Highpass filter
The analog inputs S1 and S2 are equipped with analog highpass filters to reduce noise from wind or other sources with
frequencies below the frequency range for ordinarry sound measurements. The filter is switched on if the limited frequency
range is selected (+>6,3Hz). When this filter is “Off” the lower frequency is 0.4 Hz. This setting is in use when the
optional octave or third octave filter is set to “W” (for wide), or when the second weighting network “Z-wide” is selected
Filter type: 3rd order HP filter (-3 dB at 3,4 Hz, Butterworth response)