Microphone Types

• Definitions and Polar Patterns

• Wired

• Wireless

 

 

 

Definitions and Polar Patterns

A microphone or mic as they are often called, is an electro-mechanical device that converts acoustic sound waves into weak electrical signals. These very low level signals can then be amplified and heard through a loudspeaker, or recorded. Microphones come in many varieties, from small low cost types found in telephone handsets to large and expensive recording studio models. Microphones are classified by their directional pick up or polar patterns into two main categories, omnidirectional and cardioid. The pick up or polar pattern of a microphone refers to the directional angle at which the microphone is both most sensitive and least sensitive to the pick up of acoustical sound waves.

Omnidirectional or omni microphones pick up sound from all directions evenly, with a circular polar pattern. An omnidirectional microphone is an excellent choice for symphonic music recording because the audience and hall reverberation will be picked up equally along with the music, giving a very accurate (you are there) representation of a musical performance in a concert hall. It is precisely these highly accurate pick up characteristics that make an omnidirectional microphone a poor choice for speech or presentation use. An omnidirectional microphone will pick up the room reverberation, the sound system loudspeakers and the audience, as well as the primary person speaking.

Unidirectional or cardioid microphones pick up sound from the front while rejecting sound from the back and sides. The cardioid name comes from the heart shaped polar pattern. A cardioid microphone is the preferred choice for speech and presentation use because a cardioid microphone will pick up the primary person speaking, while rejecting room reverberation which increases intelligibility, the audience which avoids distraction, and the sound system loudspeakers which helps to minimize the potential for feedback.

For speech and presentation use, there are two major types of cardioid microphones available, wired and wireless.

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Wired Microphones

Wired microphones use a cable to carry the electrical signals from the microphone to a sound system or recording device.

Wired microphones are the first choice for most presenters, for several key reasons summarized below.

Advantages of Wired Microphones

No batteries required • Simple to use • High reliability • Low cost

Disadvantages of Wired Microphones

Cable limits mobility • Visually obtrusive due to size

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Wireless Microphones

A wireless microphone is actually a system that consists of two major parts, a microphone/transmitter and a receiver. The microphone/transmitter transmits the microphone signal via radio frequencies to the receiver, which is connected to a sound system or recording device. No wires or cables are used to directly connect the microphone to the sound system or recording device, thus the name wireless.

A wireless microphone, regardless of whether it is handheld or a clip-on style, will require a battery, typically a 9 volt plug in type. Presenters are advised to replace wireless microphone batteries before any important speech. Since 9 volt batteries are quite inexpensive, this is cheap insurance. Almost all wireless microphones have two switches, one switch to turn the transmitter on, and one switch to turn the microphone on. Both switches must be on for the microphone signal to be heard through a sound system. Because wireless microphone systems are more complex technically and operationally, wireless microphone systems are more prone to problems than wired microphones. The primary reason to use a wireless microphone is to have the freedom to move around a stage, meeting room or other presentation space. As shown below, a wireless microphone offers few advantages over a wired microphone for presentations that will be given from a stationary podium, which require little movement by the speaker.

Advantages of Wireless Microphones

Freedom from cable • Miniature models not visually obtrusive

Disadvantages of Wireless Microphones

Batteries required • Set up and use not simple • Lower reliability • High cost • Limited availability • Subject to interference

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