MICROPHONES

What are microphones? What are the different types of microphones? How do microphones work?

A microphone is a transducer that converts sound energy into electrical energy which is called audio . There are different microphones that work in different ways for recording different types of instruments. There are mainly two broad categories of microphones viz. dynamic and condenser.

DYNAMIC MICROPHONES

Dynamic microphones are the microphones that use a phenomenon called EMI (Electro Magnetic Induction) to convert sound energy into an electrical signal. An induction coil, placed in the magnetic field of a small permanent magnet, is being attached to the diaphragm. When a change in air pressure near the microphone causes the diaphragm to move, the coil starts moving as well in sympathy with the sound waves which then causes a change in the magnetic flux linked with the coil. As a result, an emf is induced in the coil which is termed as the audio signal . Moreover, some microphones have multiple diaphragm in order to record different frequencies in the frequency spectrum. For example, one diaphragm may have a better frequency response for the low end while the other may have the same for the high end or maybe the mid end. Hence, microphones with multiple diaphragm may be quite expensive but they solve different recording purposes like recording the kick drum that only has frequencies lying in the low end of the frequency spectrum.

Uses

These microphones have numerous uses viz. for a live gig, radio stations, recording vocals, and different instruments, live sound and many more.Dynamic microphones are very robust, relatively less expensive, can handle high SPL (Sound Pressure Level) and resistant to moisture, best suited for live purposes. However, they do not have a very good output level and frequency response.

CONDENSER MICROPHONES

Condenser microphones are another type of microphones that are also called capacitor microphones since they use capacitance for their functioning. In these microphones there are two plates which equally but oppositely charged and a diaphragm is attached to one of the plates of the capacitor. A constant potential difference is maintained across the two plates by using an external power source called phantom power. When a change in air pressure near the diaphragm occurs, the diaphragm starts moving in sympathy with the sound waves which the causes a change in the distance between the two plates of the capacitor. As a result, the capacitance linked between the plates changes and an Alternating Current is generated which is referred to as an audio signal. These microphones are used in recording vocals, recording instruments which do not have high SPL levels.

Uses

These microphones are more sensitive to higher SPL, have very good high and low-frequency response, have low noise and strong output level, have a various polar pattern, often have an inbuilt pad or HPF (High Pass Filter).

However, these microphones are quite expensive, more fragile than dynamic microphones, need phantom power, not suitable to all miking situations. These are used in recording vocals, drum overheads, acoustic instruments, guitar amplifiers, ambient room mics.

There are some other types of microphones like Ribbon microphone, shotgun microphone, etc.

RIBBON MICROPHONES

These microphones work in a way similar to that of dynamic microphones. These are similar to moving coil but uses a ribbon instead of a coil. The ribbon is very thin and corrugated. They also work on the principle of electromagnetic induction but in this case, ribbon disrupts the magnetic field instead of the coil. Ribbons have a relatively light moving parts which make them sensitive to high frequency.

Uses

They can be damaged easily by high SPL levels and have a relatively low output level. They have very low self-noise and have a good transient response. They are quite expensive, prone to wind noise and require phantom power. They are used in studio, radio shows, vocals (especially jazz music), strings, distance miking of brass.

SHOTGUN MICROPHONES

They can be either be dynamic or a condenser depending upon how they are manufactured. They have the most highly directional of simple first-order unidirectional types. At low-frequencies they have the classic polar response of a hypercardioid but at medium and higher frequencies an interference tube gives them an increased forward response. This is achieved by a process of cancellation of off-axis waves entering the longitudinal array of slots. A consequence of this technique is the presence of some rear lobes that vary in level and angle with frequency and can cause some coloration effects.

Uses

Due to the narrowness of their forward sensitivity, shotgun microphones are commonly used on television and film sets, in stadiums, and for field recording of wildlife.