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COSC1078 Introduction to Information Technology Lecture 5 Audio

James Harland james.harland@rmit.edu.au. COSC1078 Introduction to Information Technology Lecture 5 Audio. 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)

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COSC1078 Introduction to Information Technology Lecture 5 Audio

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

  2. Intro 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. Intro to IT Overview • Questions? • Assignment 1 • Audio • Questions?

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

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

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

  7. Intro 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. Intro 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. Intro to IT Assignment 1

  10. Overview 01010100001010101010100110100010101001101001010010100011100010101010100101111001001010… Lecture 5: Audio Intro to IT

  11. 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’’  ) Lecture 5: Audio Intro to IT

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

  13. 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 (I1/I2) I1 = 20, I2 = 10: # decibels = 10 x log 2 = 3 I1 = 100, I2 = 10: # decibels = 10 x log 10 = 10 I1 = 400, I2 = 4: # decibels = 10 x log 100 = 20 Lecture 5: Audio Intro to IT

  14. 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 (1012 x louder than 0 db !!) Lecture 5: Audio Intro to IT

  15. Sound waves Lecture 5: Audio Intro to IT

  16. Sound waves Lecture 5: Audio Intro to IT

  17. Overview 01010100001010101010100110100010101001101001010010100011100010101010100101111001001010… Lecture 3: Images Intro to IT

  18. Digitising Sound Sampling: how often discrete readings are taken (from a continuous signal) Lecture 5: Audio Intro to IT

  19. 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 Lecture 5: Audio Intro to IT

  20. 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 Lecture 5: Audio Intro to IT

  21. 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 Lecture 5: Audio Intro to IT

  22. Intro to IT Conclusion • Go to laboratory classes (and tutorials) this week! • Work on Assignment 1 • Keep reading! (book particularly)

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