Microphones are devices used to convert sounds into electrical signals. These devices, which are also called electromagnetic sensors or transducers, facilitate the conversion of energy into another form. In the case of a microphone, sounds are converted into electrical signals.
All microphones have a diaphragm, which is a thin material that vibrates when it comes in contact with sound waves. The material may be made of plastic, paper or aluminum. Whenever the diaphragm vibrates the other parts of the microphone also vibrate. These vibrations will be transformed into electrical signals that eventually become the acoustic signal or the sound.
Microphones can be grouped into two different categories. The first category is the kind of conversion technology used on the microphone. The second category is the intended application of the microphones. The kind of conversion technology used essentially refers to how sound is converted into electricity in the microphone, including dynamic, condenser, ribbon and crystal. The second area refers to how these microphones are used.
Since the electrical current generated by microphones is small, it will be necessary to use amplifiers to increase the signal it produces. The amplification of the signal is achieved through a number of ways. The first is to have amplifiers built into the microphone. The second way is to use an external amplifier to increase the sound produced by the microphone. Sound mixers can also be used to increase the signal since they also have their own amplifiers.
Dynamic microphones are all-around microphones that can be used for just about anything. They have an uncomplicated design and come with a small number of moving components. These microphones are durable and ideal for high volume levels. They do not have their own amplifier and have no batteries or external power. These microphones create sounds using a coil of wire and a magnet. The diaphragm of these microphones is connected to the coil. Whenever sound waves hit the diaphragm, the diaphragm will vibrate. When this happens the coil moves towards and away from the magnet, which creates current in the coil. The current is transmitted from the microphone through wires.
Condenser microphones feature a component called a capacitor that converts acoustic energy into electrical energy. The term condenser actually means capacitor. These types of microphones require an external power source or a battery. Due to this, these microphones generate stronger signals compared to dynamic microphones. Capacitors consist of two plates. The first plate is made of light material and is used as the diaphragm. When sound waves hit the diaphragm, it will start to vibrate. Due to this, the distance between the two plates will change, which changes the capacitance. However, the capacitor will only work when voltage is present, which makes an external power necessary.
Electret condenser microphones are microphones using a special kind of capacitor featuring a permanent charge using electret material. These materials are essentially polarized or permanently charged. Since it has a permanent charge, these types of condenser microphones do not require any external power source or battery. However, electret condenser microphones have a preamplifier that will require an external power source.
Ribbon microphones feature thin, wavy metal ribbons floating in a magnetic field. The ribbon is linked to the output of the microphone, and the electrical signal is produced by the vibrations within the magnetic field. Since the ribbon is open on both sides, ribbon microphones typically detect acoustic signals in a bi-directional pattern. Since ribbon microphones respond to air velocity instead of sound pressure, these microphones are also called velocity microphones. While these types of microphones may not be ideal for regular stereo recordings, they can be positioned horizontally to allow them to pick up sounds on both ends of the microphone. Older ribbon microphones had the tendency to be damaged since it was necessary to suspend the ribbon loosely. However, modern ribbon microphones are made of durable materials that make them resistant to sudden wind drafts.
Crystal microphones are also called Piezoelectric microphones. Vibrations are converted by these microphones into electric signals through piezoelectricity. Piezoelectricity is the capability of materials to generate electrical energy when they go through pressure. Crystal microphones are normally used in amplifying sounds generate by acoustic musical instruments as well as to record sounds in extreme environments.