Audio processing systems have been a part of many people's lives since the invention of the phonograph in the 1870s. The resulting string of innovations sparked by that disruptive technology have culminated eventually in today's portable audio devices such as Apple's iPod, and the ubiquitous MP3 (or similarly compressed) audio files that populate them. These may be listened to on portable devices, computers, as soundtracks accompanying Blu-ray films and DVDs, and in innumerable other places.

Coincidentally, the 1870s saw a related invention – that of the telephone – which has also grown to play a major role in daily life between then and now, and likewise has sparked a string of innovations down the years. Scottish born and educated Alexander Graham Bell was there at their birth to contribute to the success of both inventions. He probably would be proud to know, were he still alive today, that two entire industry sectors, named telecommunications and infotainment, were spawned by the two inventions of phonograph and telephone.

However, after 130 years, something even more unexpected has occurred: the descendents of the phonograph and the descendents of the telephone have converged into a single product called a ‘smartphone’. Dr Bell probably would not recognise the third convergence that made all of this possible, that of the digital computer – which is precisely what today's smartphone really is. At heart it is simply a very small, portable and capable computer with microphone, loudspeaker, display and wireless connectivity.

Computers and audio

The flexibility of computers means that once sound has been sampled into a digital form, it can be used, processed and reproduced in an infinite variety of ways without further degradation. It is not only computers (big or small) that rely on digital audio, so do CD players, MP3 players (including iPods), digital audio broadcast (DAB) radios, most wireless portable speakers, television and film cameras, and even modern mixing desks for ‘live’ events (and co-incidentally all of these devices contain tiny embedded computers too). Digital music and sound effects are all around us and impact our leisure activities (e.g. games, television, videos), our education (e.g. recorded lectures, broadcasts, podcasts) and our work in innumerable ways to influence, motivate and educate us.