Sound Representation

1. How Sampling Works

Sound in the real world is Analogue (continuous). Computers are Digital (binary). To store sound, we must convert it using a process called Sampling.

The 4 Mandatory Steps:

1. Sample the Wave: The analogue sound wave is measured.
2. Set Intervals: Measurements are taken at regular, fixed time intervals (e.g., every 0.001 seconds).
3. Measure Amplitude: The Amplitude (height) of the wave is recorded.
4. Binary Conversion: The amplitude value is converted into a unique binary number.

2. Sample Rate (Hz)

Definition: The number of times per second the amplitude is measured.

Measured in: Hertz (Hz).

Action	Effect on File Size	Effect on Quality
Increase Rate (e.g., 44kHz)	📈 Increases (More data to store)	✅ Better / Truer (Closer to original wave)
Decrease Rate (e.g., 8kHz)	📉 Decreases	❌ Worse (Choppy / Less accurate)

3. Bit Depth

Definition: The number of bits available to store each individual sample.

Why does it matter?

Think of Bit Depth as the "ruler" used to measure the wave height.

• Low Bit Depth: A ruler with only inches. (Inaccurate measurements).
• High Bit Depth: A ruler with millimeters. (Very precise measurements).

Increasing Bit Depth increases the Dynamic Range—meaning a wider range of loud and quiet sounds can be accurately recorded.

⚡ Practice Questions

Test your knowledge with these exam-style questions.

Q1: Describe how an analogue sound wave is converted to digital. [3 marks]

Answer:

• The amplitude/height of the wave is measured [1].
• At set/regular intervals [1].
• Each measurement is stored as a binary number [1].

Q2: Explain two effects of increasing the Sample Rate. [2 marks]

Answer:

1. The file size will increase (because there are more samples to store).
2. The quality will improve (because the digital wave is closer to the original analogue wave).

Q3: Layla stores 1MB images on a 3GB drive. How many can she store? [2 marks]

Calculation:

1. Convert GB to MB: 3 GB = 3000 MB.

2. Divide: 3000 / 1 = 3000 images.