Cardioid Microphones are microphones primarily used for picking up sounds with high gain from the front and sides but poorly from the rear. Their name comes from the fact that their directional sound pick-up is roughly heart-shaped in nature. Cardioid microphones are most sensitive to sound arriving on-axis, from directly in front of the microphone. They are still relatively sensitive to their sides (as above so below), at 90 and 270 degrees. Additionally, they have a null point (the angle of sensitivity, or most rejection) at 180 degrees, directly behind the microphone.
We can distinguish a few types of cardioid microphones from which are:
They are less sensitive to the sound coming from the sides (and above and below) than cardioid microphones-although they still exhibit some pickup from the sides, above and below. This makes them more directional-they do focus more on sound directly in front, and reject more off-axis sound than a cardioid microphone. An unavoidable trade-off of the hyper-cardioid pattern is an area of slight sensitivity at 180 degrees, directly behind the microphone. This means the null points are 35 and 45 degrees displaced from the rear of the microphone.
They are picking up sound coming from all directions more evenly. Furthermore, graphic resembling the shape of a circle typically represents them. However, all microphones become more directional at higher frequencies. So, it is still important to point an omnidirectional microphone in the right direction, on axis to the sound source. An omnidirectional microphone will pick up more spill (sound from adjacent sound sources, not really intended to go into the microphone) and off-axis room reflections than a directional microphone. This additional spill may or maybe not desirable-it depends on the source, in the role of the mix, the room, the type of project, and the desired production and mix style. Omnidirectional microphones have more open and transparent sound than directional microphones and can generally be positioned closer to sound sources than directional microphones, without sounding boomy or muddy.
Wide Cardioid microphones
They are typically less directional than cardioids but more directional than omnidirectional microphones. They favor sound coming from the hemisphere in front of the microphone. Moreover, they are more equally sensitive to sound coming from the sides (and above and below). Their null point is region directly behind the microphone. Also, their image usually represents a polar pattern. Their sound tends to be a balance of the openness of omnidirectional microphones, with some of the directional control of cardioid microphones.
Additional resources & source texts