Fundamentals of data representation: Analogue and digital

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PAPER 2 - ⇑ Fundamentals of data representation ⇑

← Sounds Analogue and digital Sampled sound →

For a computer to store sound files we need to get the continuous analogue sound waves into discrete binary values:

An analogue sound wave is picked up by a microphone and sent to an Analogue to Digital (ADC) converter in the form of analogue electrical signals. The ADC converts the electrical signals into digital values which can be stored on a computer.

Once in a digital format you can edit sounds with programs such as audacity.

To play digital audio you convert the sound from digital values into analogue electrical signals using the DAC, these signals are then passed to a speaker that vibrating the speaker cone, moving the air to create sound waves and analogue noise.
Analogue to Digital Converter (ADC) - Converts analogue sound into digital signals that can be stored on a computer
Digital to Analogue Converter (DAC) - Converts digital signals stored on a computer into analogue sound that can be played through devices such as speakers
fig 1. The original analogue sound wave is a continuous set of points
fig 2. ADC converts sound into digital data
fig 3. DAC converts digital data into analogue sound, the analogue wave produced may differ significantly from the original sound wave
Exercise: Analogue and digital
What is the difference between analogue and digital data?


Analogue data is continuous, allowing for an infinite number of possible values. Digital data is discrete, allowing for a finite set of values
Name the device used by computers to convert sound files into sound coming out of the speaker


Digital to Analogue converter
Name a peripheral that could be used to feed sound into a ADC


A microphone

This is a diagram of a system set up for recording, storing and saving sound. Fill in the numbers from the following options

  • ADC
  • DAC
  • Headphones
  • Main Memory
  • Microphone
  • Secondary Storage


  1. Microphone
  2. ADC
  3. DAC
  4. Main Memory
  5. Headphones
  6. Secondary Storage

Why is it difficult to save analogue sound waves in a digital format?


Analogue is continuous data, converting continuous data to discrete values may lose some of the accuracy