1. Lecture 5: Audio Intro to IT COSC1078 Introduction to Information Technology Lecture 5 Audio James Harland james.harland@rmit.edu.au

2. Lecture 5: AudioIntro to IT Introduction James Harland Email: james.harland@rmit.edu.au URL: www.cs.rmit.edu.au/~jah Phone: 9925 2045 Office: 14.10.1 (Building 14, level 10, room 1) Consultation: Mon 4.30-5.30, Thu 11.30-12.30 What is the view like from my office?

3. Lecture 5: AudioIntro to IT Overview  Questions?  Assignment 1  Audio  Questions?

4. Lecture 4: ImagesIntro to IT Introduction to IT 1 Introduction 2 Images 3 Audio 4 Video WebLearnTest 1 5 Binary Representation Assignment 1 6 Data Storage 7 Machine Processing 8 Operating Systems WebLearn Test 1 9 Processes Assignment 2 10 Internet 11 Internet Security WebLearn Test 3 12 Future of ITAssignment 3, Peer and Self Assessment

5. Lecture 5: Audio SE Fundamentals Questions? How did you spend 6-8 hours on this course last week? This week?

6. Lecture 5: AudioIntro to IT Assessment Process  Submit all assignments via Blackboard in the Learning Hub  Assignment 1due 11.59pm Sunday 1 st April  Assignment 2due 11.59pm Sunday 6 th May  Assignment 3 due 11.59pm Sunday 27 th May  Late assignments attract a penalty of 10% per day late, up to a maximum of 50%

7. Lecture 5: AudioIntro to IT Assignment  Assignment will be in three parts  Overall task is to produce a video  Groups of up to 3  Assessed by final video and group blog  Part 1: images and audio (end of week 5)  Part2: hardware (end of week 9)  Part 3: reflection, research (end of week 12)

8. Lecture 5: AudioIntro to IT Assignment 1  Use GIMP (or a similar tool) to perform some manipulations on an image  Use Audacity to perform some manipulations on sound  Use a movie making tool to produce something like (and much better than!) ‘Lord of the Controllers 1 & 2’  Email me your group and its name so that I can set up a blog on the Learning Hub

9. Lecture 5: AudioIntro to IT Assignment 1

10. Lecture 5: AudioIntro to IT Overview 01010100001010101010100110100010101001101001010010 100011100010101010100101111001001010…

11. Lecture 5: AudioIntro to IT What is sound?  Vibrations in a medium (air, water, … )  Disturbances in the medium propagate away from the source  Modelled mathematically as waves  Does not travel in a vacuum (``In space, no-one can hear you swear’’ )

12. Lecture 5: AudioIntro to IT Frequency  How many complete cycles within a unit of time  Higher frequency means higher pitch

13. Lecture 5: AudioIntro to IT Sound intensity How can you measure loudness? Can measure power/energy/voltage per unit area Standard unit of comparison is bel or decibel #decibels = 10 x log (I 1 /I 2 ) I 1 = 20, I 2 = 10: # decibels = 10 x log 2 = 3 I 1 = 100, I 2 = 10: # decibels = 10 x log 10 = 10 I 1 = 400, I 2 = 4: # decibels = 10 x log 100 = 20

14. Lecture 5: AudioIntro to IT Sound intensity  Strictly speaking decibel is a relative unit only  For humans, it only makes sense as “relative to the softest sound a human ear can hear”  0 db is baseline (not silence, or no sound …)  Often threshold of hearing at 1000Hz  Threshold of pain is 120 db (10 12 x louder than 0 db !!)

15. Lecture 5: AudioIntro to IT Sound waves

16. Lecture 5: AudioIntro to IT Sound waves

17. Lecture 3: ImagesIntro to IT Overview 01010100001010101010100110100010101001101001010010 100011100010101010100101111001001010…

18. Lecture 5: AudioIntro to IT Digitising Sound Sampling: how often discrete readings are taken (from a continuous signal) Rate (Hz)Quality 11,025AM Radio 22,050FM Radio 44,100CD 48,000DAT 96,000-192,000DVD

19. Lecture 5: AudioIntro to IT How often to sample? Nyquist (or Nyquist-Shannon): Need to sample at least two points in each cycle to perfectly reconstruct the sound wave Humans can hear approximately 20 to 20,000 Hz Most sensitive in range 2,000 Hz to 5,000 Hz 11,025 Hz often works for speech (up to 5,000 Hz) but not music

20. Lecture 5: AudioIntro to IT Quantisation Once we have a sample, how many different values do we allow for it? More values means better quality, but larger file size BIT DEPTH

21. Lecture 5: AudioIntro to IT Quantisation Same issues as for images: More sampling, more quantised levels  better quality  larger file size Dynamic range:  range of possible quantised values  will `clip’ some sounds if too narrow  will waste accuracy if too wide

22. Lecture 5: AudioIntro to IT Conclusion  Go to laboratory classes (and tutorials) this week!  Work on Assignment 1  Keep reading! (book particularly)