Getting the right microphone is essential for sound engineering, there are many different types of microphones including wired and wireless and ones with different polar patterns (pick up areas). Microphones use magnetic induction (dynamic microphones) or capacitance change (condenser microphones) to change sound waves (air pressure vibrations) into electrical signals that are used through the process of pre-amps, analogue or digital desks and then loudspeakers where they are amplified.
Dynamic microphones contain a thin diaphragm and when the sound waves strike the diaphragm it vibrates against a metal coil causing electromagnetic induction creating a charge similar to the sound wave. This is a very cost effective way of replicating audio. They can handle extreme temperatures and rough handling and impossible to overload which is an important feature.
Condenser microphones use a diaphragm and an electrically charged back plate. This is basically a capacitor (device which can store a charge), and within an insulator separates the metal-coated back plate, which is rigid, and the diaphragm, which is flexible. When the condenser element is charged, an electrical field is created between the diaphragm and the back plate – an important point is that the charge is equal to the space between them. As sound waves strike the diaphragm and cause it to vibrate, the spacing in between the two surfaces varies, affecting the electrical charge in the capacitor. This fluctuation creates the electrical representation of the sound wave which is transmitted to the desk. There are two types of condenser microphones, the main difference is how the back plate is charged. Electret condenser microphones have a permanently charged back plate however Non-electret require an electrical supply to them and this is known as phantom power. In most cases the desk or stage box supplies phantom power which is 48Vdc and therefore it is sometimes known as adding in 48 volts. It is supplied directly through the microphone cable. Some electret condensers have means of supplying the power in case of a phantom power failure by means of a battery or a battery pack. Due to the complexity of their design and the circuitry required, condenser microphones can be considerably more expensive than dynamic microphones. They are also more sensitive to temperature and humidity changes or rough handling. However, condensers are more useful in certain areas; they are usually a lot smaller than dynamics making them a lot easier to hide! Secondly, they generally have much better frequency response and higher sensitivity therefore better for overhead microphone techniques where the microphones are placed much further away from the source of the sound.
Polar patterns indicate what areas the microphone is best at picking sound up at; the most common are Omnidirectional, Figure of Eight (Bi-Directional), Cardioid, Hyper-Cardioid and Line and Gradient (Shotgun). Each of these have different pick up areas and should be used for different sorts of things.
Dynamic microphones contain a thin diaphragm and when the sound waves strike the diaphragm it vibrates against a metal coil causing electromagnetic induction creating a charge similar to the sound wave. This is a very cost effective way of replicating audio. They can handle extreme temperatures and rough handling and impossible to overload which is an important feature.
Condenser microphones use a diaphragm and an electrically charged back plate. This is basically a capacitor (device which can store a charge), and within an insulator separates the metal-coated back plate, which is rigid, and the diaphragm, which is flexible. When the condenser element is charged, an electrical field is created between the diaphragm and the back plate – an important point is that the charge is equal to the space between them. As sound waves strike the diaphragm and cause it to vibrate, the spacing in between the two surfaces varies, affecting the electrical charge in the capacitor. This fluctuation creates the electrical representation of the sound wave which is transmitted to the desk. There are two types of condenser microphones, the main difference is how the back plate is charged. Electret condenser microphones have a permanently charged back plate however Non-electret require an electrical supply to them and this is known as phantom power. In most cases the desk or stage box supplies phantom power which is 48Vdc and therefore it is sometimes known as adding in 48 volts. It is supplied directly through the microphone cable. Some electret condensers have means of supplying the power in case of a phantom power failure by means of a battery or a battery pack. Due to the complexity of their design and the circuitry required, condenser microphones can be considerably more expensive than dynamic microphones. They are also more sensitive to temperature and humidity changes or rough handling. However, condensers are more useful in certain areas; they are usually a lot smaller than dynamics making them a lot easier to hide! Secondly, they generally have much better frequency response and higher sensitivity therefore better for overhead microphone techniques where the microphones are placed much further away from the source of the sound.
Polar patterns indicate what areas the microphone is best at picking sound up at; the most common are Omnidirectional, Figure of Eight (Bi-Directional), Cardioid, Hyper-Cardioid and Line and Gradient (Shotgun). Each of these have different pick up areas and should be used for different sorts of things.
- An Omnidirectional Microphone covers all areas and picks up sound in a 360 degrees radius; this makes them ideal for headset microphones, lapels and for simple handheld microphones. They are not sensitive to the wind and are less susceptible to popping noises (plosive sounds).
- A Figure of Eight Microphone will pick up sound from the front and back of the microphone and reject all sound that comes in from the side; this makes them ideal for use in duets, as studio microphones and in broadcasting.
- Cardioid Microphones pick up sound within a 120 degrees radius from the direction they are facing; due to this, they help to reduce feedback but they are susceptible to wind and popping noises (plosive sounds). The Cardioid design is achieved by putting an Omnidirectional Polar Pattern with a Figure of Eight Pattern.
- Hyper-Cardioid are very similar to Cardioid Microphones but pick up sound within a 100 degrees radius; this makes them extremely good at reducing feedback and have better side rejection than Cardioid Microphones. This makes them an ideal choice for a singer.
- Line and Gradient (Shotgun) microphones use a highly complex directional polar pattern; it works by having an interference tube in front of the capsule with small slits in the tube. It picks up sound from one direction only by eliminating sound from the side due to Phase cancellation. The longer the interference tube, the tighter the polar pattern and therefore the more directional it is. Shotgun microphones are brilliant for film and TV works as they do not have to be right by the sound source and therefore can be kept out the way of the camera.