In general, the loudest parts of the unprocessed audio are commercials and promos, both network and local. These are anywhere from 5dB to 10dB (or LK) louder than the rest of the program material. This inconsistency was not a problem because the station in question was using an Orban automatic loudness controller on-air, which smoothed out loudness differences before its input.
While the general shapes of the CBS and BS.1770 loudness vs. time curves are similar, there were some significant differences. For example, at approximately 1250 seconds, the CBS measurement shows a sharp loudness spike that was caused by a network news report that was equalized to emphasize frequencies around 2kHz to 3kHz, where the ear is most sensitive. The BS.1770-2 measurement did not indicate this as being louder than the surrounding program material although to our ears, it clearly was.
Editor’s note: This Forum paper will conclude with “Part 2, Measured Results,” in the September issue of Broadcast Engineering magazine.
- The CALM Act applies only to U.S. broadcasters and cable providers.
- Jones, Bronwyn L.; Torick, Emil L., “A New Loudness Indicator for Use in Broadcasting,” J. SMPTE September 1981, pp. 772-777.
- This software is available for free download at http://orban.com/meter/.
- EBU – TECH 3343, “Practical guidelines for Production and Implementation in accordance with EBU R 128,” version 1 (February 2011), p. 29
- Riedmiller, J., Lyman, S., Robinson, C., “Intelligent program loudness measurement and control: what satisfies listeners?” AES Convention Paper 5900, 115th Convention (October 2003)
- Optimod-Surround 6585 and 8685, Optimod 6300 (with version 2.0 and higher software), and Optimod-PC 1101 and 1101E (with version 2.0 and higher software).
- For a further discussion of the CBS and BS.1770 technologies, see http://orban.com/meter/Technology.html. The ATSC A/85:2011 document also discusses the BS.1770 algorithm.
- PSI Plot: http://www.polysoftware.com/plot.htm
- Unfortunately, two terms for the same loudness units have been used in different standards documents. For convenience, we will use LK and LKFS (as used in ATSC A/85); these units are the same as LU and LUFS (used in EBU R 128 and BS.1770) respectively.
—Robert Orban is chief engineer, Orban.