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Essentials of AV Technology Audio Systems

Essentials of AV Technology Audio Systems. Part One Hearing and Sound. Hearing and Sound Introduction. Hearing and Sound Sound Waves Wavelength Frequency Octaves and Bands Harmonics. Hearing and Sound. The mechanics of human hearing. Outer ear Ear canal Ear drum Middle ear Cochlea.

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Essentials of AV Technology Audio Systems

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  1. Essentials of AV TechnologyAudio Systems

  2. Part OneHearing and Sound

  3. Hearing and Sound Introduction • Hearing and Sound • Sound Waves • Wavelength • Frequency • Octaves and Bands • Harmonics

  4. Hearing and Sound The mechanics of human hearing • Outer ear • Ear canal • Ear drum • Middle ear • Cochlea

  5. Sound Waves

  6. Wavelength Wavelength: Distance between two points that occur at the sample place.

  7. Frequency Frequency: Number of cycles completed in one second.

  8. Octaves and Bands Octave: Interval between a frequency and the doubling of that frequency

  9. Harmonics Harmonics: Whole number multiple of a fundamental frequency. Complex waveforms: Comprised of a fundamental frequency plus many harmonics.

  10. Human Perception of Sound Introduction • Human Perception of Sound Introduction • Logarithms • Decibels • Decibels Equations • Using the Decibel • Inverse Square Law and Sound

  11. Logarithms Number of times the number 10 must be multiplied by itself to get a desired value Logarithmic scales make ratios easier to express We perceive our world in a logarithmic way

  12. Decibels • Describes ratios with a wide range of values • Quantifies relationship between two numbers • In AV used for power, distance, voltage, and sound pressure

  13. Decibels Equations Power: dB = 10 * log (P1 / P2) Voltage: dB = 20 * log (V1 / V2) Distance: dB = 20 * log (D1 / D2)

  14. Using the Decibel

  15. Inverse Square Law and Sound • Energy inversely proportional to square of distance from source • 6 dB reduction is a doubling of distance • 6 dB gain is a halving of distance

  16. Part TwoAcoustics

  17. Acoustics • Acoustics • Sound Energy • Reflected Sound Energy • Reverberation • Absorption • Transmission • Ambient Noise

  18. Sound Energy Reflection: Energy sent back into a room Absorption: Energy absorbed into a medium Transmission: Energy passes through a medium

  19. Reflected Sound Energy Echo: Delays due to time and distance

  20. Reverberation Numerous persistent reflections Live environment High level energy Multiple reflections

  21. Absorption Porous Materials • Carpets • Acoustic tiles • Curtains • Clothing

  22. Transmission Energy passing through surfaces • Walls • Floors

  23. Ambient Noise Any sound other than the desired signal • Air conditioning • Equipment fans • Machines • Sound through windows

  24. Part ThreeCapturing Sound

  25. Microphone Types Introduction • Audio Signal Pathway • Dynamic Microphone • Condenser Microphone • Phantom Power • Electret Microphones • Microphone Physical Design and Placement

  26. Audio Signal Pathway Energy: Acoustic to electrical to acoustic

  27. Dynamic Microphone • Response of diaphragm to pressure • Movement induces voltage • No power source

  28. Condenser Microphone • Capacitor: Diaphragm and fixed back plate • Power Source • Electret Microphone • Size • Battery Option

  29. Phantom Power • Remote Power Source • Mixer • Outboard Supply • 12 - 48 volts DC

  30. Electret Microphones • Type of condenser mic • Named after prepolarized material applied to the diaphram or backplate • Requires less voltage than a typical condenser • Can be very small

  31. Microphone Physical Design and Placement Surface Mount Shotgun Handheld Gooseneck Lavalier

  32. Microphone Specifications Introduction • Microphone Polar Patterns • Microphone Sensitivity • Microphone Frequency Response • Microphone Impedance

  33. Microphone Polar Patterns Omnidirectional Cardioid Supercardioid Bi-directional • Hypercardioid: Variant of cardioid. • Directional, rejects sound from sides.

  34. Microphone Sensitivity • Output level referenced to input level • Condensers vs. dynamics

  35. Microphone Frequency Response Microphone Frequency Response: The range of frequencies a microphone can transduce.

  36. Microphone Impedance • Low impedance ( <200 ohms) • High impedance ( >25k ohms) 200 ohm mic level output 2000 ohm mic level input

  37. Microphone Signal Transport Introduction • Wireless Microphones • Microphone Cables and Connectors

  38. Wireless Microphones • Radio frequency transmission • Hands free

  39. Microphone Cables and Connectors • Shielded twisted pair cable • XLR male and XLR female

  40. Part FourAudio Signal Levels

  41. Audio Signal Levels Introduction • Audio Signal Levels • Signal Level Compatibility • Signal Level Adjustments

  42. Audio Signal Levels Microphone preamplifier boosts a mic level signal.

  43. Signal Level Compatibility • Inputs and signal level • Microphone input, mic level signal • Line level input, line level signal • Powered loudspeaker • Operating manual

  44. Signal Level Adjustments

  45. Part FiveAudio Components

  46. Audio Components Introduction • Audio Mixers • Audio Processors: Compressions, Limiters, and Expanders • Audio Processors: Gates and Filters • Equalizers • Delays • Power Amplifiers

  47. Audio Mixers • Multiple inputs to one or more outputs • Identifying mixer configurations

  48. Audio Processors: Compressions, Limiters, and Expanders • Processors: Control dynamic range with defined thresholds • Compressor: keeps loud signals from being too loud • Limiter: creates a ceiling to prevent signal spikes from damaging equipment • Expander: Reduced unwanted background noise

  49. Audio Processors: Impact on a Signal Audio Compressor:Impact on Signal Audio Limiter:Impact on Signal

  50. Audio Processors: Gates and Filters

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