Larson Davis 824 Technical Reference Manual

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Larson Davis 824 Technical Reference Manual Manual pdf 566 page image

C-20 824 Reference Manual 9/29/091/1 and 1/3 Octave FiltersThe 1/1 and 1/3 octave filters (SSA and RTA Options)comply with all requirements of IEC 61260:1995 includingamendment 1 (2001) for Class 1. These digital filters aresampled at a rate of 51,200 samples per second, with base 2center frequencies and having real-time performance for allfilters. The 0 dB gain setting is the reference range and thereference input signal is 1 Volt rms at 1 kHz.Frequency Range 1/1 Octave Filters: 16 Hz to 16 kHz1/3 Octave Filters: 12.5 Hz to 20 kHzFilter Shapes: Filters are characterized by the shape of their filter skirts andthe shape of the passbands, which must fit within thosespecified by the standards. The following figures presentthese for the 1/3 octave band centered at 1 kHz. Overlaidwith these curves are the limit curves associated with IEC61260:1995 Class 1.Figure 13-2 Passband of 1kHz 1/3 Octave Filter115.00120.00125.000.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2Relative Frequencyamplitude (dB)1000 Hz PassbandIEC Class 1 Limits