Sound sampling & sorting

• Microphone


  Converts the sound pressure wave into an analogue electrical signal with a voltage amplitude that varies in accordance with the pressure amplitude of the original signal
• In the past, sound signals were mixed, stored and processed using only analogue methods
• Nowadays all these processes are almost always done using digital techniques
• Advantages of working with sound in its digital form

  • Immunity from signal corruption through extensive processing or through transmission or storage
  • Mixing and processing of sound comes down to a simple process of computation ('number crunching'), rather than involving complicated analogue electronic circuits and devices
  • Computer storage techniques can easily be used for storing sound in its digital form
• Digital sound


  Working with sound in its digital form, often referred to as working in the digital domain, basically means working with numbers
• Analogue-to-digital conversion


  1. Sampling

  2. Quantisation
• Sampling


  Measuring the amplitude of the sound wave at regular time intervals
• Sampling rate


  The number of times per second we take a sample
• The plateaux at every sampling point represent the intervals between samples, where we have no information, and so assume that nothing happens
• This means that the audio signal produced by the sample does not closely follow the original signal, leading to poor-quality sound
• Improving sampling


  1. Decrease the sampling interval

  2. Take a reading of the amplitude every 0.1 seconds
• Quantisation


  Dividing the maximum voltage range of the analogue sound signal into a number of discrete voltage bands, and each band is represented by a number
• The faithfulness of the digital copy to the analogue original will depend on how large a range of numbers we make available