Thread Academy

Sound and Sampling

Learn how sound waves are sampled into digital audio.

  • Define and explain Sound and Sampling in your own words
  • Use key terms such as pixel accurately
  • Apply what you have learned to new examples and questions
  • Avoid the common mistakes learners make with this topic

This lesson focuses on Sound and Sampling: learn how sound waves are sampled into digital audio.

Definition: Sound and Sampling

Learn how sound waves are sampled into digital audio.

Key ideas

Everything is binary underneath

Text, images, sound and video are all stored as patterns of bits — the computer just interprets the patterns differently. The binary pattern 01000001 means the letter 'A' in text, but the same pattern could mean the number 65 or a dark pixel in an image. Meaning comes from context, not from the bits themselves.

More bits means more detail

With n bits you can represent 2 to the power of n different values: 8 bits give 256 colours or characters, while 24 bits give over 16 million colours. Higher colour depth, higher image resolution and higher sound quality all cost more bits — a trade-off between quality and file size.

Key term — pixel: The smallest dot in a digital image. Images are grids of pixels, each stored as a binary colour value.

Worked example: Sound and Sampling

A sound file sampled at a higher rate is larger. Why?

A higher rate takes more samples every second, so more numbers must be stored — better quality costs more bits.

Answer: A higher rate takes more samples every second, so more numbers must be stored — better quality costs more bits.

Common mistakes
  • Reading binary left to right as if the leftmost digit is worth 1 Correction: the rightmost column is always worth 1 — write the place values above the digits before adding.
  • Thinking 8 bits can store the number 999 Correction: 8 bits hold 0 to 255 only; larger numbers need more bits — check 2 to the power of n first.

Practice

Convert the binary number 1101 to denary.
Place values are 8, 4, 2, 1 — add the ones with a 1.

13 — that is 8 + 4 + 1.

Write denary 20 as a binary number.
The biggest place value that fits is 16.

10100 — that is 16 + 4.

How many different values can 4 bits represent?
Work out 2 to the power of 4.

16 — from 0 to 15.

The letter 'A' is stored as 01000001. What number is that in denary, and why might the same pattern mean something else elsewhere?
Convert, then think about context.

65 — and the same bits could be a colour value or part of an image, because meaning comes from how the program interprets the bits.

Quick check

Sound and Sampling — quick check

Which of these best defines "pixel"?

The smallest dot in a digital image. Images are grids of pixels, each stored as a binary colour value.

True or false: adding one more bit to a code doubles the number of values it can represent.

True — each extra bit doubles the combinations, since every existing pattern can end in either 0 or 1.
Key takeaways
  • Sound and Sampling: learn how sound waves are sampled into digital audio.
  • Everything is binary underneath: Text, images, sound and video are all stored as patterns of bits — the computer just interprets the patterns differently.
  • bit: A single binary digit — a 0 or a 1.
  • Watch out for: reading binary left to right as if the leftmost digit is worth 1
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