Unit 17 Audio production: LO3

History of microphones

A microphone is a device that converts sound waves to electrical current, the device is usually plugged into an amplifier, recorder, or broadcast transmitter. In 1827 Sir Charles Wheatstone was the first to use the term microphone, and in 1876 Emile Berliner was the first to invent the voice transmitter or microphone in the telephone that improved the telephone device. Within 2 years David Edward Hughes, invented the carbon microphone which was later developed in the 1920’s. In the year 1964 James west and Gerhard Sessler received patent number 3, 118, 022 for their electric microphone, this microphone had something different to the other microphones as it had a greater reliability with a lower price, this allowed the general public to obtain the item themselves. Around 1 billion electric microphones were manufactured each year. In the 1970’s dynamic and condenser microphones were developed as they became perfect to broadcast with as they had lower sound level sensitivity and clearer sound recording, they are now used to broadcast worldwide.

How it works

A microphone is used to turn sound energy into electrical energy, this is done because, as someone speaks into the microphone the energy is carried by vibrations into the air, the diaphragm and coil move back and forth as the sound waves hit them, the magnetic field cuts through the coil as the coil moves back and forth through the magnetic field and allows an electrical current to pass through, and this creates the electrical energy that is moved through the microphone.

Microphone types

· Dynamic

These types of microphones are for general use, it is a very simple creation and is easy to use with little moving parts, they are suited to record high volume levels, for example the recording of musical instruments and amplifiers. The dynamic microphone uses the magnetic current from the wire coil to create the audio signal. The dynamic microphone is basically a loudspeaker in reverse; dynamic microphones usually don’t have a flat frequency response unlike condensers. The downsides of the dynamic microphones are the poor frequency response, and low output level. This is a commonly used microphone as it is cheap robust and can be used in most situations

· Capacitor

A capacitor microphone can also be called a condenser microphone, these types of microphones are expensive and require a power supply, and they give a high quality sound signal and are used in laboratories and studios during recording. This type of microphone stores energy in an electrostatic field. The capacitor microphone is audio sensitive compared to other microphones such as the dynamic microphone. This microphone consists of a couple of plates with voltage running between them; one has a lighter material and acts as the diaphragm. When sound waves appear the distance between the plate’s changes as does the capacitance.

· Ribbon

The ribbon microphone is also known as the velocity microphone and was one of the last types of microphones to be developed, the natural sound of this microphone is warm big and soft. When using a ribbon microphone it is important to use a breath filter as the microphone is delicate, it is dangerous to blow into a ribbon microphone as it can seriously damage the product. Today only a few manufactures offer ribbon microphones therefore they are harder to find and are more expensive than a dynamic microphone.

· Carbon

The carbon microphone was first used within telephones and was popular into the 1970’s, this type of microphone contains loosely packed carbon grains this helps the diaphragm vibrate by making the grains compress and release making the resistance of the microphone change. These types of microphones where known for their high output level, low impedance and low cost however it had low quality sound reproduction and limited frequency response. The advantages of this microphone were that it could boost weak signals.

· Crystal

The crystal microphone changes their electronic properties when they make a different shape, if you attached the crystal to the diaphragm it will create an electrical signal when the diaphragm vibrates. This microphone is used for studio, home recording and live recording.

· Tie clip /lavier

This type of microphone is used to be clipped onto a person’s shirt, to record the person’s voice. These types of microphones are Omni-directional which means the direction of which the microphone is pointing is not significant; it can also pick other sounds around the area of recording. These types of microphones are used in stage plays, film sets and television programmes.

· Radio microphones

These microphones are more in demand and allow the users to move around more easily without picking up all surround sound, this microphone is known for its mobility and very valuable in the media field. This microphone is wireless and is very good for short distance communication.

Polar patterns

The image below shows the different patterns for microphones.

Application

What is a microphone used for?

If you are a musician or work in TV or radio a microphone is a very useful thing to obtain, it has many different uses it allows voices to be heard louder and clearer and to a larger area of people. A microphone is an electromagnetic device that uses vibration to create a signal. As well as that use they are also used to detect volcanoes and earthquakes.

Microphone bibliography

http://www.mediacollege.com/audio/microphones/how-microphones-work.html

http://inventors.about.com/od/mstartinventions/a/microphone.htm

http://www.explainthatstuff.com/microphones.html

http://www.mediacollege.com/audio/microphones/dynamic.html

http://www.coutant.org/ribbons.html

http://www.bing.com/images/search?q=what+is+a+carbon+microphone&view=detail&id=706F07C7EAE357F4D5502328AA7B6B255618F4A5&first=0&FORM=IDFRIR

http://www.bing.com/images/search?q=what+is+a+radio+microphone&view=detail&id=D2B129BFD9699AE626A88764763EAE7EDCAF1E15&first=0&FORM=IDFRIR

http://en.wikipedia.org/wiki/Microphones

Most of you will have used a dynamic mic at sometime or another -- if it looks like a mesh ball on a stick, then it's almost certainly a dynamic model. In live sound, nearly all the mics used are dynamics, and in the studio, instruments such as drums, electric guitars, and basses may also be recorded using dynamic mics. Dynamic microphones have the advantages of being relatively inexpensive and hard-wearing, and they don't need a power supply or batteries to make them operate. So, how do they work?

Capacitor mics have been around for several decades, and although modern capacitor mics do incorporate a few small technical improvements, the sound character has actually changed very little -- some of the best-sounding models were designed over 20 years ago. Basically, the heart of any capacitor mic is a pair of conducting plates, one fixed and the other in the form of a moving diaphragm. When the spacing between the plates changes (as it does when the diaphragm vibrates) the capacitance varies, and if a fixed electrical charge is applied to the capacitor, an electrical signal is produced which faithfully represents the diaphragm vibration.

There is another type of capacitor microphone, known as the electret mic. Despite inauspicious beginnings, these have now been developed to the point where they can rival true capacitor quality for a much lower price. Instead of applying an electrical charge to the microphone capsule via an external power source, electret mics use a diaphragm made from an insulating material that has a permanent electrical charge. A preamplifier is still needed, but this can be built very cheaply, and will run from a battery in some cases.