TheBigBlack's Guide To Digital Audio

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Basics

Before you can understand the differences between analog and digital you must first have a basic understanding of how each works.

Some of the terms used below may be gibberish to you at this point, but all are explained in greater detail later in the texts, should you want further information.

  1. What Is Analog Audio?
  2. What Is Digital Audio?
  3. What Are The Advantages Of Digital Audio?

What Is Analog Audio?

All sounds we hear with our ears are made of pressure waves in the air. Starting with Thomas Edison's demonstration of the first phonograph in 1877, it has been possible to capture these pressure waves onto a physical storage medium, and then reproduce them later by mimicking the same pressure waves.

Audio pressure waves, or waveforms, look something like this:

Waveform

An analog audio system (for example, a tape recorder) captures sounds, and converts their physical waveforms into electrical representations of those waveforms by use of a transducer, such as a microphone. The sounds are then stored or instantly transmitted (for example, a live radio broadcast). The process is reversed for playback - the audio signal is amplified, and then converted back into physical waveforms via a loudspeaker. Analog audio retains its fundamental wave-like characteristics throughout its storage, transformation, duplication, and amplification.

Analog recording media such as phonograph records (vinyl LPs) and cassette tapes represent the shape of the waveform directly, using the depth of the groove for a record or the amount of magnetization for a tape. (This is why putting a cassette on top of a speaker is not a good idea. The magnet in the speaker changes the tape magnetisation, meaning the sound is distorted or even lost all together.)

Analog recording can reproduce an impressive array of sounds, but it also suffers from problems of noise. Notably, each time an analog recording is copied, more noise is introduced, decreasing the fidelity. This noise can be minimized, but never completely eliminated.

What Is Digital Audio?

Digital audio is technology that can be used to record, store, generate, manipulate, and reproduce sound using audio signals encoded in digital form. Digital audio samples the waveform at evenly-spaced timepoints, representing each sample as a precise number.

A digitally sampled audio waveform looks something like this:

Waveform

When recording digitally a microphone converts sound to an analog electrical signal (as per the normal analog process), then an analog-to-digital converter (ADC) converts the analog signal into a digital signal for storage or transmission.

For playback a digital-to-analog converter (DAC) performs the reverse process, converting a digital signal back into an analog signal, which analog circuits amplify and send to a loudspeaker.

Following significant advances in digital audio technology during the 1970s, digital audio rapidly replaced analog audio technology in most areas of sound production, sound engineering, and telecommunications. It has proven extremely useful in the recording, manipulation, mass-production, and distribution of sound. The availability of music as data files, rather than as physical objects, has significantly reduced the costs of distribution. Audio data compression techniques, such as MP3, Advanced Audio Coding, Ogg Vorbis, or FLAC, are commonly employed to reduce the file size. Digital audio can then be streamed to other devices.

What Are The Advantages Of Digital Audio?

No Quality Degradation

One of the biggest advantages of digital over analog is the reduction in possible errors. Analog audio signals are susceptible to noise and distortion, due to the innate characteristics of electronic circuits and associated devices.

Disturbances in a digital system do not result in error unless the disturbance is so large as to result in a symbol being misinterpreted as another symbol, or disturb the sequence of symbols. It is therefore generally possible to have an entirely error-free digital audio system in which no noise or distortion is introduced between conversion to digital format, and conversion back to analog. This is because digital recordings do NOT degrade over time, and can be copied perfectly without introducing any additional noise. Digital audio can even be edited and mixed without noise being added. Therefore, unless done intentionally, the original recording always remains unchanged.

Portability

Digital audio can be stored on any digital data storage device, such as a CD, a DVD, a BD (Blu-Ray disc), a digital audio player, a hard drive, or a USB flash drive.

 

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Last Updated: 25/09/2016