TC electronic SDN BHD Loudness Radar Meter LM5D - Manual (Page 7)

PPM PAGE
Press the “PPM” key to bring up the PPM display, Fig 6. The PPM page is used to
inspect balance between channels, headroom, overload of channels etc.
Fig 6, PPM True-peak meter features.
Bargraph PPM meters are shown next to the round Current Loudness display, which is
identical to the Outer Ring of the Radar page. The True-peak meters operate
regardless of the status of the Run/Stop/Pause controls. Click on the bargraphs to
reset the peak history.
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The peak meters of LM5 display true-peak as specified in ITU-R BS.1770. True-peak
meters give a better indication of headroom and risk of distortion in downstream
equipment such as sample rate converters, data reduction systems and consumer
electronics than digital sample meters used e.g. in CD mastering.
Fig 7, PPM True-peak meter example showing Madonna’s Hung Up.
Note the extreme peak level way above 0 dBFS, which is typical of hyper-compressed
program. This track will distort heavily when played on a consumer CD player or if it’s
data reduced.
Note that the meter scale is extended above 0 dBFS. Most consumer equipment
distorts if you see readings above 0. With data reduced delivery, -3 dBFS should be
regarded as max level without too much distortion. To be on the safe side with regard
to broadcast linking and transmission, -6 dBFS should not be exceeded often. Please
remember that excessive peak level may generate noticeable distortion and listener
fatigue.
When you enter the PPM page, the bargraph meters show the highest peak level
registered since the Radar or Peak Level history was reset.