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5 slm dynamic range, 6 slm fft high pass filter, Slm dynamic range – Soft dB Opus Suite SLM & 3Vib Module User Manual

Page 24: Slm fft high pass filter

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6.1.5

SLM Dynamic Range

The dynamic range of the SLM input is around 94 dB. Two ranges are available (Low or High)

2

. The

table below provides examples of the dynamic ranges for given sensitivities of 40 and 50 mV/Pa.

Microphone Sensitivity

40 mV/Pa

50 mV/Pa

Low Range

27 to 121 dB(A)

25 to 119 dB(A)

High Range

39 to 132 dB(A)

37 to 130 dB(A)

6.1.6

SLM FFT High Pass Filter

Several frequency bandwidths are available with the FFT spectrum:

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.

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.

2

Both low and high range should be available on the SLM input of a Concerto unit. Other hardware (such as

Alto-6ch and Itrack) may only have the low range available.