A commonly heard complaint from broadcasters concerns the relative loudness of their DTV station in their market. In some cases, engineers are being requested to "match the loud station" and have raised objections to the request, and rightfully so. The symptoms of the problem may belie the actual problem. Surprisingly, it is very likely the case that the quieter stations are set correctly and the louder stations need to adjust their loudness downwards.
ATSC standards explicitly state that the dialog loudness of a program will be measured and set correctly using an LeqA (long term A-weighted loudness equivalent) meter or one that gives a substantially equivalent result. The FCC has passed these standards into federal rules, and as such they are the law of the land in the United States for terrestrial digital television.
In the simplest terms, this means that a standardized method and value for the loudness of a program is defined. This means that it should be a relatively straightforward procedure to measure and set the loudness of any DTV station. A standard modulation meter is of no use in digital television, and neither are standard VU, PPM, or other weighted meters unless they specifically support the LeqA method. Luckily, there are meters available to get the job done, but what exactly do they measure, and what gets adjusted to fix the problem? Stay tuned.
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