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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 514 exam-style questions, each with its mark scheme and example answers. Print it, or answer it on paper and then open the mark schemes. Or browse the questions by topic.

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2 questions · 3 marks

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1Short recall1 markSound Swap Remove

A digital sound representation is created by sampling an analogue sound wave.

State one way the accuracy of this representation can be increased.

[1 mark]
Mark scheme

Award one mark for any of the following:

  • Increase the sample rate / take more samples per second (1)
  • Increase the bit depth/sample resolution / use more bits per sample (1)
  • Decrease the sample interval (1)

Do not accept increase the amplitude/volume

Do not accept decrease the sample rate / increase the sample interval

Example answers and how they were marked
Full marks1/1

Increase the sample rate.

Why: Creditworthy point: increase the sample rate (1).

No marks0/1

Decrease the sample rate.

Why: Near-miss: decreasing the sample rate reduces accuracy, so no mark; the mark scheme's do-not-accept line covers this (0).

No marks0/1

Increase the volume of the sound.

Why: Misconception: loudness/amplitude is not a way to increase sampling accuracy; do not accept increase amplitude/volume (0).

2Explain2 marksSound Swap Remove

Each sample of a sound wave is stored as a binary number.

Explain how increasing the bit depth affects the representation of a sound wave.

[2 marks]
Mark scheme

Award up to two marks for a linked explanation such as:

  • Each sample is stored using more bits (1) so the amplitude can be recorded more precisely (1)
  • More different amplitude values can be represented (1) because each extra bit doubles the number of possible values (1)
  • The height of the wave at each sample point is measured more accurately (1) so the digital wave is closer to the analogue wave (1)
  • The gap between the true amplitude and the stored value is smaller (1) because there are more values for the sample to be rounded to (1)

For both marks, the expansion must follow/associate with the statement.

Do not accept 'the sound is sampled more often' or 'more samples are taken per second', as these describe the sample rate, not the bit depth.

Do not accept 'the file size increases' on its own as an effect on the representation of the sound.

Example answers and how they were marked
Full marks2/2

Each sample is stored using more bits, so the amplitude at each sample point can be recorded more precisely.

Why: Point (more bits per sample) (1) with linked reason (amplitude recorded more precisely) (1).

Some marks1/2

Each sample is stored using more bits.

Why: Creditworthy point (1) but no linked effect on the accuracy of the representation, so only one mark.

No marks0/2

It takes more samples every second, so the wave is stored in more detail.

Why: Confuses bit depth with sample rate, so no mark is awarded.

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