Review - General Microphone Techniques

Each of us has at some time experienced the painful results of poor microphone technique. One image that comes to mind is the enthusiastic soprano that clenches her microphone and pulls it in as close as she can, just as she attempts to hit that high C. This is a classic example of how not to use a microphone to its best advantage.

This article studies several examples of microphone applications and how to get the best results. These basics will help you deal with most situations.

The Podium Microphone

It is easy to develop poor microphone habits when using a podium microphone. Usually the talker overcomes feedback and intelligibility problems by pulling the gooseneck microphone forward (can you hear that familiar creaking?). This may increase the volume but it actually creates other problems.

Figure 1

Figure 1 illustrates how the talker's movement can cause volume changes. Figure 1A shows a talker positioned 1" from the microphone. If the talker backs away only 2", the apparent sound level drops in half. When measured, the level change would be about a 10 decibel drop.

Now look at the Figure 1B. If the talker is positioned 1 foot from the microphone and backs away the same 2", the change in level is only about 1 decibel lower. In a typical auditorium or gymnasium, no one would notice a change in the sound level.

HINT: It is commonly accepted that a 3 decibel change in sound level is the least change that can be heard by the average listener.

In fact, in Figure 1B, the talker would have to back away from the microphone another 2 feet in order for the level to drop by half. The 1-foot position gives the talker freedom of movement without sacrificing sound quality.

The rule: for every doubling of distance, the sound level will drop by 6 dB. Or, the sound level will drop to half as loud when the distance is increased about 3 times.

Another podium-microphone hint, do NOT use more than one podium microphone. Additional microphones will create many problems.

By the way, you don't have to tolerate those older, noisy gooseneck microphones. There is a new generation of miniature condenser microphones. These goosenecks can be adjusted with very little noise. Please let us know if you're interested.

Figure 2

P-Pop

Another problem can also be avoided by maintaining a reasonable distance from the microphone. Commonly referred to as "P-Pop," this familiar explosive sound is most noticeable when the talker's mouth is positioned between 1 and 3 inches from the microphone. Most P-Pop disappears when the talker is 6 or more inches from the microphone. P-Pop can also be reduced by lowering the microphone and pointing it more toward the ceiling (see Figure 2) so the sound goes over the microphone. Reciting "Peter Piper picked a peck ..." etc. can help determine an acceptable microphone position.

Proper Distance

Distance from the microphone can also affect the tonal quality of the talker. As the talker moves closer to the microphone, not only does the sound level get louder, but the bass response of many microphones also increases (an effect called bass boost or proximity effect). Many professionals use this to their advantage in order to make their voice sound rich and pronounced. But this effect can also create problems.

A Common School Problem

The sports announcer has an impossible job: to be heard clearly over a large crowd in a large, reverberant room. The only solution that seems to make sense is to get as close to the microphone as possible. The announcer's voice may get louder, but his voice also starts to sound "muddy" or "boomy" because of the increase in bass response. This effect makes the announcer's voice difficult to understand.

Figure 3

There are solutions if you wish to avoid the "muddy" sound. 1) Maintain a distance of 12 inches from the microphone and turn up the microphone level. However, this will probably not be a good solution since too much noise will also get picked up. 2) Choose a microphone that has the least proximity effect (Figure 3 shows a proximity effect curve). Many microphone manufacturers include a "proximity effect" curve in their spec sheet. A good example of a reduced proximity effect is the headset microphone. The microphone element is placed near the corner of the mouth. This type of microphone will provide the best gain-before-feedback, as well as the most consistent level regardless of head movement. Some headsets include a single earphone which provides the added benefit of a vocal monitor, especially outdoors where "echoes" can confuse the announcer.

The solutions suggested above deal with changing the distance to the microphone. But increasing the distance will not help if you have a problem with gain-before-feedback. A professional sound contractor can help you determine the source of your feedback problems. Call us if this has been a problem for you.

Handheld Technique

Let's return to the soprano with the piercing voice. Some simple techniques can greatly improve the sound quality. First, vocalists should be trained to overcome the tendency to pull the microphone closer when attempting to hit those high notes. At the same time, more intimate vocal passages can be more dramatic if the microphone is moved closer.

For proper microphone positioning, try this approach (refer to Figure 4): Your elbow and forearm should form a 45 degree angle. Spread your other hand out from your mouth as shown in the diagram. Then move the microphone in front of you to about where your little finger ends (Be sure to keep the same distance and angle in relationship to your body).

At this position, P-Pop will be minimal, proximity effect will be very slight, and small movements with the microphone will not be audibly noticeable. Suggestion: when anticipating a crescendo, simply pull the microphone further away. This will sound much smoother and more pleasant than if the microphone was held stationary.

Variations on this theme are acceptable. Simply avoid moving the microphone too close, and be sure to keep the microphone off-axis to the mouth. These techniques are not quickly learned. It takes practice to overcome bad habits.

About Lavaliers

Wearing wireless lavalier microphones with costumes for theatrical productions can present a problem. Here are some simple rules to follow:

1. Center the lavalier (left to right). If the lavalier is positioned to one side, the amplified voice will drop if the actor's head is turned away from the microphone. Naturally, the voice will get louder if the head is turned toward the microphone. This results in very inconsistent levels.
2. Using the same hand-spread technique discussed earlier, position the lavalier so it is at least a full hand spread from the mouth. This minimizes differences in distance from the mouth caused by head movement. Again, this will help keep levels consistent.
3. Avoid having the lavalier cable hang straight down. This increases cable noise. Instead, put a gentle bend in the cable near the microphone by bringing the cable back up through the microphone clip (as shown in Figure 5).
4. Hide the miniature lavalier microphone in the actor's hair or beard. The sound level will stay constant since the microphone moves with the head.

Figure 5

These tips will help you start solving those annoying sound system problems that can be so disruptive. Please call us for help. Our primary purpose is to provide professional solutions that improve your professional environment.

by Travis Ludwig © 1996 Internet Sound Institute (www.soundinstitute.com). This articles is for personal use only. Any commercial reproduction is not permitted without permission. To obtain permission, contact ISI at hopi@soundinstitute.com

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