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1CP2-P-9.3 Sampling analogue sound into binary

Part 3 of 6 · 1CP2-P-9 · Bitmap, sound and compression

Sound in air varies continuously. A microphone produces an analogue signal. An analogue-to-digital process measures amplitude at regular times, rounds each measurement to an available level and stores the level as a binary code.

Students will:

  • describe sampling from an analogue signal into binary
  • distinguish sample rate from sample interval
  • explain how sample rate and bit depth affect representation
  • order the stages of analogue-to-digital conversion

Inside: 6 explanation cells, 1 fill-in-the-blanks cell, 2 multiple-choice questions and 3 written answers. 12 marks, about 45 minutes.

Series: 1CP2-P-9 · Bitmap, sound and compression, part 3 of 6.

Shared by Coding PathwayVerified teacher

  • 12 cells
  • About 45 minutes
  • CC BY-SA 4.0
  • Shared 17 Aug 2026

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The whole resource, exactly as a class sees it. Answers and marking are held back.

Sampling analogue sound into binary

Sound in air varies continuously. A microphone produces an analogue signal. An analogue-to-digital process measures amplitude at regular times, rounds each measurement to an available level and stores the level as a binary code.

1. Build the representation

Sampling analogue soundanalogue waveform (blue); regular samples (orange)sample rate = samples each second; interval = time between samples

Sample rate is measurements per second. Sample interval is time between measurements. Bit depth controls the number of amplitude levels: n bits give 2^n levels. Rate changes time detail; depth changes amplitude precision.

Fill in the blanks3 marks
The number of measurements each second is sample gap 1. Time between measurements is the sample gap 2. Bits per sample are the bit gap 3.
  • depth
  • interval
  • rate
Multiple choice1 mark

Which change creates more samples each second?

  • AIncrease sample rate
  • BIncrease sample interval
  • CDecrease bit depth
  • DReduce amplitude

2. Worked method

At 4 samples per second, the interval is 1/4 second. Increasing to 8 samples per second halves the interval to 1/8 second. With 3-bit depth, each measured amplitude is rounded to one of 8 available levels.

Written answer3 marks

Put these stages in order: store binary codes; measure amplitude regularly; microphone creates analogue signal; round to an available level.

State the complete sequence.

Students type their answer here.

Written answer2 marks

Explain how increasing sample rate can improve fidelity.

Link time spacing to waveform changes.

Students type their answer here.

3. Apply and check

Write the formula or reasoning step before substituting values. Keep the representation, the measurement and its units distinct.

Written answer2 marks

Explain how increasing bit depth can improve fidelity.

Link levels to rounding.

Students type their answer here.

Multiple choice1 mark

Which statement is correct?

  • AAmplitude determines pitch only
  • BDigital recording stores every point of the analogue curve exactly
  • CBit depth changes amplitude levels, not sampling frequency
  • DSample interval is samples per second

Examination method

Show relevant working, label units and answer the command word. A number without its meaning or unit may not demonstrate the required method.

Route forward

Next you will use sample rate, bit depth and duration to calculate uncompressed sound size.