microphones

Microphone Essential

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Basics

What is a microphone?

A microphone is a transducer that converts acoustic energy to electrical energy. It has many uses in today's world from medicine to musical recording.It reacts to a pressure input by use of a diaphragm.

History

The Invention of the Microphone

1876 – Alexander Graham Bell 1878 – Hughes (First use of term ‘microphone’)

(actually, a carbon microphone )

- Used for telephony- Use pressure which get converted to resistance- And done well since then

1920’sThe Rise of Broadcasting

Microphones used for telephony had limited dynamic range and high distortion.

Commercial broadcasting required better microphones.

MicrophoneTypes

Dynamic Microphones

1. Dynamic moving coil microphones employ a coil of wires attached to a diaphragm, which is suspended within a magnetic field.

2. Acoustical vibrations cause the diaphragm and the coil to vibrate within this magnetic field, creating an AC (alternating current.)

3. This current electrically represents the audio signal.

Condenser Microphones

1. Condenser microphones use two adjacent plates. One is stationary, while the other, a diaphragm, vibrates to incoming acoustic signal.

2. These two plates are charged with a constant voltage - phantom power. As the distance between the stationary plate and diaphragm varies with incoming vibrations, a varying electrical current is generated.

Ribbon Microphones1. Again principle of induction is used2. Ribbon (Induction) is used as diaphragm3. Oscillates between magnetic poles4. Bi-directional

LavalierLavalier microphones are small, lightweight microphones designed to be attached under the chin of the speaker. Attached to the talker’s clothing in such a manner that they will not move and produce rustling noises.Common in television and film production because they are easy to conceal.

PhantomPower

Phantom power is a method of powering a condenser microphone using another device. For example, the cable from the microphone to the audio mixer or videotape recorder could carry power as well as audio signals. If you are able to provide a microphone phantom power, you will not need batteries!

Dynamic V/s Condenser

Microphones

Dynamic Microphones

Actual energy to energy transfer 1:1

Accurate representationLow costLess sensitive (smaller sound field)More durable than other types of microphones

Condenser Microphones

Amplified transfer of energy is more than 1Extremely accurateHigher costVery sensitive (larger sound field)Less durable (prone to humidity and shock)

Polar Pick-up PatternMicrophones

A polar pick up pattern is a graph used to show the microphone’s sensitivity to sound coming from different directions.Example

Microphones : Types of Polar Pattern

Omni directionalBi-directionalCardioidSuper CardioidHyper Cardioid

How to ChooseMicrophones

Decibel (dB) scaleMeasures how sensitive the microphone is

Frequency Response“Bandwidth“ of microphone

On-axis responseResponse to sound coming directly to the microphone

Off-axis responsesResponse to sound coming from all angles

Diffuse field responseResponse to sound coming from reflections

Equivalent noise levelNoise from microphone itself (good if <15db)

SensitivityWhat voltage a microphone will produce at a certain sound pressure level

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