📚 Knowledge Library — Topic 1.3C — Data Representation

Sound Representation

Understand how real-world sound waves are sampled, converted into binary, and stored as digital sound files.

Start LearningWorked Example
1. Invitation

Sound starts as a wave.

Real-world sound is analogue. It changes smoothly and continuously over time.

A computer cannot store a smooth wave directly. It must measure the wave and convert those measurements into binary.

💡 Remember: analogue sound must be converted into digital data before a computer can process it.
Figure 1.1
Analogue to Digital
Sound wave
↓
Samples
↓
Binary
2. Big Idea

Sampling turns sound into numbers.

Sampling means measuring the amplitude of a sound wave at regular time intervals.

Each measurement is stored as a binary value. More measurements per second can create a more accurate digital recording.

💡 Sampling = measuring the sound wave at fixed intervals.
Figure 2.1
Sampling a Wave
~ ~ ~ ~ ~
•   •   •   •
↓
values stored
Each dot is one sample.
3. Bridge

Think of taking snapshots.

A video looks smooth because it is made from many still images shown quickly.

Sound sampling works in a similar way. More samples capture more detail from the original sound wave.

💡 More snapshots of the wave usually means smoother, more accurate playback.
Figure 3.1
Snapshot Model
Few samples
= rough sound

More samples
= smoother sound
4. Worked Example

What does 44,100 Hz mean?

Sampling rate is the number of samples taken per second. It is measured in Hertz.

Sampling rate: 44,100 Hz

44,100
samples
per second
44,100 measurements are taken every second.
Figure 4.1
Sampling Rate
Hz
=
samples per second
Higher rate = more measurements.
5. Bit Depth

Bit depth controls precision.

Bit depth, also called sample resolution, is the number of bits used to store each sample.

More bits per sample means more possible amplitude values, so the sound can be stored more precisely.

16-bit sound

2¹⁶ = 65,536 possible amplitude values
Figure 5.1
Bits per Sample
8-bit
= fewer levels

16-bit
= more levels
6. Exam Tip

Quality increases file size.

Higher quality sound usually uses a higher sampling rate and/or a higher bit depth.

🎯 Exam Tip: Higher sampling rate means more samples per second. Higher bit depth means more bits per sample. Both increase file size.
Figure 6.1
Sound File Size
sampling rate
× bit depth
× duration
↓
file size
7. Common Mistake

Sampling rate and bit depth are not the same.

Students often mix up these two terms.

⚠️ Common Mistake: sampling rate is how often samples are taken. Bit depth is how many bits are used to store each sample.
Figure 7.1
Do Not Mix Them Up
Sampling rate
= how often

Bit depth
= how precise
8. Summary

Sound representation in one screen.

Sound waves are analogue and continuous. Computers store digital data using binary values.

Sampling measures the wave at regular intervals. Sampling rate controls how many samples are taken each second.

Bit depth controls how many bits are used for each sample.

💡 Better sound quality usually means more data and a larger file size.
Figure 8.1
Digital Sound
analogue wave
↓
samples
↓
binary values