1. Data Representation: Sound

2. Hearing Aid (Microphone)

3. Light Sensor

4. Heat Sensor

5. Question: What do they all have in common?

6. Lesson Objectives All Most Some We are learning today:
The basic concept of analogue / digital data
How computers store data about sound, temperature
and light.
What is meant by the term “Bit Sampling”
What is meant by the term “Bit Resolution”
What is meant by the term “Bit Rate”
How the bit sampling / bit rate affect file sizes
All Most Some

7. The basic concept of analogue / digital data
Digital signals are discrete (not
continuous)
They are either OFF or ON
In binary terms 0 or 1
Analogue signals continuous (infinite possibilities)
Affected by noise
The basic concept of analogue / digital data

8. What does it mean by continuous?
Vinyl Record CD
The basic concept of analogue / digital data

9. The basic concept of analogue / digital data
Digital vs Analogue
The basic concept of analogue / digital data

10. Sample Rate
The number of samples of sound taken by a computer, which represents sound digitally, in a second.
What is meant by the term “Sample Rate”

11. Sample Rate CD’s currently have a sample rate of 44100 Hhz or 44khz.
Which means the sound is sampled at times a second.
What is meant by the term “Sample Rate”

12. Sample Rate What is meant by the term “Sample Rate” Reading Volt
.10 sec -1
.25 sec 1
.40 sec 7
.55 sec 6
.70 sec 5
.85 sec 2
1.00 sec
Signed Binary
What is meant by the term “Sample Rate”

13. A single square on an image is a pixel.

14. Bit / Colour Depth
Any black / white images have a colour / bit depth of 1-bit.
The pixel is either white or black.

15. These are 8 bit /16 bit images.
Bit / Colour Depth
These are 8 bit /16 bit images.
This means a pixel can choose between or
colours.

16. Bit / Colour Depth
To store true colour (photo quality) you need at least 24bit (from 0 – 16 million colours).

17. Each pixel in this image stores the colour code: 9F7FA8

18. What is the sample resolution this?
Remember: I used 1 ‘I’ for each sample. The number of bits assigned to each sample.
What is the sample resolution this?
Reading
Volt
.10 sec -1
.25 sec 1
.40 sec 7
.55 sec 6
.70 sec 5
.85 sec 2
1.00 sec
1.15 sec -3
Signed Binary
8 bits
What is meant by the term “Sample Resolution”

19. Bit Rate
Bit Rate – The number of bits required to store 1 second of sound.
This is then played back at Mbps (Megabits per second)
What is meant by the term “Bit Rate”

20. What is the bit rate for this?
Bit Rate – The number of bits required to store 1 second of sound.
This is then played back at Mbps (Megabits per second)
Reading
Volt
.10 sec -1
.25 sec 1
.40 sec 7
.55 sec 6
.70 sec 5
.85 sec 2
1.00 sec
1.15 sec -3
Signed Binary
What is the bit rate for this?
56Mbps
What is meant by the term “Bit Rate”

21. Recap Sample Rate – No of samples per second
Sample Resolution – No of bits assigned to each sample
Bit Rate – Amount of bits for 1 second of sound
What is meant by the term “Bit Rate”

22. File Size Sample Rate = 8000Hz Sample Resolution = 16 bit
File Size = Sample Rate * Sample Resolution * Length of sound
Sample Rate = 8000Hz
Sample Resolution = 16 bit
Length of Sound = 30 seconds
8000 * 16 * 30 = bits or bytes
How to calculate a file size

23. How can the different rate effect the sound quality.
8khz
22khz
44khz
How the bit sampling / bit rate affect file sizes.