Larson Davis System 824, Technical Reference Manual

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C-20 824 Reference Manual 9/29/09
1/1 and 1/3 Octave Filters
The 1/1 and 1/3 octave filters (SSA and RTA Options)
comply with all requirements of IEC 61260:1995 including
amendment 1 (2001) for Class 1. These digital filters are
sampled at a rate of 51,200 samples per second, with base 2
center frequencies and having real-time performance for all
filters. The 0 dB gain setting is the reference range and the
reference input signal is 1 Volt rms at 1 kHz.
Frequency Range
1/1 Octave Filters: 16 Hz to 16 kHz
1/3 Octave Filters: 12.5 Hz to 20 kHz
Filter Shapes: Filters are characterized by the shape of their filter skirts and
the shape of the passbands, which must fit within those
specified by the standards. The following figures present
these for the 1/3 octave band centered at 1 kHz. Overlaid
with these curves are the limit curves associated with IEC
61260:1995 Class 1.
Figure 13-2 Passband of 1kHz 1/3 Octave Filter
115.00
120.00
125.00
0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2
Relative Frequency
a
m
plitude
(dB)
1000 Hz Passband
IEC Class 1 Limits