1. Carbon particle microphone
Carbon particle microphones have a narrow frequency response range, low impedance, and are easily distorted. At present, only some telephones are still using this type of microphone.
2. Crystal and ceramic microphones (piezoelectric microphones)
The frequency response is good (80Hz～7kHz), the impedance is high, the output level is high, and the price is low.
3. Condenser microphone
The condenser microphone is composed of three parts: pole, preamplifier and power supply (as shown in Figure 1). The pole is composed of a diaphragm and a plate. The diaphragm is an electrode of the capacitor, making it a simple capacitor. When the sound wave in the sound field makes the diaphragm vibrate, the distance between the diaphragm and the fixed rear plate changes, so that the capacitance also changes. This changing capacitance generates an AC voltage that changes with the sound pressure when it passes through the load resistance. The built-in preamplifier amplifies the output signal voltage. The advantages of condenser microphones: good frequency characteristic, flat frequency characteristic curve; large output signal level and low distortion; no directionality, high sensitivity, and good transient response performance. The disadvantage is that the working characteristics are not stable enough, and the sensitivity of the low frequency band decreases with the increase of the use time. When working, the polarization voltage and preamplifier in condenser microphones need DC power supply, which makes it inconvenient to use. Now the +12V or +48V phantom power is basically equipped on the mixer to supply condenser microphones. Some condenser microphones can be used at times, although the battery can be installed in the microphone, but they are bulky and heavy, which makes it inconvenient to use.
A dynamic microphone is a microphone that is widely used in work. When the microphone picks up sound, the thin diaphragm moves, and the diaphragm drives the coil to vibrate. The coil in the magnetic field converts it into an electronic signal, which is then sent to the tuning Taiwan processing (as shown in Figure 2). Its advantages: good frequency characteristics, flat frequency characteristic curve in the frequency range of 50Hz to 15000Hz; good directivity and low noise; no need for DC power supply, easy to use, and reasonable price.
4. Wireless microphone
The wireless microphone uses wireless channels to transmit sound signals, and its system is divided into a transmitting part and a receiving part (as shown in Figure 3).
There are three types of microphones: condenser microphones, dynamic microphones, and ribbon microphones (rarely).
Uses include: recording microphones, instrument microphones, interview microphones, conference microphones, voice microphones, test microphones, mobile phone microphones, KTV/performance microphones
Signal transmission: wireless, wired
Pointing characteristics: omnidirectional, cardioid, wide-cardioid, super-cardioid, gun-shaped, figure-8, stereo
The transmitting part is usually a hand-held microphone with a built-in transmitter and a built-in battery; a lavalier microphone, a headset microphone or a microphone for musical instruments, and a portable transmitter with a built-in battery, which can be clipped on the belt. The receiving part has a receiving host with the same frequency as the transmitting system, an antenna, a preamplifier and a signal line connected to the mixer. The wireless microphone is widely used, and the user is not restricted by the microphone line and does not affect the audience's visual effect .
The frequencies used by wireless microphones are divided into two types: high frequency (VHF) and high frequency (UHF): high frequency range: 88MHz～108MHz, high frequency range: 450MHz-530 MHz.