Microphone Technique

It may seem like second nature to some to speak into a microphone. Others may look at the microphone with the same look you'd give a high-tension wire lying on the ground. The fact of the matter is that good microphone technique is important to produce a good podcast. Different mics have different pickup characteristics and different sensitivities, so you must use proper technique to get the best out of your mic.

The basic requirement is that the microphone be in front of the sound source, as close as possible, but not so close that the microphone distorts or picks up any noise, particularly from troublesome consonants such as the letters "p" and "b." These letters are known as plosives and can be quite problematic, because the burst of air that comes out of your mouth when you pronounce them can cause the microphone to "pop." This is audible as a loud pop or a "thunk" in your recording. You may be able to get rid of this noise later on using signal processing, but try to avoid them in the first place.

Plosives are created by letting out a big burst of air from your mouth. The pop occurs because the tiny diaphragm inside the microphone is overloaded. To avoid this, you can use a pop screen, which is a bit of foam or sheer material designed to break up the burst of air. Pop screens must be acoustically transparent, meaning that they should not muffle or distort the sound at all. Many handheld microphones have a pop screen built in, as shown in Figure 1. For other mics, you can buy foam pop screens that fit over the microphone or a pop shield that is placed in front of a microphone. All of these are very effective at reducing the incidence of microphone pops.


Figure 1: A pop screen

Tip In a pinch, you can create your own pop shield by stretching a piece of pantyhose over a coat hanger and placing it in front of your microphone.

Handheld mics
Handheld mics are generally dynamic, directional mics, which means that they are resistant to handling noise, and tend to pick up in one direction. Directional mics must be pointed at the source they're recording. That may seem obvious, but novices sometimes forget they're holding the mic. Their hand will drop to their side, completely oblivious to the microphone. For this reason, handheld mics are often better left to seasoned professionals.

Clip-on mics
Clip-on mics, also known as lavalier mics, are a great option for most podcasting applications. They're small and unobtrusive, so people often forget they're even wearing them. (This can be somewhat embarrassing when a guest or on-air talent attempts to walk away with the microphone still attached.) Clip-on mics come in both directional and omni pickup patterns. For interviewing applications, use omni-directional mics, because they provide better pickup when the person speaking turns his head from side to side. If you're using directional mics, the level can drop dramatically when the talent turns away from the mic. For that reason, microphone placement is important when using clip-on mics.

The placement of a clip-on mic is dependent on the pickup pattern of the microphone, the clothing the talent is wearing, and the placement of guests, as shown in Figure 2. If two people are facing each other, for example sitting across from one another at a table, the mics should ideally be placed centrally, about six inches below the speaker's chin. If two people are sitting side by side, the mics should be placed so that when they are talking the mics will be in the best possible position to pick up the signal.


Figure 2: Clip-on mic placement depends on the situation.

Studio mics
If you have the luxury of a studio setup for your podcasts, you can use high-quality studio microphones. These mics can be used only in studio settings because they are so sensitive. They are very susceptible to handling noise and therefore impractical for handheld or non-studio applications.

Studio mics are placed on mic stands and often in special suspension mounts that make them less sensitive to vibration. The mic should be positioned so that it points at the talent's mouth. Usually, you want to have the mic a little high and pointed slightly downward towards the user's mouth, as opposed to below them and pointing up. This helps prevent pops, because the burst of air tends to be aimed downward.

Many, but not all, studio mics are condenser mics. In fact, two of the most popular radio mics, the Shure SM-7 and the Electrovoice RE-20, are dynamic mics. Both of these mics are treasured because of their lack of proximity effect and their resistance to pops.