Digital Television & Home Theater - PowerPoint PPT Presentation

Gabriel
slide1 l.
Skip this Video
Loading SlideShow in 5 Seconds..
Digital Television & Home Theater PowerPoint Presentation
Download Presentation
Digital Television & Home Theater

play fullscreen
1 / 103
Download Presentation
Digital Television & Home Theater
416 Views
Download Presentation

Digital Television & Home Theater

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Digital Television & Home Theater • Audio for Video • Basic Acoustics • How & Why We Hear • Movie & Home Theater Sound-System Configurations, Including Surround Sound • Digital Audio Formats: the Good, the Bad, and the Sublime.

  2. Sound Basics: What Is Sound? • Sound = Traveling Waves Of Air Pressure • Air Pressure Wave: Localized, Temporary, Sequential Increase + Decrease in Air Pressure Around Normal (15 lbs./sq. inch) • Each Wave Must Have Both A Positive (pressure increase) And Negative (pressure decrease) Part • Overall Air Pressure Cannot Change • Think Of Air Molecules Temporarily Bunching Up In Some Places and Spreading Out In Others. The Bunching Up Spreads Like Falling Dominos

  3. From William Vennard: Singing The Mechanism & The Technique

  4. Sound Basics: Frequency • A Sequential Increase & Decrease In Pressure Is Called A Cycle. • Think of It As A Single Wavelet. • A Cycle Takes A Finite Time To Complete • Pressure Variation Goes 0 + 0 - 0, or 0 - 0 + 0 • Sustained Sounds With Repetitive Identical Cycles Have An Associated Fundamental Frequency, F • F = The Number Of Cycles Occurring Within A Second Of Time • Expressed in Hz. = Cycles/Second

  5. Sound Basics: Auditory Perception • When Sustained Sounds With Repetitive Air Pressure Waves Are Perceived By The Ear, They Give The Sensations Of Pitch & Loudness • More Cycles In A Given Span Of Time = Higher Pitched Sound • The Greater The Increase & Decrease In Air Pressure Variation Within Each Cycle = The Louder The Sound

  6. Sound Basics: Hearing Range • Pitch Is Perceived Logarithmically In Octaves • One Octave Increase = Doubling The Frequency • Human Hearing Covers 10 Octaves, From 20 Cycles/Second to 20,000 Cycles/Second • Everyday Sounds Are Usually 40 Cycles/Second to 12,000 Cycles/Second • The Critical Band For Speech Recognition is 500 Cycles/Second to 2,000 Cycles/Second

  7. Sound Basics: Wavelength • Air Pressure Waves Travel ~ 1,130 ft./sec. • A Cycle Of Air Pressure Variation That Takes A Finite Time To Complete Therefore Spreads Out Across a Finite Distance = It’s Wavelength • Sustained Sound With Repetitive Identical Cycles Having Fundamental Frequency F, Have Wavelength L Derived By: L Ft./Cycle = 1.13 Ft./Millisecond / F Cycles/Second • Note That The Higher The Frequency (& Pitch), The shorter The Wavelength

  8. Resonation & Perception • Several Air Pressure Waves Simultaneously Traveling Through The Same Space Will Add Together Linearly. • So Will Traveling Air Pressure Waves When Trapped Between Two Physical Parallel Boundaries. • At Each Boundary Some Sound Passes Through But Most Bounces In The Reverse Direction • The Waves Will Continue To Bounce Back And Forth Between Boundaries Until All The Sound Has Leaked Out. • Sustained Sounds Will Continually Feed New Air Pressure Waves To Bounce And Add Together Between The Boundaries

  9. Sound(Air Pressure)- Waves Trapped Between Parallel Walls Of A Resonator Sound Leakage

  10. Resonation & Perception • For Most Frequencies, Multiple Bouncing Pressure Waves Will: • Momentarily Reinforce Each Other Some Places • Momentarily Oppose Each Other At Other Places • But With No Consistent Pattern.

  11. Resonation & Perception • However, At A Few Frequencies Bouncing Pressure Waves Will Constantly Reinforce Each Other And Always At The Same Places • These Places Of Constantly Reinforcing Pressure Waves Are Called “Standing Waves”. • As Standing Waves Build In Intensity With Sustained Sound, More Sound “Leaks” Through The Boundaries To The Outside Until Equilibrium Is Reached.

  12. 1 2 Long-Term Average 3 Standing Waves

  13. Resonation & Perception • Which Frequencies Will Produce Standing Waves? • Only Those For Which The Distance Between Boundaries Is An Integer Multiple Of The Frequency’s Wavelength • I. E. When 1, 2, 3, 4, ... Wavelengths Will Perfectly Fit Between The Boundaries With No Pieces Left Over.

  14. Resonation & Perception • Parallel Physical Boundaries Therefore Act As A Resonator & Filter. Put Sustained Broadband Noise In (Which Contains Many Frequencies): • Most Frequencies Will Be Attenuated. • A Few Will Be Strengthened and Projected. • The Frequencies That Are Strongly Resonated Reveal The Dimensions Of The Resonator.

  15. Resonation & Perception • Real-World Hollow Objects Are 3-Dimensional & Have Many Non-Parallel Boundaries • Standing Waves Occur At Many More Frequencies And Vary In Strength. • Putting In Sustained Broadband Noise Will Result In Highly Unique And Complex Spectrum Of Resonated Frequencies: A Spectral Fingerprint Of The Physical Object! • Strong Survival Value In Discriminating How Strongly Each Frequency (Out Of A Broad Range Of Frequencies) Is Being Reinforced By An Object.

  16. Resonation & Perception • Our Ears Are Spectrum Analysers • Inner Ears Compare Strengths Of Different Frequencies Coming From A Single Object. • We Can Associate Sounds We Hear With Objects We See, Even When We Can’t See Them! • Our Ears Report To Our Brains, Which Is Not Aware Of Separate Frequencies, But Instead Perceives Timbre - An Overall Sound Quality.

  17. From William Vennard: Singing The Mechanism & The Technique

  18. From Ralph Appleman: The Science Of Vocal Pedagogy

  19. The Purpose of Hearing • Scout Out Our Environment (for Predators and Food) Beyond Our Line Of Sight. • What is out there?! • Is It Moving Closer Or Further Away?! • Where Is It?!

  20. How We Hear • What Is Out There? • Spectral analysis with either/both ears. (Previously explained)

  21. How We Hear • What Is Out There? • Spectral analysis with either/both ears. (Previously explained.) • Is It Moving Closer Or Further Away? • Changes in volume with either/both ears. (Inverse Square Law.)

  22. How We Hear • Where Is It? • Bianural Hearing: Comparing the same sound as heard by two physically separate, distinctly shaped ears: • Relative Loudness • Time Of Arrival • Head-Related Transfer Function

  23. How We Hear • Where Is It? • Two Separate Perceptions of Environmental Sound • Localization - I can point to the direction of the sound (e.g a lion’s roar) • Envelopment - I am inside the sound (e.g. rain & thunder)

  24. How We Localize Sound

  25. How We Localize Sound

  26. How We Localize Sound

  27. How We Localize Sound

  28. How We Localize Sound

  29. How We Localize Sound What’s The Difference? Head-Related Transfer Function

  30. Hi Fidelity/Home Theater Audio • To Simulate Nature It Must Reproduce • Realistic Complex Acoustic Spectrum • Accurate Full-Range Speakers • High-End Electronics • Realistic Volume Levels/Volume Changes • Sufficient Power and Speaker Sensitivity • Accurate, Clean Micro and Macro Dynamics • Realistic Binaural Cues via Multiple Speakers: • Relative Loudness • Time Of Arrival • Head-Related Transfer Function

  31. Hi Fidelity/Home Theater Audio • Monophonic Sound: • All sound sources sonically image at the speaker.

  32. Hi Fidelity/Home Theater Audio • 2-Channel Stereophonic Sound: • Sound sources sonically phantom-image between and behind the speakers. • Can have multiple simultaneous sonic phantom images. • Can smoothly pan a sonic phantom image. • 2 Discrete Channels

  33. Hi Fidelity/Home Theater Audio • Quadraphonic Sound • Sound sources sonically phantom-image between the front speakers, between the back speakers, but not between the side speakers. • 4 -> 2 Matrixed Channels and barely feasible Discrete

  34. Hi Fidelity/Home Theater Audio • Matrixed 4 Channels into 2 • 2 Channels – Lt & Rt provide: • Left Channel = Lt • Right Channel = Rt • Channel 3 = Lt + Rt • Channel 4 = Lt - Rt • Just 3 db Channel Isolation due to Inter-channel Bleeding. • Steering Logic Can Isolate Channels Further, But for Only One Phantom Image at a Time

  35. Hi Fidelity/Home Theater Audio • Dolby Stereo (Theaters) Thanks, Star Wars Episode 4 • Left/Center/Right Speakers Behind Screen + Single Surround Channel into Many Speakers for Envelopment • 4 -> 2 Matrixed Channels. Delayed, Frequency-Limited Surround Channel

  36. Hi Fidelity/Home Theater Audio • Dolby Pro Logic (Home) • Left/Center/Right w. Center Above/Below the Display + Single Surround Channel into 2 Dipolar Speakers for Envelopment • 4 -> 2 Matrixed Channels. Delayed, Frequency-Limited Surround Channel

  37. Hi Fidelity/Home Theater Audio • Digital 5.1 in Theaters • Left/Center/Right Speakers Behind Screen + Left Sur/Right Sur + Subwoofer • Discrete 5 Full-Range Channels + Discrete Subwoofer

  38. Hi Fidelity/Home Theater Audio • Digital 5.1 – Home Configuration • Left/Center/Right w. Center Above/Below the Display + Left Sur/Right Sur + Subwoofer -30o 0o +30o -120o +120o • Discrete 5 Full-Range Channels + Discrete Subwoofer

  39. Hi Fidelity/Home Theater Audio • Digital 6.1 in Theaters Thanks, Star Wars Episode 1 • Left/Center/Right Behind Screen + Left Sur/Back Sur/ Right Sur + Subwoofer • 5 Channels Discrete + Subwoofer + Back Channel Matrixed

  40. Hi Fidelity/Home Theater Audio • Digital 7.1 – Home Configuration • Left/Center/Right w. Center Above/Below the Display + Left Sur/Left Back/Right Back/Right Sur + Sub -30o 0o +30o -90o +90o -150o +150o • Discrete 7 Full-Range Channels + Discrete Subwoofer

  41. Digital Television

  42. Digital Television • It’s Coming February 17, 2009. Do you know where your programs are?

  43. Digital Television What Is It? • A Totally New Television System

  44. Digital Television What was wrong with the old Analog system?

  45. Digital Television What was wrong with the old Analog system? • 1930’s Technology

  46. Digital Television What was wrong with the old Analog system? • 1930’s Technology • Black & White

  47. Digital Television What was wrong with the old Analog system? • 1930’s Technology • Black & White • Monophonic Sound

  48. Digital Television What was wrong with the old Analog system? • 1930’s Technology • Black & White • Monophonic Sound • Maximum Screen Size: 19 inches

  49. Digital Television What was wrong with the old Analog system? • 1930’s Technology • Black & White • Monophonic Sound • Maximum Screen Size: 19 inches • Kluged Retrofits: Still not close to photographic and larger-than-life quality of movies.