3g Representing Sound

• Understand that sound is analogue and that it must be converted to a digital form for storage and processing in a computer.
• Understand that sound waves are sampled to create the digital version of sound.
• Describe the digital representation of sound in terms of:
  • sampling rate
  • sample resolution.
• Calculate sound file sizes based on the sampling rate and the sample resolution.

3g Representing Sound

• The sound wave is converted to an analogue voltage.
• This analogue voltage is sampled.
• The value of this voltage is converted to a binary value.
• This binary value can then be processed and/or stored.
• The reverse is done to output the sound from the computer. 

Sample Resolution

• Also called bit depth
• Image resolution affects the quality of an image allowing the image to capture more of the variation in light.
• Audio sample resolution affects the quality of a sound allowing more variation in the sounds that can be recorded.

Sample Resolution

Sample Resolution

• The higher the sample resolution the better the sound reproduction.
• The higher the sample resolution the larger the sound file.
  • 2-bit sound allows four different sound values
  • 4-bit sound allows sixteen different sound values
  • 8-bit sound allows 256 different sound values
  • 16-bit sound allows 65,536 different sound values

Sample Rate

The number of times (per second) that a measurement is made is called the sample rate.

Sample Rate

Sample Rate

• The higher the sample rate the higher quality of sound will be produced.
• The higher the sample rate the larger the file size.
• A high quality sound is usually sampled at 44.4 kHz (44,100 samples per second).
• This is about twice the frequency a human can hear.

Questions

1. What is meant by the term sample resolution?
2. What is the formula that relates file size, sampling rate, sampling resolution and length?
3. Outline how an analogue sound wave can be converted into digital data and how quality is lost during the conversion.
4. How does increasing the sample rate improve the quality of the sound?
5. Explain why sound is not always sampled using settings that give the highest possible quality.
6. A 200 second piece of audio is sampled using a sampling rate of 30 Hz and a sample resolution of 10 bits. What is the file size of the sampled audio?

Answers

1. What is meant by the term sample resolution?

2. What is the formula that relates file size, sampling rate, sampling resolution and length?

3. Outline how an analogue sound wave can is converted into digital data and how quality is lost during the conversion.

Answers

4. How does increasing the sample rate improve the quality of the sound?

5. Explain why sound is not always sampled using settings that give the highest possible quality.

Answers

6. A 200 second piece of audio is sampled using a sampling rate of 30 Hz and a sample resolution of 10 bits. What is the file size of the sampled audio?

3g Representing Sound

• Understand that sound is analogue and that it must be converted to a digital form for storage and processing in a computer.
• Understand that sound waves are sampled to create the digital version of sound.
• Describe the digital representation of sound in terms of:
  • sampling rate
  • sample resolution.
• Calculate sound file sizes based on the sampling rate and the sample resolution.