The Application of Microphone and Matters Needing Attention

- Oct 09, 2018-

(1) Before using the microphone, you should first understand the type and characteristics of the microphone. The microphone with a slightly lower static technical index and better transient characteristics is better than a microphone with higher static index and poor transient characteristics. Capacitive microphones should also pay attention to the need to add power.

(2) There should be no large reflective surfaces near the microphone position, such as walls, to avoid strong reflections that cause sound phase interference and destroy the naturalness of the sound. The position between the microphone and the speaker is also very important. It is generally required to place the microphone behind the speaker to avoid the radiation direction of the speaker.

(3) The connector of the microphone should be firm and reliable. The requirements for the welding of cassettes or large two-pin plugs, sockets and microphones as microphone connectors are very standard. The microphone must transmit the signal using a high quality shielded cable. Since the output signal of the microphone is very weak, noise will be generated once the interference signal is inserted. Therefore, the metal shielded cable must be used to transmit the signal, and one end of the shielded wire should be well connected to the outer casing of the microphone, and the other end should be connected to the outer casing of the audio device. The length of the shielded wire should also be as short as possible. Because the longer the microphone line, the larger the distributed capacitance, which not only causes interference signals, but also causes loss of vocal signals (especially treble). Generally speaking, when the unbalanced connection (single-core shielded wire) is used, the length of the microphone connection should not exceed 10m. If the connection must be lengthened, a balanced connection (that is, a double-core shielded wire) should be used to reduce external interference.

(4) The distance between the sound source and the microphone should be appropriate. When singing lyric songs, actors often close the microphone to the mouth to take full advantage of the near-talk effect and boost the bass. The distance between the microphone and the mouth can be between 1 and 20 cm. In order to improve the clarity of the speech, the microphone should be 20 to 30 cm away from the mouth, and even special low-frequency effects should be removed.

(5) Since most of the singing or speech uses a unidirectional microphone, it should be noted that the angle between the mouth and the central axis of the microphone affects the frequency characteristics of the picked-up sound signal. When singing, the angle between the mouth and the center axis of the microphone is 0°, and the frequency response characteristic of the microphone output is the best; the farther the mouth is from the central axis, the frequency characteristics are worse, the higher the treble loss, and the output voltage of the microphone is also reduced. . Generally, the heart-shaped microphone should have an angle of 45° between the mouth and the central axis, and should be kept within 30° for the strong directional microphone.

(6) A good vibration damping device. The sound pickup unit is fixed on the sleeve frame, and the high-grade microphone has a vibration damping device to prevent the microphone from vibrating noise due to vibration or to accidentally fall on the ground due to the microphone or to generate a strong sound impact due to the bump, thereby damaging the high-pitched unit of the power amplifier or the speaker. Commonly used damping devices include rubber vibration-damping brackets, rubber microphone clips, rubber microphone clip pads, and spring microphone clips. When using the handheld microphone, do not hold the microphone cover to avoid clogging the rear air intake hole, causing distortion and affecting the effect. When using a wireless microphone, its carrier frequency should avoid the frequency of local FM radio or wireless telephone communication to avoid crosstalk.

(7) Good anti-interference performance. There are inevitably some kinds of magnetic fields and electric fields in the sound field, such as air conditioners, power lines and static induction of the human body. As the sound pickup unit of the microphone, the small noise interference is amplified by the mixer and the power amplifier, and the sound is sent to the speaker to form a strong noise, which impairs the quality of the sound, so the microphone structure and the outer casing are required to be well shielded. Function, requires all metal structure, good anti-magnetic, use good shielding microphone wire.

(8) When using multiple microphones for pickup, first make the phases of the microphones consistent; for a sound source, if you need to use two or more microphones for monophonic pickup (such as conference pickup), Keep the microphones as close as possible, or keep the distance between each microphone and the sound source equal to avoid phase interference when adding; if you need 2 or more sound sources to pick up the sound, you should make each microphone The distance is greater than three times the distance between the sound source and the microphone (that is, the 3:1 rule is satisfied) to reduce the phase interference phenomenon when the signals are added.

(9) Pay attention to wind, vibration and moisture. Outdoor and outdoor performances should be windproof to prevent the wind from blowing metal mesh to produce whistling sound; dust in the air enters the microphone, affecting the cleanliness of the magnetic gap, causing distortion; near the microphone, the mouth shape is close to the microphone, and the moisture in the mouth damages the microphone. Use a dust-proof and moisture-proof cover for the diaphragm.

The structure of the microphone is relatively precise. The strong vibration not only makes the output of the microphone too large, but also makes the sound reinforcement system seriously overloaded, and it is easy to damage the mechanical structure, demagnetize the magnet, reduce the sensitivity, and make the voice coil and the magnetic circuit collide. So pay attention to anti-vibration. Especially for condenser microphones, condenser microphones should be turned off before moving. In addition, be careful not to use the method of blowing air or tapping the microphone by hand to audition. In the storage of the microphone, you should pay attention to moisture and keep it clean.

(10) The phase of the microphone. If a mixer has multiple microphone inputs at the same time, if two microphones have opposite phases, when the two microphone signals are sent to the mixer mixing circuit, the signals will cancel each other, and the sound will be reduced. Therefore, when multiple microphones are used, especially when a variety of different types of microphones are used at the same time, the phases of the microphones must be the same. Phase discrimination can be performed by the following method. First put the two microphones together, and receive a sound source at the same time, the sound is increased, indicating that the two microphones are in phase. If the sound is reduced, and the distortion occurs, the microphone is reversed. Adjust the wiring of one of the microphones to achieve the in-phase sound.



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