"Dave Plowman (News)" wrote in message
...
In article ,
Serge Auckland wrote:
As an aside, in radio, digital metering is still done on conventional
BBC style PPMs, which under-read by anything between 1-4dB depending on
the programme content.(some will say even up to 7dB) I and others have
tried persuading radio stations to use a true-peak meter, even if it is
calibrated with the familiar BBC 1-7 scale. The universal reaction was
that the signal was too quiet, and everyone prefered to go back to a
meter they were familiar with, even if it didn't tell the truth, and
rely on the 10dB headroom between the +8dBu UK peak operating level and
the +18dBu maximum to accomodate any unseen peaks. US practice is even
less precise as they still use VU meters and rely on the 20dB headroom
between 0VU (+4dBu) and their +24dBu=0dBFS.
The great beauty of the analogue PPM is that it gives a good indication of
perceived loudness as well as the electrical value. It's the Holy Grail to
find something which does this better - but it hasn't happened yet.
--
Dave Plowman London SW
To e-mail, change noise into sound.
It's relatively trivial to make a PPM with an LED analogue scale, arranged
in an arc if that's what's more familiar. The PPM's software can be set for
BBC dynamics, both rise and fall, or true-peak rise and conventional fall,
(or any other dynamics that you may care to think of). When we supplied
digital desks to various radio stations, we started with the PPMs indicating
true-peak rise, but within a week or two, the user always reset them to
mimic conventional mechanical pointer rise and fall. It seems that nobody's
actually interested in what the real levels are, just what it looks like -
as you say, they have a mental map of perceived loudness, and that's more
important than the actual level - after all, isn't 10dB headroom enough to
catch any nasties?
S.