Sound cards are a key component to any computer system. They let you listen to music while using your computer and they also bring games to a new level! They add all sorts of sound effects to your computing experience.
Sound cards perform four basic functions with sound. They can play music or other sounds (i.e. from MP3s, from CDs, games, etc), they can record sounds (by the use of a microphone or other similar device), they can synthesize sounds, and finally, they can process sounds.
You might be wondering how sound cards can take sounds like your own voice and save them as files to your computer's hard disk. Well, first, you will need some sort of device, like a microphone. When you speak into the microphone, a device inside the microphone will convert your voice to electrical signals that your sound card can understand. Your voice is in analog form, and not digital. This merely means that it is not in the form of the binary digits (bits) of 1 and 0. In order for the sounds to be saved and used later by the computer, the sound card must convert the analog signals into digital signals. This is done by a special device called the analog-to-digital converter (ADC).
The digital output created by the ADC then enters the digital signal processor, or DSP. Because sound files are usually really really big, they need to be compressed so that they won't take up too much room in your hard disk. This, along with many other different computations, is done by the DSP.
Finally, the output created by the DSP is transferred to the computer's central processing unit. It is sent to your hard disk, and is usually saved as a .wav file.
Playing sounds saved as a .wav file in your hard disk is a fairly straightforward task. The computer's CPU retrieves the file from the hard disk and ships it off to the sound card. The file is decompressed by the DSP, and is then converted back to analog form by the digital-to-analog converter (DAC), and the music is ready for us to listen to!
Musical Instrument Digital Interface (MIDI):
Almost all sound cards have a MIDI synthesizer
or sampler. MIDIs let MIDI computers communicate with MIDI instruments. At
first, MIDI sound cards made use of FM synthesis. FM synthesize can produce
sounds by taking two or more sound waves and them combining them to make an
approximation of a particular sound. It can be pretty realistic, but now there
is a newer technology called wavetable synthesis. Wavetable is much more realistic
than FM synthesis because it creates sounds by taking samples of real instruments.
For example, if it wanted an example of an A flat on a piano, it would take
a sample of a piano playing A flat. The sample sound is played in a loop and
can realistically recreate the sound of the original instrument!
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