The type and detection method of microphone

Last Update Time: 2018-12-28 15:10:51

Microphoneis a device that converts sound energy into an audio.

There are many types of microphone, the most widely used is the moving-coil simple and electret condenser microphone. The symbol for the microphone is " BM ".

1. The type and technical index of the moving-coil microphone


( 1 ) Moving-coil microphone consists of a permanent magnet, a sound film, and a voice coil, the voice coil is located in the gap of the permanent magnet and is stuck together with the sound film. When there is a sound, the sound wave excites the vibration of the sound film, drives the voice coil to make the cutting magnetic force line to move and produces the audio frequency induction voltage, so as to realize the acoustoelectric conversion.

The main technical parameters of the movable coil type simple tube are frequency response, sensitivity, output impedance, directivity and so on.

1)The frequency response range of the moving-coil microphone is obviously wider and the better, but the wider the frequency response range, the higher the price. The frequency response range of the ordinary moving-coil microphone is 100 ~ 10000Hz, and the frequency response range of the microphone with good quality can reach 20 ~ 20000Hz.


2)The sensitivity of the moving-coil microphone refers to the ability of the microphone to convert the sound signal into a voltage signal, which is expressed by the number of millivolts per Pascal sound pressure, its unit is mV / Pa. The sensitivity of the microphone is also commonly expressed in decibels ( dB ). In general, the higher the microphone sensitivity, the better the quality of the microphone.


3) The output impedance of the moving-coil microphone is of high impedance and low impedance. The output impedance of the high impedance microphone is 20kilo-ohm, and the output impedance of the low resistance microphone is 600 ohm, which is used in conjunction with the transmission impedance of the amplifier. Generally, after purchasing the amplifier, the corresponding microphone is purchased according to the impedance of the amplifier.

4)The directivity of the moving-coil microphone refers to the sensitivity of the microphone and the characteristics of the acoustic direction. The directivity of the microphone is designed according to the needs, and it is divided into all-directional microphone, one-way directional microphone, two-way directional microphone and near-speaking microphone. The all-directional microphone has the same sensitivity as the sound from all sides. The sensitivity of the one-way directional microphone is significantly higher than that of the back and side. Two-way directional microphone has the same sensitivity on the front and back, and the sensitivity on both sides is relatively low. Near speaking, the microphone only has a high sensitivity to the sound near the microphone, which is not sensitive to the distant environment noise, which is mostly used by singers on stage and singing.


(2)The detection of the moving coil microphone is mainly based on the electric barrier of the multimeter, secondary coil and coil.

First, use two stylus to touch the two leads, and the microphone should give out a clear " Kaka " sound. If it is silent, it means that there is a fault in the speech, and the various coils of the microphone should be further checked. ne should be further checked.

To measure the secondary coil of the output transformer, it can be measured directly with the two surface pen to check the output end of the city. If there is a certain value, the secondary coil is good, and the primary coil and the coil of the transformer are connected.

When the primary and sound coil coils of the output transformer are checked, it is necessary to disassemble the words and disconnect the primary and sound coil of the output transformer, and then measure the interruption of the primary coil and the coil coil of the output transformer.


2. Electret capacitive microphone

(1) the structure and type of the electret capacitive microphone

Electret is a new type of microphone made of electret material. It has the characteristics of small size, wide band, small noise and high sensitivity. It is widely used in hearing aids, recording machines, wireless microphone and other products.

The electret microphone is composed of an acoustic electric conversion system and a field effect transistor amplifier.


The electret condenser microphone is composed of a capacitor equivalent to an electrode position and a junction field effect transistor amplifier. When the sound wave is transmitted, the position of the capacitor changes, which is equivalent to the change of the capacitance, while the electric quantity on the two pole of the capacitor keeps certain, then the voltage at both ends of the capacitor changes, thus the sound and electricity conversion is realized. The Junction FET amplifier amplifies the signal voltage and achieves impedance matching with the amplifier in the amplifier.

The electret capacitance type has three types: two ends and two ends. The two ended electret capacitance type has 2 output terminals, namely the drain and the ground end of the field effect transistor. The three terminal electret capacitance type has 3 output terminals, namely the drain, the source and the ground end of the field effect transistor.

(2) Detection of electret capacitive microphone

The multimeter is placed in the RX100 gear, the black pencil case receiver's drain (D), the red surface pen receiver's source (S) and the shell (ground), and the mouthpiece to observe the instructions of the multimeter, indicating that the microphone is invalid if it is not indicated; with instructions, the microphone is normal. The greater the range of the indicator, the higher the microphone sensitivity. The detection of electret condenser microphone can be detected by the resistance meter of multimeter. For the two end electret capacitive microphone, the D end of the microphone is connected with a black pen, and the red pen is connected to the end of the ground,it will has aindication.

Compared with the same type of microphone, the larger the indication range, the higher the sensitivity of the microphone. If there is no indication, the microphone has a problem.


3. Wireless microphone

 ( 1 ) The structure of a wireless microphone is actually a combination of a general microphone and a wireless transmitter, operating at a frequency of 88 to 108 MHz in the FM band, they can be received by ordinary FM radio. The wireless microphone consists of a receiver, a modulation transmitting circuit, an antenna, and a battery. The sound signal is converted to the Telecom number by the sound head, and then transmitted through the modulation, and the corresponding receiver receives, amplifies and demodulates the sound amplifying device. The transmitting distance of the wireless microphone is generally less than 100m.


If you want to know more, our website has product specifications for the microphones, you can go to Allicdata Electronics Limited to get more information


SPU0410LR5H-QB-7 Allicdata Electronics