Digital Music Interactions: Microphones

Digital Music Interactions
A software-based interactive music and performance system

Microphones

One of the most exciting parts of computer music is the interaction between human performer and computer system. As musicians, we have developed a large number of instruments, each with their own distinct sound and performance practice. While new technologies such as MIDI have emerged that allow new methods of musical communication between performer and computer, most musicians would rather perform on traditional instruments than on some relatively strange instrument-like controller. Therefore, if we want to create an interaction between performers on traditional acoustic instruments, we need some method of translating the sound of an instrument into a signal that a computer can understand. For this purpose, we use a microphone.

Microphones act as a bridge between the sound waves that we can hear, and the representation of these soundwaves in a form that can be understood by a computer. By translating the vibrations made by sound waves as they strike the microphone into electrical voltages, a microphone is able to capture the characteristics of a sound wave and either send it to be analyzed or modified in a computer or effects processor, send it to be recorded to tape or some other form of media, or simply make it louder, or amplify it.

For the Digital Music Interactions project, microphones allow the computer to hear what the performer is playing. Depending on which piece is being performed, the microphone may be used to record small sections of the live performance, to feed audio input directly into an effects processor, or simply to boost the signal of the instrument and play it back through a speaker system.

While there are many different kinds of microphones that use different technologies to capture sound waves, there are certain features that most microphones will have in common:

Connectors All microphones must somehow be connected to the computer or sound system being used. If a microphone is being connected directly to the computer, with no mixing-board or other interface in between, then it will use a thin connector similar in shape to the small connector, known as a stereo-connector most commonly used on headphones for portable music players (such as portable tape players, cd players, or mp3 players). If the computer being used has a sound card with an "audio-in" port (which commonly uses a port the same size as the stereo-connector, then the microphone can be connected to that port directly. If the microphone is first connected to an audio interface or mixing-board, which is then in turn connected to the computer, the microphone may use a larger connector, of which there are two very common types. The first type looks like the stereo-connector but is larger; this is called a 1/4-inch connector. This connector looks like the connectors found on standard guitar cables. The second type of connector is called an XLR connector. This connector has three prongs within a metal or plastic wrapping. The XLR connector is the standard high-quality microphone connector used for professional and semi-professional uses.

Cables There will be a cable that runs from the microphone to either the computer or to a mixing-board or audio interface. Depending on the specific microphone you are using (which will use one of the connectors mentioned above), a different cable will be used to make the connection between microphone and computer. Some microphones have their own cables attached; most commonly, microphones that use the stereo-connector will have attached cables. Some microphones have an XLR connector built in which can be connected to a separate cable. That cable can have an XLR connector on one end and either an XLR or 1/4-inch connector on the other end.