Microphones

Microphones
by Keegan

When people wish to communicate to a large crowd or when they want to record sound, a microphone is a valuable piece of equipment. The microphone (sometimes called a "mike") was first invented by Emile Berliner in 1877. However, Alexander Graham Bell was the first person to develop it and make it useful. Today, microphones are used in telephones, hearing aids, radios, tape recorders, and television broadcasting.

What is a microphone?

A device for turning acoustic power into electric power is called a microphone. Acoustic power is real sound waves. In other words, it changes sound into an electric signal. These signals are usually sent to an amplifier or recording device. There are many different brands and also different types. Still, they all have one thing in common: they all use a diaphragm.

This diaphragm is a thin part, sometimes made of metal, that vibrates when sound goes to the microphone. When the diaphragm shakes, it causes the other parts of the microphone to create signals.

What are the different types of microphones and where are they used?

Let’s start with dynamic. The dynamic microphone has a thin diaphragm that is hung by suspension wires. It can break if the wires become damaged. One bad thing about this kind is that because it is less sensitive, it does not pick up sounds as well. But it is great for live performances and recordings that want to sound like live performances.

Carbon is the next kind of microphone. It is an old fashioned design, used on the first telephones. It uses carbon dust which is compressed into the middle of the diaphragm. It makes electrical signals when the sound waves pass through the dust. It is still used on many telephones.

The ribbon is another variety of microphone. Ribbon microphones use a very thin metal wire that is suspended in a magnetic field. When the sound waves or vibrations hit the ribbon, the ribbon vibrates and sends waves through the magnetic field creating electric signals. Ribbon microphones are very sensitive and usually used for special recordings. They are very fragile and can break easily when dropped.

A condenser microphone is the next kind we will learn about. A condenser microphone has a diaphragm separated by carbon that acts as a capacitor. A capacitor is a thing that stores electric energy. So don’t go around touching capacitors. The condenser microphone stores and releases the electronic signals when the diaphragm vibrates. They are very sensitive and are used for voice. If you have a bad voice, don’t use a condenser microphone, because they pickup sounds as they really are.

The last kind of microphone is the crystal microphone. Crystals change their electronic properties when they change shape. So, if you attach a crystal to a diaphragm, a crystal will create an electric signal when the diaphragm is vibrated.

How are microphones powered?

The easiest most understandable power is microphones that use batteries. Other microphones are powered by the device that they are plugged into. Often times when you see a microphone on a stage, it is plugged into an amplifier. The amplifier is plugged into the wall. This power then runs the microphone. The last type of power is called phantom power. This is power that runs from a cable hooked up to a power pack just for the microphone. Phantom power is for condenser microphones.

What are pickup patterns?

A pickup pattern is the way a microphone picks up a signal. It is based on what direction the sound is getting to the microphone.

The first one is omnidirectional. This kind of microphone picks up sound from all directions. These are used for group vocals and recordings.

Unidirectional microphones pickup sound from only one direction. They are good for recording single voices. This makes them good for interviews in places that are loud. Because they can pickup from long distances, they are also great for surveillance.

Next is bi-directional. It gets sound from two places. It is great for recording two voices at the same time.

Carotid is the last type of pickup pattern. It is very unusual, because it picks up sound in a heart shaped pattern. These are actually a very commonly used microphone. They are great for talk shows, because the audience sound will not be picked up as much as the people on stage. This also makes it very good for live music performances.

Those are the main types of microphones. There are also several others that are not as common as the main types. They are called specialty microphones.

What kinds of specialty microphones are available?

Wireless microphones are one kind of specialty microphone. They contain an internal transmitter that sends signals over radio waves to a receiver. Lavalier microphones are another kind. They are usually wireless, and they are small microphones that can be clipped on a shirt. Bass microphones have a very large diaphragm that makes a very loud signal. They are usually used inside drums are rock concerts. Finally, pressure zone microphones are a general purpose microphone that amplify large sound sources like choirs or other large groups.

Microphone Trivia Questions

1. What do all microphones have in common?
a. They all pickup sound the same direction
b. They all use a part called a diaphragm
c. They all use carbon dust
d. They are all used for drums

2. What does the carotid pickup pattern look like?
a. A circle
b. A diamond
c. Nothing
d. A heart

3.  Which kind of microphone has everything held up inside with thin wires?
a. Carbon
b.  Phantom power
c.   Crystal
d.   Dynamic

Citations

Online Resources

"History of Microphones." About.com. 12 January 2005
<http://inventors.about.com/library/inventors/blmicrophones.htm>.

"How do Microphones work and why are there so many different types?" How Stuff Works. 14 January 2005 <http://electronics.howstuffworks.com/question309.htm>.

"Microphones." Multimedia bluffers guides. 14 January 2005
<http://home1.pacific.net.sg/~firehzrd/audio/mics.html>.

Images

Photographs of Alexander Graham Bell and a microphone with cord have been released into the public domain under the terms of the GNU Free Documentation License from Wikipedia, the Free Encyclopedia. <http://en.wikipedia.org/wiki/Main_Page>.

Copyrighted clip art images of man with microphone animation, crystals and radio tower from "Microsoft Office Online" <http://office.microsoft.com/clipart/default.aspx?lc=en-us&cag=1> (October-March, 2004-2005). Clip art available only to licensed users for non-commercial purposes.