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6-4
Technical Data
Left/right Output Level
Left and right output level is shown on a VU-type scale. The metering indicates absolute instantaneous peak (much
faster than a standard PPM or VU meter). The meter is scaled so that 0 dB is calibrated to the highest left and right
peak modulation level, before de-emphasis, that the processing will produce, under any program, processing, or
setup condition (except when the processing is switched to BYPASS). The meter indication is not affected by the
setting of the output level control.
Composite Output Level
The Orban 5750 Audio Processor controls instantaneous, absolute peak levels to a tolerance of approximately 0.1
dB. Composite modulation is indicated in percentage modulation, absolute instantaneous peak indicating. 100% is
calibrated to the highest composite peak modulation level that the processing will produce, including the pilot tone,
under any program, processing, or setup condition (except when the processing is switched to BYPASS). 100%
ordinarily corresponds to 75 kHz-carrier deviation.
Note that if the 5750's subcarrier inputs are used, the meter will not indicate the subcarriers' effect on composite
modulation because the subcarriers are mixed into the composite signal in the analog domain, after the composite
signal is metered. Therefore, you must mentally add the subcarriers to the meter indication or refer to an external,
calibrated modulation monitor.
BS.1770 Loudness Level
Figure 6-4: BS.1770 Loudness Meter Block Diagram (from ITU-R document)
The subjective loudness meters, labeled LOUDNESS in the 5750's GUI, display the loudness at the output of the
digital radio processing chain and analog FM processing chains, measured by the ITU-R BS.1770-3 algorithm.
Recommendation ITU-R BS.1770-3 (08/2012): "Algorithms to measure audio programme loudness and true-peak
audio level." BS.1770-3 first introduced gating to the loudness meter. For further information about the BS.1770-3
meter, please refer to the following standards: ITU-R BS.1770, ATSC A/85 EBU R 128, EBU Tech 3341, EBU.
The loudness meter indicates both BS.1770 Short-Term and Integrated Loudness on the same scale. The solid bar
indicates the Integrated Loudness, while the floating bar segment indicates the Short-Term Loudness. Per the
BS.1770-3 specification, the integration time of the Short-Term Meter is always 3 seconds, while the Integrated
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