Soft dB Opus Suite SLM 4-Ch Module - Manual (Page 23)

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6.5 Reference Value
The reference value is the unit reference from which the decibel (dB) is calculated.
6.6 FFT High Pass Filter
The FFT spectrum frequency bandwidth can be adjusted from a variety of choices:
Bandwidth FFT Lines Frequency Resolution
20 kHz 854 23.4 Hz
10 kHz 854 11.7 Hz
5 kHz 854 5.85 Hz
3.33 kHz 854 3.90 Hz
2 kHz 854 2.34 Hz
1 kHz 854 1.17 Hz
An electronic high-pass filter set at 0.9 Hz is applied on the input to block any DC. However, another
filter can be applied to the FFT Spectrum to match the 1/3 octave spectrum frequency span, which is
6.3 Hz to 20 kHz if 1 or 2 inputs are enabled an 20 Hz to 20 kHz if 3 or 4 inputs are enabled.
The high pass filter cut-off frequency can be lowered but the global level resulting from the sum of
the FFT lines may be different than the SLM global levels (LS, LF, LI, Leq and SEL) and their associated
1/3 Octave Spectrum.