AQA Computer Science GCSE
Data Representation – Representing Sound
Sound also needs to be turned into numbers to turn it into a digital sound file.
This is done by taking a sample on a regular basis across an analogue signal (a sound wave) and recording the amplitude (the volume). This can be expressed as a number – which ultimately becomes a binary value.
The more frequent the sample rate the better quality the audio is – and the large the file. Music files will tend to sample 44,100 times a second, which is a lot of data.
Sound Representation – everything you need to know
Sound Waves – slides from class
Sampling Rate and Resolution – slides from class
Sound File Size – a calculation based on a real 3 minute record
There's an audio file summary that I made for revision purposes as well:
Analogue v Digital
The difference between a digital piano and an acoustic piano (one which creates a purely analogue sound) is that the sound from the acoustic piano resonates much more and the "fills a larger space". It's "bigger" and the bass sound in particular sustains more. It has a "richer" sound with more "depth", particularly depth of pitch (there is a bigger difference between the low notes and the high notes.
Of course, this is dependent on a quality of the piano. A really good quality (and generally more expensive) digital piano will sound much better – and better than a poorly maintained and/or cheap acoustic piano.
The same thing is probably true of hi-fi equipment. A cheap record player might well sound worse than a high quality CD player, despite the CD playing digital audio. Both will probably sound better than the music coming from your phone's speaker...