What is the directivity of a microphone?
Microphone directivity refers to sounds coming from different directions when the microphone is picked up. There are two openings at both ends of the directional microphone's pickup diaphragm. According to the classification of polar coordinates, the sound picked up from the front is more sensitive than the sound from the back. The vibration depends on the phase relationship, which depends on the pressure difference between the two sides. . The responsibility of the microphone is to transform the physical sound signal into an electrical signal that can be controlled electronically, but the mode of sound pickup has a significant impact on this conversion process, whether in the field or in the recording studio. In the recording room, you can use microphones with different characteristics to record different effects.
The cardioid pointing mode is our first choice when choosing a unidirectional microphone (which can only pick up sound in one direction). As the name suggests, its pointing pattern is similar to the shape of the heart when it is represented by graphics. This makes the microphone very sensitive to the sound directly in front, while the sound from other directions can be well isolated. In the studio, the use of cardioid microphones can effectively reduce surround sound and reflected sound microphones. This can help you record good sound in unsatisfactory environments.
Each point microphone (cardioid, supercardioid) has a so-called proximity effect. When the microphone is close to the sound source, the low-frequency response increases, so the sound is fuller, leading to the proximity effect. Professional singers often use this effect. For singers, using this effect can create warmth and fullness of the sound. However, if the change in this effect is too obvious in a complete recording, it will cause problems. The timbre causes undesirable excessive changes.
Omnidirectional microphones are sensitive to sounds from all directions. Regardless of whether the sound is above, below, on both sides, behind or in front, the sound can be picked up evenly, but it is not picked up perfectly. However, it is a very effective tool in the studio, especially if you want to pick up all the room sounds! Another feature is that the omnidirectional microphone does not change with the change in the distance of more sound characteristics. In other words, even if the singer moves on the stage, the recorded sound will not change much, and the sound is natural.
The directivity of the super cardioid microphone is narrower than that of the cardioid, which is particularly suitable for close-range pickup. It is particularly suitable for fixed-point recording of drums and pianos, and its directional characteristics are very suitable for on-site recording that requires isolation (sometimes to isolate interference between instruments, and sometimes to isolate noise). For self-playing and self-singing performance recordings, the crosstalk of super-directional microphones is minimal. On the downside, for singers who are more active on the stage and like to dangle, the sound changes caused by the angle and distance of the movement will be correspondingly obvious. For the tuner, it is only necessary to control the volume and tone. More difficult to grasp. Another disadvantage is that the placement angle of this microphone, especially the bottom position, if it is slightly wrong, may cause serious feedback.
Figure eight pointing
The two-way mode microphone (also known as the "8-shaped" microphone) can pick up the sound on both sides very evenly. Because it is sensitive to sound, it is generally placed closer to the sound source (90° off-axis). But this is also a pickup mode that is not very useful in live music, and is more suitable for recording studio environments: it is used in some creative sound field arrangements. They get the picked up sound from the front and back, not from the side. If you use a figure-eight ribbon microphone to record human voices, you need to pay attention to the phase of the sound waves reflected in the microphone room. To record two singers, the figure-8 is very practical. You can make one singer in front of the microphone and the other behind, so that you can reduce the sound reflection in the room.