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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