As sound is analog, we have to digitize it. To do that involves sampling and quantizing.
In the sampling step, the sound wave is sampled at a specific rate into discrete samples of amplitude values. If the sampling rate is higher, the data captured will be more accurate. However, a higher sampling rate will generate a larger amount of data, which will require more storage space and processing time. The sampling rate for CD-quality audio is 44100 Hz, or 44100 samples per second.
In the quantizing step, each of the discrete samples of amplitude values, obtained from the sampling step, will be mapped and rounded to the nearest value on a scale of discrete levels (bit depth). The more levels available in the scale (the higher the bit depth), the higher the accuracy in reproducing the sound—referred to as higher resolution. However, higher resolution will require more storage space.
Sound: Many different types of files
Here are some of the most common ones.
| File Type | Abbreviated From | Compression and Other Information | Created by |
|---|---|---|---|
| .aiff | Audio Interchange File Format | Usually uncompressed, though there is a compressed version | Apple Computer with Electronic Arts |
| .wav | Waveform Audio File Format | Uncompressed and also a number of compressed versions | Microsoft and IBM |
| .mp3 | MPEG-2 Audio Layer 3 | Highly compressed; common audio format for consumer audio storage | Moving Picture Experts Group |
| .aac | Advanced Audio Coding | Highly compressed. Designed to replace .mp3 format, higher quality sound with similar bit rates | Group of companies including AT&T Bell Laboratories, Fraunhofer IIS, Dolby, Sony Corporation and Nokia |
In addition, there are MIDI files. MIDI (Musical Instrument Digital Interface) is a communications protocol that defines a common interface for electronic digital music instruments to communicate with computers, or other instruments or devices containing microprocessors. It specifies the configurations of cables and cable plugs as well as the format of the data. MIDI is a way of describing information and a set of agreed upon standards, not based on an audio waveform.
Now, how do we get sound into our computer? Lots of ways.