview will use all available previous pings.
Echoview accepts a single operand of the following data types as input:

multibeam magnitude

multibeam SV

multibeam TS

multibeam unspecified dB
Hint: This operator was introduced primarily to support multibeam target detection. In this application it is used to identify background objects (objects that appear in the same place in n beams) so they can be removed prior to detecting targets. See the Multibeam target detection operator for more information.
Settings
The Mean of N Previous Pings Variable Properties dialog box pages include (common) Variable Properties pages and these operator pages:
Operands page
Mean of N Previous Pings page
Setting 
Description 
Window size 
The Window size setting determines the number (n) of previous pings over which the mean value of samples is calculated. For example if you select 10, then the data on ping i will be the mean of pings i10 to ping i1 in the operand. 