• Operating Principle -- What physical principle is used to convert mechanical energy into electrical energy?

• Directional Characteristic -- How does the microphone respond to sound arriving from different directions?

Carbon Microphone:

Operating Principle:

• The movement of the diaphragm compresses carbon granules, varying the electrical current.

Advantages:

• Cheap to manufacture
• Rugged

Disadvantages:

• Requires external power source
• Limited frequency range
• Limited sensitivity

Piezo Microphone:

Operating Principle:

• The movement of the diaphragm bends a crystaline materiel, varying the electrical current generated. (Same principle as a BBQ starter wand.)

Advantages:

• Cheap to manufacture

Disadvantages:

• Fragile
• High electrical impedance limits cable length

Dynamic Microphone:

Operating Principle:

• The movement of the diaphragm causes a small coil of wire to move in a magnetic field, varying the electrical current generated. (Same principle as bicycle dynamo.)

Advantages:

• Good quality for reasonable price

Disadvantages:

• Susceptible to external magnetic fields (hum)
• Magnet is heavy
• Magnetic shielding is heavy
• Inertia of coil limits sensitivity

Condensor Microphone:

Operating Principle:

• The movement of the charged diaphragm causes a change in electrical capacitance, varying the electrical current generated.

Advantages:

• Thin diaphragm is light
• -- good sensitivity
• -- good high frequency response
• Can be made small

Disadvantages:

• Requires external voltage source
• Expensive to manufacture

Ribbon Microphone:

Operating Principle:

• The movement of the ribbon within a magnetic field, varies the electrical current generated.

Advantages:

• Good high frequency response

Disadvantages:

• Fragile to mechanical shock, wind, voice pops
• Very low electrical impedance requires transformer

Unidirectional Dynamic:

Unidirectional Condensor:

Undidirectional Ribbon:

Omnidirectional Polar Response:

Cardioid Polar Response:

Polar Responses Compared:

Distance Factor:

Microphones with higher directivity can work farther from source.

Proximity Effect:

All directional microphones exhibit a boost in bass (low frequency ) response when working close.

Boundary Effect: