3.5.1 What is Sound and How Do Computers Process It?

In the real world, sound is a continuous wave that travels through the air. It is an analog signal, meaning it has infinite values and changes smoothly over time. However, computers do not work with analog signals. Instead, they work with digital data—numbers stored in binary (0s and 1s).

For a computer to store and process sound, the analog sound waves must be converted into digital form. This process is called sound sampling.

How Sound is Converted into Digital Data

1. A microphone records sound as an analog wave.
2. The computer captures “snapshots” (samples) of the wave at regular intervals.
3. Each sample is assigned a numerical value (binary representation).
4. The more samples taken per second, the better the digital sound quality.
5. The computer plays back the sound by reconstructing the wave from the stored samples.

This method allows computers to store and reproduce sound accurately while maintaining efficiency.

3.5.2 Understanding Sound Sampling

Since sound is a continuous wave, converting it to a digital format requires sampling—breaking the wave into discrete points. This is done at fixed intervals called the sample rate.

Key Terms in Sound Sampling

To understand digital sound, we need to explore two key concepts:

1) Sample Rate (Sampling Frequency)

• The sample rate refers to how many times per second the computer records a sound sample.
• Measured in Hertz (Hz) or kilohertz (kHz).
• A higher sample rate captures more details, resulting in better audio quality.

For example, a sample rate of 44.1 kHz means the computer takes 44,100 samples per second to represent the audio.

2) Bit Depth (Resolution of Sound)

• Bit depth determines how accurately each sample is recorded.
• It refers to the number of bits used to store each sample.
• Higher bit depth means better sound quality and more detailed recordings.

Each additional bit increases the possible range of values that can be assigned to a sound sample, making the digital sound more accurate.

Example of Bit Depth in Action

• 8-bit audio: Can store 256 different sound levels (2⁸ = 256).
• 16-bit audio: Can store 65,536 levels (2¹⁶ = 65,536).
• 24-bit audio: Can store 16,777,216 levels (2²⁴ = 16,777,216).

The higher the bit depth, the more precise the audio quality, but the file size will also increase.

3.5.3 How Digital Sound is Stored in a Computer

Once sound is sampled and converted into binary, it is stored in various file formats. Different formats balance sound quality and file size.

Common Audio File Formats

• Lossy Compression (MP3, AAC): Removes some audio details to reduce file size.
• Lossless Compression (FLAC, ALAC): Keeps all audio details while reducing file size.

For example, a 3-minute song in WAV format might be 30MB, while the same song in MP3 format might be only 5MB, but with slight quality loss.

3.5.4 Why Sound Sampling is Important

Advantages of Digital Sound Sampling

✅ High Accuracy – Digital audio can closely reproduce real-world sounds.
✅ Easy Storage & Sharing – Digital files can be easily copied, transferred, and stored.
✅ Editing & Processing – Computers can modify, mix, and improve digital audio.
✅ Compression & Streaming – Digital audio allows music to be streamed online efficiently.

Challenges of Digital Sound

❌ Large File Sizes – High-quality recordings take up a lot of storage.
❌ Data Loss with Compression – Lossy formats (MP3) reduce quality to save space.
❌ Hardware Limitations – Some devices have limited sound processing capabilities.

3.5.5 Real-World Applications of Sound Sampling

Sound sampling is used in various fields beyond just playing music. Some real-world applications include:

1) Music and Entertainment

• Digital sound is used in music production, concerts, and streaming platforms like Spotify and YouTube Music.
• Studio recordings use high bit-depth and sample rates to maintain quality.

2) Voice Assistants and Speech Recognition

• Virtual assistants like Siri, Google Assistant, and Alexa rely on digital sound processing to understand speech.
• AI-powered software converts spoken words into binary form and analyzes them.

3) Telecommunications

• Phone calls use compressed digital audio to efficiently transmit voice over networks.
• Older phone calls used 8 kHz sample rates, but modern VoIP (e.g., WhatsApp, Zoom) uses 16-48 kHz for clearer speech.

4) Movie Soundtracks & Special Effects

• In filmmaking, sound is recorded digitally and synced with video.
• Dolby Digital and DTS are used in cinemas for immersive surround sound.

5) Medical Applications

• Ultrasound imaging uses sound waves converted into digital form for diagnosis.
• Hearing aids process real-world sound digitally and adjust volume for clarity.

3.5.6 Summary: Key Takeaways

• Sound is originally analog and must be sampled into digital form for computers to store and process it.
• Sample rate (Hz) determines how many times per second sound is captured. Higher sample rates = better quality.
• Bit depth (bits per sample) defines how precisely each sound is stored. Higher bit depth = clearer sound.
• Digital audio files are stored in formats like WAV, MP3, and FLAC, balancing quality and file size.
• Sound sampling is essential in music, speech recognition, telecommunications, film, and medicine.

Looking Ahead

Understanding sound sampling prepares students for future topics in multimedia processing, AI-driven voice recognition, and digital communication technologies. In higher years (Year 8 and Year 9), students may explore:

• Advanced sound compression and encoding techniques.
• How sound is transmitted over the internet using streaming services.
• The role of sound in gaming and virtual reality.

By mastering the basics of digital sound, students build a strong foundation for working with multimedia in the digital world! 🎵💻