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Year 10
OCR

Calculation of sound file sizes

I can explain how sample bit depth and sample rate affect the size and quality of a sound file.

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New
New
Year 10
OCR

Calculation of sound file sizes

I can explain how sample bit depth and sample rate affect the size and quality of a sound file.

Download all resources
Share activities with pupils

Link copied to clipboard

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Lesson details

Key learning points

  1. Adjusting the sample bit depth when digitising sound affects the accuracy of the sound being captured.
  2. Adjusting the sample rate when digitising sound affects the completeness of the sound being captured.
  3. The file size of a sound file is determined from its sample bit depth, sample rate and duration.
  4. Selection of sample bit depth and rate depend on the use of the sound and the limitations imposed by the file size.

Keywords

  • Accuracy - how close a measurement is to its actual value

  • Duration - the length of time that something lasts

Common misconception

Any sound that is digitised is going to be noticeably different to the original sound.

When sound is turned into digital form with a high enough sampling rate and sample bit depth, the difference from the original sound is too small for human ears to notice.


To help you plan your year 10 computer science lesson on: Calculation of sound file sizes, download all teaching resources for free and adapt to suit your pupils' needs...

There are lots of examples of websites that provide audio of changable qualities. Find some music that pupils recognise and compare the difference in the quality to understand the effect sample rate and bit depth have on the perceived quality of audio.
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This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
What is a sound sample?
a type of music file
the number of bits used to represent sound
the speed of sound waves
Correct answer: a measure of a sound wave at a point in time
Q2.
What does digitisation mean?
converting sound waves into air vibrations
Correct answer: converting data into a binary sequence
taking fewer samples of sound
increasing the resolution of a sound file
Q3.
What does bit depth in sound sampling refer to?
the number of samples taken per second
the quality of a speaker
Correct answer: the number of bits used to represent a sample
the size of a sound file
Q4.
Put these steps in the correct order to digitise sound:
1 - measure the sound wave at a point in time
2 - convert the measurement into a binary sequence
3 - store the binary data
Q5.
What is the term used to describe the number of bits used to represent a sound sample?
Correct Answer: bit depth
Q6.
Match the terms with their definitions:
Correct Answer:sample,a measure of a sound wave at a point in time

a measure of a sound wave at a point in time

Correct Answer:digitisation,converting data into a binary sequence

converting data into a binary sequence

Correct Answer:bit depth,the number of bits used to represent a sample

the number of bits used to represent a sample

Exit quiz

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6 Questions

Q1.
What does adjusting the sample bit depth affect when digitising sound?
the completeness of the sound
Correct answer: the accuracy of the sound being captured
the duration of the sound file
the loudness of the sound
Q2.
What three factors determine the size of a sound file?
sample bit depth, duration and loudness
sample rate, accuracy and loudness
Correct answer: sample rate, duration and sample bit depth
completeness, accuracy and duration
Q3.
What happens if the sample rate is too low?
the sound file becomes larger
the accuracy of the sound improves
the sound becomes louder
Correct answer: the sound quality decreases
Q4.
What is the effect of increasing both sample rate and sample bit depth?
the file size decreases, and the sound quality improves
Correct answer: the file size increases, and the sound quality improves
the file size stays the same, and the sound quality improves
the sound becomes quieter
Q5.
Calculate the file size in kB of a 2-minute sound recording that has a sample rate of 2000 Hz and a sample bit depth of 6 bits.
Correct Answer: 180 kB, 180kB, 180, 180 kb, 180kb
Q6.
Calculate the file size in kB of a 3-minute sound recording that has a sample rate of 1000 Hz and a sample bit depth of 2 bits.
Correct Answer: 45 kB, 45kB, 45, 45kb, 45 kb