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Are you also one of those who thought that Microphones are only used to amplify sounds? No Microphones are electronic devises that capture produced sounds correctly for storage or future use. One of its purposes is to capture sounds, convert them into electrical energy and connect them to a Speaker which has high volume capabilities for an amplified sound. In Audio and Video Productions, Mics are a very important accessory. In all productions you want to capture correct sounds in dubbing or Live. This is where you choose a Mic according to your needs, so that you can capture sounds in the best possible way. Microphones are basically acoustic to electric transducers, machines which convert audio signals to electrical energy and back |
The most common microphones nowadays use a thin membrane which vibrates in response to sound pressure. This movement is subsequently translated into an electrical signal. Most microphones in use today for audio use electromagnetic induction (dynamic microphones), capacitance change (condenser microphones) or piezoelectric generation to produce the signal from mechanical vibration
Dynamic Microphone:
| The dynamic microphone consist of movable metallic disc (diaphragm) attached to coil of wire suspended within a magnetic field. When sound waves strike the diaphragm, it moves in response to the variations in pressure. This in turn causes the coil to move within the magnetic field, creating a patterned electrical current.The advantage of the dynamic microphone are it s physical ruggedness and its ability to operate without external power and withstand loud sounds. On the negative sound, most microphones do not respond to rapid changes called transients. |
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Condenser Microphone:
| Condenser microphone's transducer consists of two very thin electrically charged metallic plates, one of which is fixed in place. The other vibrates in response to sound entering the microphone. The movement of these plates creates patterns of electric currents corresponding to the sound the microphone picks up. Condenser microphones are rugged, small and capable of responding rapidly to transients. Their small size and excellent response characteristics make them popular for television production but they do have some disadvantages. Condenser microphones have difficulty reproducing loud sounds without distortion. A condenser microphone may die in middle of the production. | {border-color:white}.  |
Piezo
Electric or Crystal Mics:
These microphones are
made of either of the following:
Tourmaline, Quartz, Rocher's Salt.
When the diaphragm's made of these elements are pressurized they
create electrical energy. Cheap in cost, used in built in recorders
or other contact mics in ECG Machines,
Stethoscope, USG Machines. Though they
have a lot of system noise, they have relatively longer shelf
life.
Polar Pattern
of Microphones:
Polar Pattern of a Mic is the directional response to sound. It is the angle of picking up sounds that a mic follows at all times. It is also the sensitivity of the mic on the basis of the direction the sound is coming from.Microphones differ dramatically in their sensitivity to sound coming from different directions. On the basis of Polar Patters there are 4 major types of Microphones:
Omnidirectional
microphones:
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| Merits | Demerits |
| Picks up sounds from all directions | Records Ambient Sounds as well |
Bi-directional microphone:
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| Merits | Demerits |
| Proximity Effect | Highly Sensitive, cannot be used in rough conditions |
Cardiod microphones:
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Cardiod microphones are also called unidirectional microphones
because they tend to pick up sound coming form one general
direction. Within the cardiod family there are other microphones with the following angle of pick up: Cardiod- 170 degree angle of pick up of sound Super Cardiod: 100 degree angle of pick up Hyper Cardiod- 60 degree angle of pick up. |
Poly Directional Microphones:
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These have the facility to flick from omni to bi to uni directional
microphones Accessories of a Microphone
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How to select
a Microphone?:
- Polar Pattern. Eg, Unidirectional Mics are best in places with high ambient sounds.
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Frequency Response to sounds. Eg, If your speaker talks slowly you will need a microphone with High Frequency Response which converts low frequencies to higher ones. When the orginal source is at extreme low volume.
- Sensitivity to sound
- Robustness towards external conditions like dust, etc
- Sensitivity to physical handling.
Glossary:
Diagrams of Omni Directional, Bi Directional, and Uni Directional Microphones represent the angular pick up of each of the mics.
