Saturday, December 3, 2011

Microphone Patterns and Characteristics


I write a few microphone reviews for this blog, but have never explained the microphone polar pattern terms I use, so I had better remedy this.

Of course, all microphones are sensitive to sound, but they have different designs that allow them to detect sound from different directions. This is called directionality, which can be sorted into two popular types:

- Omnidirectional, which detect sound equally from all directions.

- Unidirectional, which detect sound mostly from one direction.

We are going to look at these two types of directionality, as well as look at the polar patterns for popular microphone types. Polar patterns help visualize how the microphone picks up sound, and are usually included in manufacturer’s sales and support materials.

As omnidirectional microphones detect sound from all directions, they are good for general field recording where the inclusion of ambient sound is desirable. They are also handy if the target sound is moving and the microphone cannot be moved. Omnidirectional microphones are usually not the right choice for live sound, as background noise can become overwhelming. One notable exception is the Green Bullet harmonica microphone, which is killer in live situations.

Unidirectional microphones are the most popular type for live sound and handheld applications, as they reduce background noise and feedback. There are two popular unidirectional microphone types: cardioid and hypercardioid.

Cardioid microphones pick up sound mostly from the front, with some sound picked up from the sides and very little from the rear. It does not pick up solely from the front, as that would leave very little latitude for movement, and eliminating all ambient sound makes for a sterile tone. The Shure SM-57 and SM-58 are cardioids microphones. By the way, it is called a cardioid pattern because it is kind of heart-shaped, believe it or not.

Hypercardioid microphones (also known as shotgun microphones) have a smaller pattern, so that they are even more directional than the cardioid type. I think the pattern looks like an alien’s head. These microphones are good if you need to isolate more background sound, but they can sound unnatural. Also, if the microphone is not directed at the sound source, or if the sound source moves, there can be drastic drops in volume. I call this the “Huell Howser” syndrome. If you have ever seen him use a hand-held microphone, you will understand what I am getting at here.

Anyway, If you do not have a specific reason to get an omnidirectional or hypercardioid microphone for a live application I would avoid them, as there are more downsides than upsides to choosing them. If you are heading out to buy a microphone for general use in for your band or DJ application, a cardioid microphone will probably be your best choice.


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