The three basic directivity of a microphone:
2. 8-character orientation
3. Heart-shaped pointing
1: Omnidirectional-sensitive to the sound of the entire red area.
2: Figure 8-Sensitive to the front and back areas where the two blues are located, while the left and right sides can be ignored.
3: Heart-shaped-sensitive to the green area in the front, slightly weaker on the sides, and negligible in the back.
Omnidirectional microphones were originally called "pressure" microphones. Their diaphragm measures the pressure of sound at a single point in space. Since they cannot provide location information, they are equally sensitive to sounds in all directions.
An omnidirectional microphone has the same sensitivity to all angles, which means it can pick up sound evenly from all directions, so the microphone does not have to point in a certain direction.
Figure 8 microphone
Usually called "pressure gradient" (pressure gradient) microphones, they measure the pressure changes on both sides of an open diaphragm unit. They are very sensitive to the sound in the front and rear areas, but almost shield the sound on both sides.
The figure-eight type is also called two-way type. This kind of pickup mode is special. It picks up the sound from the front and back of the microphone, but not from the side (90 degree angle).
It is usually a "stunt" held by an aluminum ribbon or large diaphragm microphone. It is also a necessary skill for many stereo and surround sound recording systems.
The birth of the heart-shaped pointing
In the end, someone suddenly wanted to combine the omnidirectional and the figure-of-eight direction, so they got the standard heart-shaped direction that we are familiar with today.
The cardioid microphone has the strongest front-end sensitivity and the weakest back-end sensitivity. In this way, unnecessary environmental noise can be isolated, and the effect of eliminating echo is better than that of omnidirectional.
Later, engineers designed a new heart-shaped pickup unit that combined the original structure. Soon there was a new direction: super-cardioid/"strong" super-cardioid.
Super Cardioid/"Strong" Super Cardioid
Someone realizes that if more 8-shaped signals are added and the omnidirectional signal is weakened, the directivity will be more prominent. The side effect is that it will produce a bulb-shaped sensitive area at the rear.
This new directivity is called a supercardioid, and the narrower version is called a "strong" supercardioid.
Compared to cardioid, supercardioid can cancel out more sound from the side of the microphone. It is more commonly used in the multitrack recording of chamber music to reduce the sound from other nearby instruments. It is also often used in live sound reinforcement, which reduces the risk of a lot of feedback sound whistling. The super cardioid microphone is most suitable for picking up a single sound source in a noisy environment and can most effectively eliminate echo.
When to point with a heart shape
The advantage of cardioid pointing is obvious. It picks up the sound of the area you are pointing at and ignores other sounds. It is especially suitable for the following situations:
Recording drum kit-With so many components close together, it seems impossible to isolate one by one. But it can be achieved by using the right heart-shaped pointing wheat and the correct position and angle.
Live performance-On the stage, the sound comes from all directions, and the heart-shaped pointing can play a good isolation role and prevent feedback.
Poor sound field environment-In a room with a poor sound field, using a cardioid pointing microphone at close range helps to reduce the pickup of reflected sound.
When to use omnidirectional
Because it is too easy to leak the sound, the usage rate of the omnidirectional microphone has been much lower after the cardioid point. But it still has a place:
Pick up the ambient sound of the room-such as a microphone that picks up the overall drum set;
Pick up a wide range of sound sources-such as a wind band, chorus, or grand piano;
Pick up a moving target-such as an acoustic guitarist who is sitting still;
Use stereo recording-such as common A/B technology;
When to use figure eight pointing
The use of figure-eight pointing microphones is usually due to the following 3 situations:
For stereo recording
Use ribbon microphone
In order to maximize the isolation of off-axis sound