SPEAKER

A speaker is a computer peripheral that reproduces speech and/or music.

Computer speakers, or multimedia speakers, are external speakers and are usually equipped with a male-end phone plug for computer sound cards; however, there are some that have female RCA (phono) plug ports, and some people link computer sound cards to nearby stereo systems. Computer speakers are usually a simplified stereo system without a radio or other media sources built in.

Typically, the simplest computer speakers come with computers. There are advanced forms of computer speakers that have graphic equalization features (bass, treble, etc.) for dynamic audio flexibility.

Sound Basics
To understand how speakers work, you first need to understand how sound works. Inside your ear is a very thin piece of skin called the eardrum. When your eardrum vibrates, your brain interprets the vibrations as sound -- that's how you hear. Rapid changes in air pressure are the most common thing to vibrate your eardrum.
An object produces sound when it vibrates in air (sound can also travel through liquids and solids, but air is the transmission medium when we listen to speakers). When something vibrates, it moves the air particles around it. Those air particles in turn move the air particles around them, carrying the pulse of the vibration through the air as a traveling disturbance.

To see how this works, let's look at a simple vibrating object -- a bell. When you ring a bell, the metal vibrates -- flexes in and out -- rapidly. When it flexes out on one side, it pushes out on the surrounding air particles on that side. These air particles then collide with the particles in front of them, which collide with the particles in front of them and so on. When the bell flexes away, it pulls in on these surrounding air particles, creating a drop in pressure that pulls in on more surrounding air particles, which creates another drop in pressure that pulls in particles that are even farther out and so on. This decreasing of pressure is called rarefaction.

Differentiating Sound
We hear different sounds from different vibrating objects because of variations in:

• Sound-wave frequency - A higher wave frequency simply means that the air pressure fluctuates faster. We hear this as a higher pitch. When there are fewer fluctuations in a period of time, the pitch is lower.
• Air-pressure level - This is the wave's amplitude, which determines how loud the sound is. Sound waves with greater amplitudes move our ear drums more, and we register this sensation as a higher volume.

A microphone works something like our ears. It has a diaphragm that is vibrated by sound waves in an area. The signal from a microphone gets encoded on a tape or CD as an electrical signal. When you play this signal back on your stereo, the amplifier sends it to the speaker, which re-interprets it into physical vibrations. Good speakers are optimized to produce extremely accurate fluctuations in air pressure, just like the ones originally picked up by the microphone. In the next section, we'll see how the speaker accomplishes this.

Driver Types

In the last section, we saw that traditional speakers produce sound by pushing and pulling an electromagnet attached to a flexible cone. Although drivers are all based on the same concept, there is a wide range in driver size and power. The basic driver types are:

• Woofers
• Tweeters
• Midrange