© Copyright 1997 by Dorrough
Recently, a number of "Dorrough
clone" meters have entered the marketplace. While emulation
may be a form of flattery, potential users should be aware that
there is a danger of some possible confusion. The essence of
the Dorrough Loudness Monitor is much more than a clever, multi-color
LED display. The extensive research necessary to produce an entirely
new concept in audio metering has resulted in a line of products
unique in the world. We hope that this material will help you
to understand the background and potential benefits of the Dorrough
concept to your recording, studio or broadcast environment.
It's basic human nature to use the established method of doing
something rather than taking a philosophical approach and rethinking
the basic concept of what it is one is about to do. In the world
of audio engineering, this is no exception. The decades-old traditional
approach of setting program levels based on analog meter movements
has been deeply ingrained in our brains since childhood. So much,
in fact, that the VU meter has become an icon for audio monitoring.
The reality of physics, however,
is at odds with this simplistic notion that the sum total of a
complex audio waveform, comprised of up to dozens of spectrally
unique signals, can neatly be displayed on an electro-mechanical
device closely related to the Boys Scout compass (a magetised needle
floating on a leaf in a pool of water).
Fortunately, today's audio engineer
is more enlightened. Engineering vocabularies now include staple
terms like transient response, risetime, compression, spectral
energy content, etc. Much of this increased awareness is due to
the fact that today's audio and video transmission mediums are
far more "technologically litigated" than ever. In short,
our "father's VU meter" isn't relevant any more.
While experts argue the point about "VU" vs. "PPM",
the most demanding recordists have already decided that neither
is adequate for recording audio at the cusp of the millennium.
Now, decades of research, and "in-the-trenches" experience
have, at long last, determined a true relationship between RMS
metering, integration time and peak-levels, finally delineating
this Practical Standard. The advent of the Integrated Circuit offered
an opportunity to apply this research to the creation of a compact
metering device that could perceive sound "dimensionally".
Many of the most prestigious media giants are already benefiting
from a new generation of meters endowed with this "Practical
Even in today's more enlightened world of audio engineering,
LEDs, Peak-Hold functions, combining VU and PPM into a single
meter face, still fail to address the basic problem that both
systems are based on old assumptions. Early audio engineers merely
listened for "best results" and fashioned a meter display
device to correlate with those desirable outcomes. By 1939 sufficient
experience with these correlations produced the "Standard
Calibration" or "Reference Level" sought through
a joint effort by CBS, NBC and Bell Telephone Labs. It was apparent,
right from the start, that the resulting audio metering devices
still required interpretation by the audio technician.
Audio engineers, since the
late 30's, used the "VU" meter as a basic yardstick
of levels. Experience told them that what they were seeing
on the gauge wasn't truly indicative of what they, or their
recording devices, were hearing. Going strictly by the meter
was only going to work if the recorded subject was a single,
male-baritone, who spoke in a flat monotone! The instant
an instrument, a female voice, background noise, or even
emotion was added to the mix, the "VU" fell short.