Micro phone is a very common device that you see almost daily in your life. It is a very common equipment hat one can see in stage programs, television shows, churches, meetings etc, or may even use it. We see it we use it but most of us never think “How does it work!!”.
What is a microphone?
Microphones convert a sound wave into an electrical signal. The converted electrical signal will have the voltage and current are proportional to the original sound. It works on the principle of electromagnetic induction. According to this principle, “EMF is induced in a magnet- coil assembly when ever there is a relative motion between them”.
Parts of a microphone
The sound waves from the speaker strike diaphragm of the microphone, which causes the core to move within an electro-magnetic field, which, in turn, induces EMF in the core. This signal is then amplified, filtered to reproduce the original sound wave and reinforce it. The working principle varies from one microphone to other based on the type. However this is the very basic principle behind them.
Typical output devices for microphones are power amplifiers, sound mixers, PA systems and audio recorders
Classification of microphones
Classification of Microphones
Microphones can be classified based internal configuration as follows:
- Dynamic Microphones
- Ribbon Microphones
- Condenser Microphones
Microphones can be classified based external configuration as follows:
- Wired Microphones
- Wireless Microphones
In dynamic microphones a physical cone acts like a lens to concentrate the incoming sound waves. The sound waves falling on the diaphragm moves the cone and its attached coil into a magnetic field. The magnetic field induces EMF in the coil present over the core which is the microphone's output. The voltage and current produced on the coil will be proportional to the original sound. This is then amplified and filtered to reproduce the original sound. Dynamic microphones are well known for their versatility and their durability.
Ribbon microphones are relatively simpler than the other two types. It consists of a thin strip of metallic foil which is between two magnetic plates. When sound waves fall over the foil, it vibrates which in turn produces fluctuations in the electrical current in the foil. These variations in current is sensed and reproduced into audio signal.
Ribbon microphones are extremely sensitive configuration that can be used for wide range of frequencies and produces an extraordinarily rich representation of the original sound. The sound reproduction capability of ribbon microphones are better than dynamic microphones and Condenser microphones.
These ribbon microphones are very sensitive to physical impacts. Hence they are not considered portable and can be easily damaged by power overdrive.
Condenser microphones works on the principle of capacitive effect.
The condenser microphones have a thin diaphragm and solid back plate. The thin diaphragm and solid back plate acts as two plates of a capacitor. As the diaphragm vibrates, the distance between thin diaphragm and solid back plate varies, which causes change in capacitance. This variation in capacitance corresponds to the sound waves of the speaker.
Condenser microphones are used for a variety of applications.
Classification based on external configuration of microphones
Michael Jackson with wireless hand held microphone
Jackson with wireless hand free microphone
Wired Microphones are connected to the external amplification and mixer circuit through wire. The electrical signal produced in the microphone to taken to the external circuit through a wire. This type of microphone limits the freedom of movement. It is less costly than the wireless microphone.
Wireless Microphones do not have wires which gives microphones is freedom of movement. The wireless transmitter is either built into the microphone or is connected by a short cable to a body pack transmitter. It transfers the sound signal to the external circuit as an RF signal through a wireless transmitter. The external devices have the RF receivers. The received signals are demodulated and then amplified. All wireless transmitters require a battery. It can be used within a specified range from its receiver.
The main advantage of wireless microphones as compared to wired microphones is it gives more freedom of movement.
The disadvantage is its price as wireless microphones are more expensive than the wired microphones.
Types of wireless microphones
- Handheld Wireless Microphones
- Hand free Wireless Microphones
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Ethan Webber from London, UK on November 19, 2013: