Introduction to Computer Music: Volume One

3. Microphones


Microphones are a type of transducer, turning minute changes in air pressure into equivalent fluctuations of electrical current. They are in some sense the opposite of loudspeakers, which do the same in reverse. In fact, if you were stranded on a desert isle with only a speaker, you could use it as a microphone, mimicking a moving coil type of mic. Composers, while not needing the same level of expertise in mic'ing that audio engineers might, need to learn as much as possible if they are recording samples for their compositions. Poorly recorded sound files only get worse when manipulated during the compositional process — you cannot erase excessive room ambience, or distortion, or phase cancellation caused by poor time alignment, or the choice of the wrong mic pattern for that particular task. Below, we will discuss some of the basics of microphones and mic'ing techniques.

Parts of a microphone

Body: holds all the components listed below, as well as the connector (usually male XLR for pro mics)

Diaphragm: the microphone equivalent of your eardrum, in that it is a small (.2" to 2"), usually circular-shaped piece of thin material (such as Mylar) that vibrates sympathetically with sound waves hitting it. It is either part of the transducing mechanism that produces electrical signals, such as in the case of a condenser mic, or it is physically attached to something else that produces the fluctuating current, as in a moving coil microphone.

Capsule: sometimes called an element, the capsule holds the diaphragm, screen, and electronics and physical isolators. Some microphones are sold with two or more interchangeable capsules for different response patterns.

Ports or vents: the opening in the microphone to let the sound waves in. While most microphones are described as front address — meaning the diaphragm is perpendicular to the front of the microphone, and the front of the microphone is pointed toward the source — some microphones, particularly those designed for stereo pairing, are side address, where the diaphragm is parallel to the sides, and vents are located on one or both sides of the microphone. The studio's AKG 414's are side address, meaning they can receive sound from both sides.

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