What is in this article?:
- The Forum: Comparing loudness meters, part 2
- Problems with low peak-to-RMS ratio material
- Studies indicating that BS.1770 is inaccurate at very low frequencies
- Discussion and conclusions
This article is the second and concluding part of an article in our Broadcast Forum focusing on an examination of loudness and measurement. Part 1 may be found in the August issue.
We continue our discussion with an examination of the results after automatic loudness control. Figures 1 and 2 summarize that data. (To present the data with optimum graphic resolution, the loudness scales are narrower than in last month’s graphs.)
Both the loudness vs. time graphs and the histograms show the Orban 8685 controls loudness well, although the details of the meters’ indications are different. Both the BS.1770 and CBS measurements indicate that most of the data points are in a ±1dB/LK window.
The peak CBS readings fit within a ±2dB window. The BS.1770 readings also fit within a ±2 LK window — except for four short intervals, which appear as low-probability outliers in the left side of the histogram. These intervals correspond to dialog without background music and in the author’s opinion illustrate a weakness in BS.1770-2: Based on our extensive listening tests, we have concluded that the meter does not effectively lock onto the A/85 “anchor element” (almost entirely dialog in the test material used to prepare this paper) and instead indicates that loudness increases when dialog level is held constant while underscoring or effects are added to the mix.10