GCSE Computer Science • Data Representation

Sound Representation

Master how sound is digitised, understand sampling and bit depth, and calculate audio file sizes.

0
Activities
0
Correct
0
Streak 🔥

Key Concepts

Understanding how sound is converted from analogue to digital

🔊 Analogue Signal

Continuous wave with infinite possible values. Found naturally in the real world.

💾 Digital Signal

Discrete steps with finite values. Stored as binary data on computers.

Analogue Signal
A continuously changing signal that can be found in nature. Has infinite possible values between any two points.
Digital Data
The binary representation of an analogue signal. Consists of discrete values that can be stored on a computer.
Sampling
Taking a snapshot of an analogue signal at one single point in time. The amplitude is measured and recorded.
Sample Rate
The number of sound samples taken per second, measured in Hertz (Hz). CD quality = 44,100 Hz (44.1 kHz).
Sample Interval
The time between samples, measured in seconds. Calculated as 1 ÷ sample rate.
Bit Depth
The number of bits used to represent the value (amplitude) of each sample. More bits = more precision. CD = 16-bit.
Quantisation
Mapping a sampled reading/snapshot to the nearest available binary value based on the bit depth.
Amplitude
The value of the wave (y-axis) at a given point in time. Represents the loudness of the sound.
ADC
Analogue to Digital Conversion - the process of converting an analogue sound wave so it can be stored on a computer.
DAC
Digital to Analogue Conversion - the process of converting digital data back to an analogue signal for playback.
Nyquist Theorem
The sample rate should be at least twice the highest frequency in the sound to accurately reproduce it.
Stereo
Two audio channels (left and right) that create a spatial sound effect. Doubles the file size compared to mono.

📐 Sound File Size Formula

File Size (bits) = Sample Rate × Bit Depth × Duration (seconds)

For stereo: multiply by 2 (for two channels)
To convert: ÷8 for bytes, ÷1024 for KiB, ÷1024 again for MiB

🎧
Audio Quality Reference
Format Sample Rate Bit Depth Quality
Telephone 8,000 Hz 8-bit Low
CD Audio 44,100 Hz 16-bit High
DVD Audio 48,000 Hz 24-bit Very High
Studio 192,000 Hz 24-bit Professional
👂
Human Hearing Facts
20 Hz
Lowest frequency humans can hear
20,000 Hz
Highest frequency humans can hear
44.1 kHz
CD sample rate (Nyquist: 2 × 20kHz)

Sound Wave Visualizer

See how sampling and bit depth affect sound representation

🎵
Interactive Sampling Demonstration

📊 Sample Data

📈 Statistics

Sample Interval: 0.1s
Quantisation Levels: 16
Max Amplitude Value: 15
Binary Range: 0000 - 1111

Memory Match

Match the terms with their definitions

🧠
Find the Pairs

Click on cards to flip them. Match each term with its correct definition.

Parsons Puzzle

Arrange the steps in the correct order to calculate file size

🧩
Calculate file size in KiB for a 90-second audio at 44.1kHz, 16-bit

📦 Code Blocks

📝 Your Solution

Categorize

Drag items into the correct categories

📂
Sort These Sound Concepts

📦 Drag items from here:

File Size Calculator

Calculate audio file sizes and practice conversions

🧮
Calculate Audio File Size
❓
Practice Problems

Knowledge Check

Test your understanding with these exam-style questions