Digital Audio - Part 1 Introduction to Digital Audio

Today digital audio tends to be used more than analogue audio as a method of storage. Records and cassette tapes continue to be used, but by a relatively small market. (Compare the prevalence of records 20 years ago to today.) Why is digital audio more prevalent? While there is some debate as to whether or not digital audio actually sounds better than analogue audio, digital audio is certainly easier to reproduce and to manipulate without loss of quality. Because of digital audio, it is much easier for both amateur and professional musicians today to produce studio-quality music.

Digital audio techniques has become relevant in the latest decades due to it's fundamental importance in the development of new technologies for audio generation, processing, storage and analysis. This has been possible thanks to the huge advances in microelectronics and it's application in the production of powerful and complex devices that are capable of handling and transforming sound with an increasing precision and speed the enormous amount of information contained in sounds.

One of the first consequences of the application of digital technology to audio was the development of very dependable audio storage systems that are unalterable and faithful. Another was the great boost to the development of electronic music instruments of great complexity and versatility. The third consequence was the development and application of techniques for the processing of the audio signal that allowed not only the improvement of processes that before were handled analogically, but also the introduction of new processes, we can find among them  a huge amount of effects such as delays, modulations, reverb, and specializations of amazing realism, whose analogue implementation would be too costly and destined to a much more restricted market.

The basic idea behind digital audio is to represent sound using numbers ("digital" comes from digit meaning number).  Before we start with the analysis we can see how this provides several advantages. In first place the problem of information alterability is eliminated. It is much easier to store a number than the physical magnitude that this number represents. For example if we wanted to store a 22.53 in dipstick we would be in serious trouble. The dilatation cause by temperature or any dust particle that sticks to it's extremes of simply wear from use could cause an error. This is valid for the length of a dipstick, it is even more valid for the magnetic field store in a recorded cassette.

In second place, there are algorithms (calculation methods) to achieve digitally not only the processing types used in traditional audio like amplification, mix, modulation, filtering, compression and expansion, etc. But also others like delays, sync, frequency displacement, sound generation using diverse procedures, etc. These algorithms can be implemented using a general purpose computer or in specific devices called Digital Signal Processors (DSP).

In third place, the replacement of analogue processors for their digital counterparts allows to avoid signal degradation due to analogue noise, something very convenient because analogue noise is hard to eliminate.

Bibliography: Federico Miyara (2003) Acústica y sistemas de sonido. UNR Editora
ISBN 950-673-196-9