This key facts covers Sound Representation - Digital Audio within Images & Sound for GCSE Computer Science. Revise Images & Sound in 3.3 Data Representation for GCSE Computer Science with 18 exam-style questions and 16 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 7 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Sound Representation - Digital Audio
How Digital Sound Works:
- Analog sound: Continuous wave (air pressure changes)
- Sampling: Measure amplitude (loudness) at regular intervals
- Digital sound: Series of numbers representing amplitude snapshots
- Playback: Convert numbers back to sound waves through speakers
Key Sound Properties:
1. Sample Rate (Samples per Second / Hz):
- 8,000 Hz: Telephone quality (low)
- 22,050 Hz: AM radio quality
- 44,100 Hz (44.1 kHz): CD quality (standard)
- 48,000 Hz: DVD/video standard
- 96,000 Hz or 192,000 Hz: Studio/hi-res audio
- Higher sample rate: Captures more detail, better quality
2. Bit Depth (Bits per Sample):
- 8-bit: 256 loudness levels (low quality, hissy)
- 16-bit: 65,536 levels (CD quality)
- 24-bit: 16.7 million levels (studio quality)
- 32-bit: Professional recording
- Higher bit depth: More dynamic range, quieter background noise
3. Channels (Mono vs Stereo):
- Mono: 1 channel (single audio stream)
- Stereo: 2 channels (left and right, surround effect)
- Surround: 5.1, 7.1 (multiple speakers)
4. Duration (Length in Seconds):
- Longer duration = more samples = larger file
Practice questions for Images & Sound
What does colour depth refer to in a digital image?
Explain the effect of increasing colour depth on a digital image. Refer to both file size and image quality in your answer.