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Representing Sound

FoundationHigherAQA

Understand Representing Sound for GCSE Computer Science with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA GCSE Computer Science (8525). Sound is digitised by sampling the analogue wave at regular intervals.

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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA specification. Every worksheet comes with a full mark scheme.

Foundation

WorksheetFoundation · PDFMark SchemeFoundation · PDF

Higher

WorksheetHigher · PDFMark SchemeHigher · PDF

Topic overview

Sound is analogue, varying continuously, but computers store only discrete values. Sampling is how the conversion is made.

The amplitude of the sound wave is measured at regular intervals, and each measurement is stored as a binary value. Sample rate is how many measurements are taken per second, measured in hertz. Sample resolution, or bit depth, is the number of bits used per sample.

Both affect quality and file size. A higher sample rate captures more of the wave's shape, so the recording is closer to the original. A higher bit depth records each measurement more precisely. Both increase the file size proportionally, which is the trade-off every recording decision comes down to.

Revision notes

Sampling

The amplitude of the analogue wave is measured at regular intervals.

Each measurement is stored as a binary value. The recording is a series of these discrete samples approximating the original continuous wave.

Sample rate and resolution

Sample rate: the number of samples taken per second, in hertz.

Sample resolution, or bit depth: the number of bits used to store each sample. A higher bit depth records each amplitude more precisely.

Quality against file size

A higher sample rate captures more of the wave's shape, giving a more accurate recording.

A higher bit depth records each sample more precisely. Both increase file size proportionally, so every recording decision is a trade-off between quality and storage.

Key points

  • Sound is analogue and varies continuously.
  • Sampling measures amplitude at intervals.
  • Each sample is stored as a binary value.
  • Sample rate is samples per second in hertz.
  • Sample resolution is bits per sample.
  • Higher quality means a larger file.

Worked examples

Example 1

Explain what is meant by sample rate. [2 marks]

Working

The number of samples taken each second when recordingdefine the term
measured in hertz, with a higher rate capturing more of the wave's shapestate the unit and effect

Example 2

Explain why increasing the sample rate improves sound quality. [2 marks]

Working

More measurements are taken per second, so more of the original wave's shape is capturedstate what happens
making the digital recording a closer approximation to the original analogue soundexplain the effect on quality

Example 3

State the effect of increasing sample resolution on file size and explain. [2 marks]

Working

The file size increasesstate the effect
because more bits are used to store each individual sampleexplain why

Common mistakes

  • Confusing sample rate with sample resolution.

    Rate is samples per second; resolution is bits per sample.

  • Saying sampling makes a perfect copy.

    It is an approximation of a continuous wave.

  • Forgetting the file size trade-off.

    Higher quality always means more storage.

  • Giving the sample rate unit as bits.

    It is hertz, meaning samples per second.

Exam tips

  • Keep sample rate and resolution clearly distinct.
  • Use hertz for sample rate and bits for resolution.
  • Always mention the file size trade-off.
  • Say approximation rather than copy.

Key terms

Sampling
Measuring an analogue wave at regular intervals.
Sample rate
Samples taken per second, in hertz.
Sample resolution
The number of bits per sample.
Analogue
Varying continuously, unlike discrete digital values.

Related topics

Written and reviewed against the current AQA specification. Spotted an error? Let us know.