Lecture Notes: Sound Storage in Computers

Introduction

• Focus on Chapter about Text, Images, and Sound.
• Today's focus: Sound, how it is stored in computers.

What is Sound?

• Sound is analog data and a form of wave, specifically vibrations.
• Computation of sound involves converting it into a format the computer understands.

Analog vs Digital Data

• Analog Data: Continuous wave data, difficult for computers to interpret.
  • Example: Continuous waveform where each second has different values.
• Digital Data: Discrete data points, easier for computers to interpret.
  • Continuous wave is sampled at regular intervals to create digital data.

Sampling

• Definition: Process of converting analog data into digital by taking discrete points at regular intervals.
• Converts pure line data (analog) into stepped data (digital).
• Loss and Addition: During conversion, some data (blue) is lost, and some extra data (green) is added.
• Improvement: Increasing the number of samples reduces loss and added data.
  • Example: More samples per second lead to better approximation of original data.

Sampling Rate

• Definition: Number of samples taken per second.
• Effects:
  • Higher sampling rate: Sound is closer to the original, fewer errors, requires more storage.

Sampling Resolution

• Definition: Number of bits assigned per sample.
• Effects:
  • Higher resolution: Greater volume range, better quality, but more storage required.
  • Example: High pitch or bass sounds require more bits per sample.
• Calculation:
  • File size = Sampling Rate × Sampling Resolution × Length of Sound (in seconds).
  • Example: 320 Kbps vs 128 Kbps sound quality.

Practical Example

• Human Voice Recording: Requires around 8000 samples/second for good quality.
• Music Recording: Requires 32,000 to 44,000 samples/second for preserving quality.
• Different Modes: Different sampling rates are used for various applications like phone calls vs music.

Summarized Topics

1. Sampling - Digital approximation by marking discrete points to convert analog sound into digital at regular intervals.
2. Sampling Rate - Number of samples taken per second, affects closeness to original sound and error rate.
3. Sampling Resolution - Number of bits per sample, affects volume range and quality of sound.

Example Calculation and Units

• Smallest Unit: Bit (B), proceeds to Byte, Kilobyte (KB), Megabyte (MB), Gigabyte (GB), etc.
• Conversion based on powers of 1024.

Homework and Further Reading

• Question: Explain how sound is stored in a computer.
• Related Topics: Text and Image storage in computers.
• Next Class Topic: Data Storage and Compression

Note: Pay attention to the conceptual difference between how human senses and computers perceive and store data.