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.

Podcast: : Other types of microphones

All the microphones described previously will serve you well, but they're not the only mics suitable for podcasting. A number of specialized mics might be better suited for your podcast, depending on your situation.

Clip-on (Lavalier) mics
Clip-on mics are common in television news broadcast, because they're small and unobtrusive. This also can be an advantage in podcasting, particularly if your guest has little or no experience talking into a mic. Many folks can be intimidated by large broadcast mics. Clip-on mics are great because the guest can forget about the mic, relax, and give a good interview. Two great lavalier mics are shown in Figure 1.


Figure 1: Clip-on (lavalier) mics: ElectroVoice RE90L, Audio Technica AT803B

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Headset mics
Headset mics can be ideal for some applications. You often see them on tradeshow floors so that the speakers can use their hands and not worry about holding a microphone. The other reason they're useful is that the microphone is very close to the speaker's mouth, so very little background noise is picked up. Some headphones include a built-in microphone, which is handy in situations where you need to wear headphones and want the convenience of a headset mic.

Many, many headsets today are sold by numerous companies to work with your cell phone, your laptop, your PDA, and who knows what else. Many of these headsets are very cheaply made. If you want to go the headset route, stick to the professional models. Most microphone manufacturers make a headset model. Two good headset mics are shown in Figure 2.


Figure 2: Headset mics: Audio Technica ATM75CW, Shure WBH53B

Wireless mics
Wireless microphone technology has been around much longer than wireless connectivity has. A number of different standards and transmission methods exist. Wireless mic setups involve one or more wireless mics and receiver units that convert the wireless signal back into analog audio. Wireless can be pretty slick, but it can be pricey. Setups start at around $500 per single mic and go up from there. The other problem is that wireless systems are prone to interference. Also, wireless microphones run on batteries, and as we all know, batteries always run out right in the middle of the most important part of the interview, right?

PZM / boundary mics
Pressure zone microphones (PZM mics) are designed to be placed on a large flat surface. They're ideal for conference room tables or podiums. They're kind of cool because they don't look like mics, so folks tend to ignore them. An example of a PZM mic is shown in Figure 3. They're not going to give you the same performance as a quality handheld or clip-on mic, simply because they tend to be further from the people speaking. However, they can be useful in situations where it's not practical to put a microphone in front of every single speaker.



Figure 3: PZM mic: Crown PZM 185

USB mics
One of the most interesting recent developments has been the arrival of the USB microphone. USB mics have built-in digital audio conversion, so instead of connecting them to a mixing desk, you plug them directly into your workstation. All mixing and signal processing of your podcast must be done in your audio-editing software, because you aren't using external hardware. You also are limited by the number of USB ports your workstation has. However, if you're looking for the ultimate in portability, a USB mic may be ideal. A number of USB mics are available, including the ones shown in Figure 4.


Figure 4: USB mics: Samson CO1U, Blue Microphones Snowball, Sound Professionals USB Mic-1

If you're looking for the ultimate in portability, Sound Professionals makes a USB mic the size and shape of a small flash drive, which offers amazing quality for the money. While it doesn't offer the quality of a dedicated microphone placed in front of each person talking, it's an indispensable tool for the laptop warrior.