# Essentials of AV Technology Audio Systems - PowerPoint PPT Presentation

Essentials of AV Technology Audio Systems

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Essentials of AV Technology Audio Systems

## Essentials of AV Technology Audio Systems

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##### Presentation Transcript

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