Sample sound into binary
Describe digital sound sampling and explain how sample rate and sample resolution affect accuracy and file size.
This sequence follows Cambridge IGCSE Computer Science 0478, 2026–2028 syllabus Version 6. It covers subject content sections 1.1–1.3 only. The separately published 2029–2031 syllabus is not mapped here. Practice is original, self-checked and does not award an official Cambridge grade. Full timed papers and human subject-teacher review remain outstanding.
Before you begin
- No programming language is required. Be comfortable with place value and multiplication; each lesson introduces the computer-science notation it uses.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does an 8 kHz sample rate mean?
What you will learn
- Explain how a sound wave is sampled
- Distinguish sample rate from sample resolution
- Predict how either setting changes accuracy and file size
Sampling turns a wave into measurements
A microphone produces a changing sound wave. A computer samples its amplitude at regular time intervals and stores each measurement as a binary value.
Sample rate is the number of samples taken each second. Sample resolution is the number of bits used for each sample. Increasing either generally improves the representation's accuracy and increases file size.
The settings solve different limits
A higher sample rate records more moments in each second, so rapid changes are captured more closely. A higher resolution provides more possible amplitude levels for each moment. Neither setting is the duration of the recording.
Pause and explain
What is the likely effect of raising sound sample resolution while holding the sample rate fixed?
Worked example
A recording changes from 8 kHz, 8-bit samples to 16 kHz, 8-bit samples. What changes?
Show the worked solution
- The sample rate doubles, so twice as many samples are stored each second.
- Resolution stays at 8 bits per sample.
- For the same duration and channel count, the uncompressed file size doubles.
Answer The higher rate captures more samples per second and can represent changes more accurately; file size doubles if duration and channel count stay fixed.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A one-second mono recording uses 4,000 samples. State its sample rate.
Give me a hint
Sample rate is samples per second.
Compare my reasoning
- There are 4,000 samples in one second.
- So the rate is 4,000 samples per second or 4 kHz.
4 kHz
Look for these in your work
- Per-second unit used
- Rate equals 4 kHz
A 10-second recording changes from 22,050 Hz, 8-bit mono to 22,050 Hz, 16-bit mono. What happens to uncompressed file size?
Give me a hint
Use the audio-size relationship; only bits per sample change.
Compare my reasoning
- The sample rate is unchanged.
- Bits per sample double from 8 to 16.
- For the same duration and channel count, the file size doubles.
It doubles.
Look for these in your work
- Changed variable identified
- Proportional effect stated
A wildlife researcher wants to capture high-pitched bird calls but keep files manageable. Explain the trade-off when choosing the sample rate and resolution.
Give me a hint
Mention what each setting captures and its storage cost.
Compare my reasoning
- Higher sample rate captures more changes each second.
- Higher resolution distinguishes more amplitude levels.
- Increasing either setting raises uncompressed file size, so the researcher balances fidelity against storage and transmission limits.
Higher sample rate and resolution can improve accuracy, but both increase file size. Choose settings high enough for the calls being studied while respecting storage and bandwidth limits.
Look for these in your work
- Rate effect
- Resolution effect
- Storage trade-off
Common mistakes
- Confusing sample rate with bits per sample
- Claiming that increasing resolution gives more samples each second
What can you explain now?
Which setting controls how many amplitude levels are available for each sound sample?
Compare with the explanation
Sample resolution
More bits per sample allow more possible encoded amplitude levels.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Which sound setting controls samples per second, and which controls bits per sample?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.