Digital Audio Fundamentals

Information about digital audio production, processing and editing, as well as resources available at the Library.

Introduction to digital audio

The vast majority of recorded sound captured over the last 20 years is digital.

Sound recording developed through various advances since the end of the 19th century via analogue methods of capturing sound - from wax cylinders to long-playing vinyl records to magnetic cassette tape. By the 1970s, technological developments had led to the ability to capture audio in digital formats. This was integral to the development of compact discs in the early 1980s, and subsequent developments have resulted in online digital streaming being the most popular way of consuming music, podcasts and audiobooks in the 21st century.

Digital audio essentially is sound converted into a digital form. An audio signal's analogue soundwave is encoded as numerical samples in continuous sequence. Sound recording using digital technology is based on this interchange between analogue (e.g. the human voice) and digital (e.g. binary code). It is the predominant form of recording used in audio engineering, record production, and broadcasting and telecommunications today. Digital formats allow for efficient use of audio signals, including storage, transmission and retrieval.

Analogue formats are subject to gradual degradation of the original audio signal through making copies (known as generation loss), as well as the practicalities of storing analogue formats like magnetic tape. Digital audio has none of these drawbacks - so long as the digital coding remains intact, infinite copies can be made without any loss of signal quality.

Digital audio files and formats

The process for recording live audio in a digital format is largely the same process as analogue recording. The audio is captured by a transducer such as a microphone, changing the analogue signal into an electric signal. This signal is then converted into a digital signal via the medium for recording.

Digital audio signals can be stored on CDs, digital audio players, hard drives, USB drives, or any digital data storage devices.

Once stored, digital audio signals can be processed and manipulated - for sound production, digital audio workstations (DAWs) such as Protools, Ableton or Logic Pro are often used.

Since raw digital audio files (WAV files) can be very large, audio data compression techniques, such as MP3, Advanced Audio Coding (AAC), Ogg Vorbis, or lossless formats such as FLAC, are often used to make file sizes more manageable for storing or transmission.

Sample rate & bit depth

 Some of the key factors in the quality or resolution of a digital audio recording is the sample rate, and bit depth.

When analogue waveforms are converted to digital signals, they are essentially described as a continuous series of discrete amplitude (i.e. the maximum displacement from equilibrium) values.

This is achieved via capturing a quick series of short samples of a specific size (i.e. bit depth) at a fixed rate. Each sample contains the necessary data, such as dynamic range and frequency content, to reproduce the original waveform.

The amplitude in each sample is quantised, which means it is mapped to a set of discrete finite values. By reproducing these values in the same order and rate that they were captured, in theory an identical copy of the analogue waveform is created.

To use compact discs as an example, every second of music on a CD is made up of 44,100 samples (44.1 per second = the frequency in kiloHertz (kHz)) at a sample depth of 16-bits (the resolution, or quality of the signal). The CD player converts the digital information on the disc into an audio signal for playback.

Here's a video that explains this clearly:


Lossy vs Lossless Compression Differences and When to Use.

Mornington-West, A. (1996). Digital theory. In Borwick, J. (Ed.). Sound recording practice (4th ed.) (pp 37-84). Oxford University Press.

Thompson, D. M. (2005). Understanding audio. Berklee Press.

From the Pictures collection

Man sitting in radio broadcast studio adjusting levels, with turntables and microphone in foereground

Radio announcer seated at desk with turntables, studio equipment and microphone for 2QN, Deniliquin; H2009.88/4 

Lossy vs lossless files

Lossless and lossy file compression describes whether all original data can be recovered when a particular digital file is uncompressed. While used in digital audio production, this principle is also applicable to digital formats used in photography, design and video.

With lossless compression, every bit of data originally in a file remains after it is uncompressed, and all the information is restored. 

Lossy compression reduces file size by permanently eliminating certain information, especially redundant information. When the file is played back, some original information is not there, although the user may not notice it.

The differences between lossy and lossless compression

  Lossy Lossless
What it does Permanently removes file data Restores and rebuilds compressed data
When it's used When file information loss is acceptable When file information loss is unacceptable

Images, video, audio

Text, images, audio

File types

Images: JPEG


Audio: MP3, AAC

Images: RAW, BMP, PNG

General: ZIP

Audio: WAV, FLAC

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