Decibel System & Data Rate
The decibel system is used to measure sound intensity
and loudness, while data rate defines the amount of
audio data processed or transmitted per second in
digital audio systems.
1. Introduction
Sound intensity varies over a wide range, so a logarithmic scale called decibel (dB) is used. Data rate helps determine audio quality and storage size.
- Decibel measures loudness
- Data rate affects audio quality
2. Decibel (dB)
Decibel is a logarithmic unit used to express the ratio of sound intensity or power relative to a reference level.
- Logarithmic scale
- Represents large intensity ranges
3. Sound Intensity Level
Sound intensity level indicates how loud a sound is perceived by the human ear.
- Measured in decibels
- Based on reference intensity
4. Decibel Scale
- 0 dB – Threshold of hearing
- 30 dB – Whisper
- 60 dB – Normal conversation
- 90 dB – Traffic noise
- 120 dB – Threshold of pain
5. Advantages of Decibel Scale
- Handles wide sound range easily
- Matches human hearing response
- Simplifies calculations
6. Data Rate
Data rate is the amount of digital audio data processed or transmitted per second.
- Measured in bits per second (bps)
- Also called bit rate
7. Factors Affecting Data Rate
- Sampling rate
- Bit depth
- Number of channels
8. Data Rate Formula
Data Rate = Sampling Rate × Bit Depth × Channels
Example: 44.1 kHz × 16 bits × 2 channels = 1411.2 kbps (CD quality)
9. Importance
- Controls audio quality
- Affects file size
- Important for streaming
10. Applications
- Audio recording and playback
- Music streaming platforms
- Broadcasting
- Multimedia systems
Practice Questions
- What is decibel?
- Why is decibel scale logarithmic?
- Define data rate.
- State the data rate formula.
- How does data rate affect audio quality?
Practice Task
Explain with examples:
✔ Decibel scale values
✔ Calculating audio data rate
✔ Impact of bit rate on sound quality