How Digital Audio Works
Why do we need digital audio, when analog audio so accurately represents the original sound? We need digital audio because analog audio has several limitations. First, since analog audio uses a continuously fluctuating voltage level to represent sound, any variation in that level such as a bit of electrical interference, will be heard when the signal is passed through another transducer such as a loudspeaker and becomes sound again. Second, you can’t process analog audio in your computer without first converting those signals into numbers.
A digital audio system uses numbers to store, process, and transmit data. Digital equipment uses an analog-to-digital converter (A/D converter) to convert analog signals into digital form. The converter uses a process called sampling to create discrete numerical values. The A/D converter measures the voltage level at regular time levels. In the second illustration in the screen shot below the numbers on the x-axis represent a certain number of snapshots per second. The y-axis represents signal strength, or the numerical values of those snapshots. The third illustration shows how the digital converter rounds off the continuous levels of the analog signal to the numerical values, resulting in the digital signal shown in the fourth illustration.
After the A/D converter converts the sound into digital form you can process it or store it on your computer. If you want to play the sound back through your speakers or headphones, it must be converted back into analog form. We use a digital-to-audio converter, or DAC, to perform this task.
Some common digital devices include:
- Computer audio interfaces
- Digital effects, such as guitar-amp simulators
- Portable digital recorders
- Digital instruments, such as MIDI synthesizers
- Digital connections