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1 © 2012 InfoComm International Essentials of AV Technology Audio Systems.

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Presentation on theme: "1 © 2012 InfoComm International Essentials of AV Technology Audio Systems."— Presentation transcript:

1 1 © 2012 InfoComm International Essentials of AV Technology Audio Systems

2 2 © 2012 InfoComm International Part One Hearing and Sound

3 3 © 2012 InfoComm International Hearing and Sound Introduction 1.Hearing and Sound 2.Sound Waves 3.Wavelength 4.Frequency 5.Octaves and Bands 6.Harmonics

4 4 © 2012 InfoComm International Hearing and Sound The mechanics of human hearing  Outer ear  Ear canal  Ear drum  Middle ear  Cochlea

5 5 © 2012 InfoComm International Sound Waves Created by two events  Compression  Rarefaction

6 6 © 2012 InfoComm International Wavelength Wavelength: Distance between two points that occur at the sample place.

7 7 © 2012 InfoComm International Frequency Frequency: Number of cycles completed in one second.

8 8 © 2012 InfoComm International Octaves and Bands Octave: Interval between a frequency and the doubling of that frequency

9 9 © 2012 InfoComm International Harmonics Harmonics: Whole number multiple of a fundamental frequency. Complex waveforms: Comprised of a fundamental frequency plus many harmonics.

10 10 © 2012 InfoComm International Human Perception of Sound Introduction 1.Human Perception of Sound Introduction 2.Logarithms 3.Decibels 4.Decibels Equations 5.Using the Decibel 6.Inverse Square Law and Sound

11 11 © 2012 InfoComm International 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 12 © 2012 InfoComm International 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 13 © 2012 InfoComm International Decibels Equations Power: dB = 10 * log (P1 / P2) Voltage: dB = 20 * log (V1 / V2) Distance: dB = 20 * log (D1 / D2)

14 14 © 2012 InfoComm International Using the Decibel Common References:

15 15 © 2012 InfoComm International 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 16 © 2012 InfoComm International Part Two Acoustics

17 17 © 2012 InfoComm International Acoustics 1.Acoustics 2.Sound Energy 3.Reflected Sound Energy 4.Reverberation 5.Absorption 6.Transmission 7.Ambient Noise

18 18 © 2012 InfoComm International Sound Energy Reflection: Energy sent back into a room Absorption: Energy absorbed into a medium Transmission: Energy passes through a medium

19 19 © 2012 InfoComm International Reflected Sound Energy Types of reflection  Direct (specular)  Scattered (diffuse) Echo: Delays due to time and distance

20 20 © 2012 InfoComm International Reverberation Numerous persistent reflections Live environment High level energy Multiple reflections

21 21 © 2012 InfoComm International Absorption Porous Materials  Carpets  Acoustic tiles  Curtains  Clothing

22 22 © 2012 InfoComm International Transmission Energy passing through surfaces  Walls  Floors

23 23 © 2012 InfoComm International Ambient Noise Any sound other than the desired signal  Air conditioning  Equipment fans  Machines  Sound through windows

24 24 © 2012 InfoComm International Part Three Capturing Sound

25 25 © 2012 InfoComm International Microphone Types Introduction 1.Audio Signal Pathway 2.Dynamic Microphone 3.Condenser Microphone 4.Phantom Power 5.Electret Microphones 6.Microphone Physical Design and Placement

26 26 © 2012 InfoComm International Audio Signal Pathway Energy: Acoustic to electrical to acoustic

27 27 © 2012 InfoComm International Dynamic Microphone Response of diaphragm to pressure Movement induces voltage No power source

28 28 © 2012 InfoComm International Condenser Microphone Capacitor: Diaphragm and fixed back plate Power Source Electret Microphone Size Battery Option

29 29 © 2012 InfoComm International Phantom Power Remote Power Source Mixer Outboard Supply volts DC

30 30 © 2012 InfoComm International 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 31 © 2012 InfoComm International Microphone Physical Design and Placement Handheld Surface Mount Gooseneck Shotgun Lavalier

32 32 © 2012 InfoComm International Microphone Specifications Introduction 1.Microphone Polar Patterns 2.Microphone Sensitivity 3.Microphone Frequency Response 4.Microphone Impedance

33 33 © 2012 InfoComm International Microphone Polar Patterns Hypercardioid: Variant of cardioid. Directional, rejects sound from sides. OmnidirectionalCardioidSupercardioidBi-directional

34 34 © 2012 InfoComm International Microphone Sensitivity  Output level referenced to input level  Condensers vs. dynamics

35 35 © 2012 InfoComm International Microphone Frequency Response Microphone Frequency Response: The range of frequencies a microphone can transduce.

36 36 © 2012 InfoComm International Microphone Impedance  Low impedance ( <200 ohms)  High impedance ( >25k ohms) 200 ohm mic level output 2000 ohm mic level input

37 37 © 2012 InfoComm International Microphone Signal Transport Introduction 1.Wireless Microphones 2.Microphone Cables and Connectors

38 38 © 2012 InfoComm International Wireless Microphones  Radio frequency transmission  Hands free

39 39 © 2012 InfoComm International Microphone Cables and Connectors  Shielded twisted pair cable  XLR male and XLR female

40 40 © 2012 InfoComm International Part Four Audio Signal Levels

41 41 © 2012 InfoComm International Audio Signal Levels Introduction 1.Audio Signal Levels 2.Signal Level Compatibility 3.Signal Level Adjustments

42 42 © 2012 InfoComm International Audio Signal Levels DescriptionVoltage Level Mic Level0.001 volts Line Level (Professional)1 volt Line Level (consumer)0.316 volts Loudspeaker Level2 < 100 volts Microphone preamplifier boosts a mic level signal.

43 43 © 2012 InfoComm International Signal Level Compatibility  Inputs and signal level oMicrophone input, mic level signal oLine level input, line level signal  Powered loudspeaker  Operating manual

44 44 © 2012 InfoComm International Signal Level Adjustments  Signal adjustments = Amplitude adjustments o Unity (no change) o Gain (increase)  Attenuation (decrease)

45 45 © 2012 InfoComm International Part Five Audio Components

46 46 © 2012 InfoComm International Audio Components Introduction 1.Audio Mixers 2.Audio Processors: Compressions, Limiters, and Expanders 3.Audio Processors: Gates and Filters 4.Equalizers 5.Delays 6.Power Amplifiers

47 47 © 2012 InfoComm International Audio Mixers  Multiple inputs to one or more outputs  Identifying mixer configurations

48 48 © 2012 InfoComm International 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 49 © 2012 InfoComm International Audio Processors: Impact on a Signal Audio Limiter: Impact on Signal Audio Compressor: Impact on Signal

50 50 © 2012 InfoComm International Audio Processors: Gates and Filters ProcessorDescription GateMutes all signals below an adjustable threshold. FilterRegulates the passing of frequencies from a signal.

51 51 © 2012 InfoComm International Equalizers Graphic 1/3 Octave Parametric Complex frequency management Frequency response management

52 52 © 2012 InfoComm International Delays Delay: Compensation for distance and location

53 53 © 2012 InfoComm International Power Amplifiers Amplifiers: boost the signal with enough energy to move the loudspeaker.

54 54 © 2012 InfoComm International Part Five Loudspeakers

55 55 © 2012 InfoComm International Loudspeakers Intro 1.Loudspeakers Introduction 2.Loudspeakers 3.Crossovers 4.Loudspeaker Sensitivity 5.Loudspeaker Frequency Response and Polar Patterns 6.Loudspeaker Impedance 7.Center Cluster and Distributed Systems

56 56 © 2012 InfoComm International Loudspeakers Introduction Audio Signal Chain Electrical energy to acoustic energy General applications Communication Reinforcement Reproduction

57 57 © 2012 InfoComm International Crossovers  Divide frequencies into specific ranges  Different drivers for different frequencies  Tweeters  Horns  Woofer  Subwoofer

58 58 © 2012 InfoComm International Loudspeaker Sensitivity Loudspeaker Sensitivity Specifications Loudspeaker Performance Measurement: 88 1m This loudspeaker will deliver 88 decibels of sound pressure when receiving 1 watt of power measured at a distance of 1 meter.

59 59 © 2012 InfoComm International Loudspeaker Frequency Response and Polar Patterns Dispersions at different frequencies Listener position Polar plots map performance

60 60 © 2012 InfoComm International Loudspeaker Impedance  Matching amplifiers and loudspeakers  Common impedances o4, 8,16 ohms

61 61 © 2012 InfoComm International Center Cluster and Distributed Systems  Center cluster oFocus on presentation area  Distributed systems oOrigin of sound not important

62 62 © 2012 InfoComm International Part Six Audio Signal Level Monitoring

63 63 © 2012 InfoComm International Audio Signal Level Monitoring Introduction 1.Audio Signal Level Monitoring Introduction 2.Check Signal Levels 3.Audio Signal Level Monitoring 4.Signal Levels 5.Balanced and Unbalanced Circuits 6.Balanced and Unbalanced Distinctions 7.Feedback

64 64 © 2012 InfoComm International Check Signal Levels  Verify signals at all used mixer inputs.  Adjust gain levels wherever appropriate.  Turn on the power amplifier.  Slowly increase sound pressure to desired level.  Listen for distortion and correct as needed.

65 65 © 2012 InfoComm International Audio Signal Level Monitoring A PPM (Peak Program Meter) shows instantaneous peak levels and is very useful for digital recording. Volume Unit Indicator (VU)Peak Program Meter (PPM)

66 66 © 2012 InfoComm International Signal Levels Analog Signal Levels: 0 dBu or more Digital Signal Levels: can never exceed 0 dBu Signal is distorted if exceeded

67 67 © 2012 InfoComm International Balanced and Unbalanced Circuits  Balanced o Combats noise  Unbalanced o Susceptible to noise

68 68 © 2012 InfoComm International Balanced and Unbalanced Distinctions Number of conductors and circuit type

69 69 © 2012 InfoComm International Feedback  Feedback Definition  Loudspeaker placement

70 70 © 2012 InfoComm International Part Seven Audio System Applications

71 71 © 2012 InfoComm International Audio System Applications Introduction 1.Audio System Applications Introduction 2.Sound Reinforcement 3.Mix-Minus Systems 4.Playback and Combination Systems 5.Intercom and Paging Systems 6.Audio Conferencing and Videoconferencing 7.Sound Masking Systems 8.Audio Systems Summary

72 72 © 2012 InfoComm International Sound Reinforcement  Sound amplification oMusic reinforcement oSpeech reinforcement

73 73 © 2012 InfoComm International Mix-Minus Systems  Mix-minus system characteristics oMultiple subsystems (zones)

74 74 © 2012 InfoComm International Playback and Combination Systems  Playback system  Reinforce recorded material  No microphone sources  Combination system  Single system supporting multiple purposes

75 75 © 2012 InfoComm International Audio Conferencing and Videoconferencing  Audio conferencing o Communicate with groups  Videoconferencing o Supporting system

76 76 © 2012 InfoComm International Sound Masking Systems  Minimize transmission  Create intelligibility  Provide sense of privacy  Noise systems

77 77 © 2012 InfoComm International Audio Systems Summary  Sound Reinforcement  Mix-Minus  Playback and Combination Systems  Intercom and Paging Systems  Audio Conferencing and Audio for Videoconferencing  Sound Masking Systems


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