Operator’s Guide
9
Managing Microphones
– Your goal as sound operator is to provide sufficient,
quality sound from all program participants, to all in your audience. We’ve
prepared this section to help you do this.
Your sound system allows participants to speak naturally or even softly
as their material requires, confident that the audience hears every word
clearly. To do this, the power of the sound coming from the loudspeakers
greatly exceeds that picked up by the microphones. However, this advantage is
also a liability: When one or more microphones receive enough of their own
amplified sound from the auditorium loudspeakers, the result is that familiar
“howl” often called, “feedback”. Strictly speaking, a measure of feedback
occurs even when not enough for a full-blown “howl”. Lesser amounts of
feedback can result in a hollow sound, as if your participants were speaking
into an oil drum. Pros call this effect,
ringing.
Your audience finds this effect
distracting and tiresome.
If you turn your mics down to zero, you guarantee no feedback and no
ringing – but no benefit as well. As you increase your mic controls, the
audience gets to hear more of the program, as amplified sound overcomes
background noises. The sound becomes louder than your participants could
provide alone – your system is producing “gain.” In fact, the expression,
“raising the gain” simply means turning up your mic controls.
This graph shows that as you
turn up the mics, the desired
sound (blue line) steadily
increases and the audience
hears better. At first, the bad
effects of feedback (red) are
minimal. Increase gain beyond
a certain point, however, and
feedback multiplies. Once
ringing is heard, you must
reduce
gain to achieve clear,
usable sound. The dotted
lines show when gain is set
properly – enough sound while feedback remains inaudible.
Gain
Sound
Ideal level
Quality
Sound
Feed-
back