BCA Show Preview - 46

46

SUNTEC SINGAPORE

A part of

SHOW PREVIEW | 26-28 June 2018

MARINA BAY SANDS * SUNTEC SINGAPORE

Broadcast Audio
Processing Strategies
Orban's Peter Lee asks: Have you ever been frustrated trying to get the desired sound
for your station? Have you ever said: "I'll know its right when I hear it," but were at a
loss to achieve that sound? Sometimes it's difficult to get the on-air sound you want...

T

his article aims to provide a general
guideline to managing the sound of your
station to get the results you want. This
guideline won't focus on any specific model
of audio processor considering the variety of
processing in use, both old and new. Neither
will this article tell you how your station should
sound. Instead, this proposes a systematic
approach for getting the desired results.
Tuning a station's audio processing requires
a demanding combination of artistic judgment
and technical experience. The basic approach
is finding your preferred sound incrementally,
usually by adjusting past the optimum tuning
point, and then retreating, or "backing it off".
In other words, the idea is that you won't
know that you've arrived until you went too
far. Chances are unlikely that the first pass
of adjustments will meet your objective. So,
employ a progressive approach. Take small
steps toward the goal, rather than attempting
one huge leap since the latter is too complex
to manage and almost certain to fail.

Subjectivity
If the general manager, programme director
and engineer have divergent preferences,
define who will be the ultimate judge. This is
an opportunity for positive interdepartmental
teamwork. Unfortunately, it's also an
opportunity for sharp division. Secure the
best outcome by uniting all players toward a
common objective.
Encourage use of audience research.
Research is much more reliable than
depending on the preferences of one (or a
few) individuals.

The Desired Result
There is one "right" answer - the processing
that maximises your target audience.
However, in practise it's almost never
possible to define precisely what that
processing is, even with audience research.
Almost all processing is therefore adjusted
partly by gut feel, relying on the preferences
and experience of those responsible for the
station's sound, and, preferably, by adding
research to the variables used to make the
decision. At one end of the scale is minimal
processing for an on-air sound that is most
faithful to the original recording.

On the other end of the scale is aggressive
processing that may sound quite different
from the original source. Is your target
audience aged 40 to 54 listening on a home
audiophile system, or 20 something and
listening in the car, or perhaps women in
their 30's listening in the office? Each of
these cases has appropriate types of audio
processing. Moreover, the most appropriate
processing for your audience may change for
different parts of the day.
Good judgment is the rule. By comparison,
it's much easier to tune the RF section of a
transmitter since there's an objective meter
indication when tuning is ideal. There is
no meter indication of when processing
is "in tune"; you must rely on your artistic
judgment. Deciding on, and defining, the ideal
point on the scale is perhaps the most difficult
task in meeting your objective.
Legal limitations restrict peak modulation.
Peak modulation and perceived loudness are
not alike. A minimally processed Classical
format can have similar modulation peaks as
an aggressively processed Hot Urban format
though the latter will sound much louder.
Increasing loudness by simply cranking
the modulation invites legal penalties; more
effective alternatives exist.
Align your processing objectives to
complement the overall audience, format
and business plan. If increased time spent
listening is a priority for your station's ratings,
aggressive processing for dial dominance is
not appropriate. But CHR and Urban formats
can often benefit from a highly processed
sound that increases the energy level of the
presentation. Compression and equalisation
can do this; there's no reason to make
the sound overtly distorted and grungy by
excessive clipping.

System Considerations
No audio processor can repair source
audio that is noisy, distorted, excessively
bit-rate reduced, or suffers other maladies.

Aggressive audio processing exaggerates
any defects in the source material seen by the
processor. If the unprocessed audio is faulty
so follows your on-air product.
More audio processing components
installed in your system does not guarantee
better sounding audio. It does however;
guarantee greater difficulty in managing the
audio processing to achieve the desired
result. Adding components increases risk
of failure and often, degrades the audio.
Changes made to the first component
cause downstream components to react in
sometimes-unpredictable ways. In general,
it's wise to minimise components in the
audio chain. Peak overshoot is the enemy
of perceived loudness. Every percent of
overshoot broadcast is about 0.1dB of
loudness sacrificed. Therefore, every
component in the system following and
including the broadcast audio processor must
have the lowest possible overshoot.
Probably the best measure of an audio
processor's performance is how effectively it
can reduce the peak-to-average ratio without
introducing unpleasant artefacts. In other
words, how well it can increase perceived
loudness without pumping the audio, sucking
up noise, creating weird frequency balances,
or adding objectionable graininess or
intermodulation distortion due to excessive
clipping.

Configuration
Components in the system must be
arranged to deliver the best peak control
possible (i.e., minimum overshoot) to the
transmitter.
A common problem is locating the main
audio processor prior to an overshooting
studio to transmitter link (STL); if the audio
with overshoot is applied directly to the
transmitter, you must reduce modulation
(and loudness) to remain legal. Two
common solutions are to relocate the main
audio processor after the STL, or to fix

the overshoot problem in the STL itself.
While some newer exciters have built-in
overshoot limiters, use these only as a last
resort. Moreover, composite clipping is not
appropriate as a cure for overshooting STLs
because it adds audible non-linear distortion
and can interfere with SCAs and the stereo
pilot tone.
Receivers differ. What sounds great on
a US$3000 receiver will not sound the
same on a US$100 boom box. Act upon
the broadcasting system as a whole: from
the studios to the audience, through the
lens of the processing components-STL
transmitter-receiver.
Listen in varied environments: in your car
(or pickup truck), in the office on table radios,
with personal "Walkman" style radios...
whatever is typical to your audience.
In addition, if your target audience
typically listens at low volume, it's wise
to do the same. It is irrelevant to evaluate
audio processing with a pair of US$2000
loudspeakers if your target demographic is 12
to 18 year-olds. It's prudent to have a highquality monitoring system as a reference,
however keep things in the context of the
target audience.

Start Tweaking
Where to start? It doesn't matter whether
you're walking in "cold" or correcting an
ongoing problem.
You most likely will have a digital processor,
try one or more of the manufacturer's
recommended presets as a starting point.
Some digital processors like the OPTIMOD
have the added advantage of a single
control that scales many parameters to your
preference, making the task of adjustment
much easier.
What to tweak. Make an effort to understand
the operation of your audio processor(s).
Study the operating manual(s). Understand
the effect of each adjustment. Adjusting the
AGC probably shouldn't be your first choice
Orban 5500
https://www.orban.com/overview-optimodfm5500i
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