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1 © 2012 InfoComm International Essentials of AV Technology Audio Systems
2 © 2012 InfoComm International Part One Hearing and Sound
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 © 2012 InfoComm International Hearing and Sound The mechanics of human hearing Outer ear Ear canal Ear drum Middle ear Cochlea
5 © 2012 InfoComm International Sound Waves Created by two events Compression Rarefaction
6 © 2012 InfoComm International Wavelength Wavelength: Distance between two points that occur at the sample place.
7 © 2012 InfoComm International Frequency Frequency: Number of cycles completed in one second.
8 © 2012 InfoComm International Octaves and Bands Octave: Interval between a frequency and the doubling of that frequency
9 © 2012 InfoComm International Harmonics Harmonics: Whole number multiple of a fundamental frequency. Complex waveforms: Comprised of a fundamental frequency plus many harmonics.
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 © 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 © 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 © 2012 InfoComm International Decibels Equations Power: dB = 10 * log (P1 / P2) Voltage: dB = 20 * log (V1 / V2) Distance: dB = 20 * log (D1 / D2)
14 © 2012 InfoComm International Using the Decibel Common References:
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 © 2012 InfoComm International Part Two Acoustics
17 © 2012 InfoComm International Acoustics 1.Acoustics 2.Sound Energy 3.Reflected Sound Energy 4.Reverberation 5.Absorption 6.Transmission 7.Ambient Noise
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 © 2012 InfoComm International Reflected Sound Energy Types of reflection Direct (specular) Scattered (diffuse) Echo: Delays due to time and distance
20 © 2012 InfoComm International Reverberation Numerous persistent reflections Live environment High level energy Multiple reflections
21 © 2012 InfoComm International Absorption Porous Materials Carpets Acoustic tiles Curtains Clothing
22 © 2012 InfoComm International Transmission Energy passing through surfaces Walls Floors
23 © 2012 InfoComm International Ambient Noise Any sound other than the desired signal Air conditioning Equipment fans Machines Sound through windows
24 © 2012 InfoComm International Part Three Capturing Sound
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 © 2012 InfoComm International Audio Signal Pathway Energy: Acoustic to electrical to acoustic
27 © 2012 InfoComm International Dynamic Microphone Response of diaphragm to pressure Movement induces voltage No power source
28 © 2012 InfoComm International Condenser Microphone Capacitor: Diaphragm and fixed back plate Power Source Electret Microphone Size Battery Option
29 © 2012 InfoComm International Phantom Power Remote Power Source Mixer Outboard Supply volts DC
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 © 2012 InfoComm International Microphone Physical Design and Placement Handheld Surface Mount Gooseneck Shotgun Lavalier
32 © 2012 InfoComm International Microphone Specifications Introduction 1.Microphone Polar Patterns 2.Microphone Sensitivity 3.Microphone Frequency Response 4.Microphone Impedance
33 © 2012 InfoComm International Microphone Polar Patterns Hypercardioid: Variant of cardioid. Directional, rejects sound from sides. OmnidirectionalCardioidSupercardioidBi-directional
34 © 2012 InfoComm International Microphone Sensitivity Output level referenced to input level Condensers vs. dynamics
35 © 2012 InfoComm International Microphone Frequency Response Microphone Frequency Response: The range of frequencies a microphone can transduce.
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 © 2012 InfoComm International Microphone Signal Transport Introduction 1.Wireless Microphones 2.Microphone Cables and Connectors
38 © 2012 InfoComm International Wireless Microphones Radio frequency transmission Hands free
39 © 2012 InfoComm International Microphone Cables and Connectors Shielded twisted pair cable XLR male and XLR female
40 © 2012 InfoComm International Part Four Audio Signal Levels
41 © 2012 InfoComm International Audio Signal Levels Introduction 1.Audio Signal Levels 2.Signal Level Compatibility 3.Signal Level Adjustments
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 © 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 © 2012 InfoComm International Signal Level Adjustments Signal adjustments = Amplitude adjustments o Unity (no change) o Gain (increase) Attenuation (decrease)
45 © 2012 InfoComm International Part Five Audio Components
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 © 2012 InfoComm International Audio Mixers Multiple inputs to one or more outputs Identifying mixer configurations
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 © 2012 InfoComm International Audio Processors: Impact on a Signal Audio Limiter: Impact on Signal Audio Compressor: Impact on Signal
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 © 2012 InfoComm International Equalizers Graphic 1/3 Octave Parametric Complex frequency management Frequency response management
52 © 2012 InfoComm International Delays Delay: Compensation for distance and location
53 © 2012 InfoComm International Power Amplifiers Amplifiers: boost the signal with enough energy to move the loudspeaker.
54 © 2012 InfoComm International Part Five Loudspeakers
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 © 2012 InfoComm International Loudspeakers Introduction Audio Signal Chain Electrical energy to acoustic energy General applications Communication Reinforcement Reproduction
57 © 2012 InfoComm International Crossovers Divide frequencies into specific ranges Different drivers for different frequencies Tweeters Horns Woofer Subwoofer
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 © 2012 InfoComm International Loudspeaker Frequency Response and Polar Patterns Dispersions at different frequencies Listener position Polar plots map performance
60 © 2012 InfoComm International Loudspeaker Impedance Matching amplifiers and loudspeakers Common impedances o4, 8,16 ohms
61 © 2012 InfoComm International Center Cluster and Distributed Systems Center cluster oFocus on presentation area Distributed systems oOrigin of sound not important
62 © 2012 InfoComm International Part Six Audio Signal Level Monitoring
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 © 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 © 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 © 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 © 2012 InfoComm International Balanced and Unbalanced Circuits Balanced o Combats noise Unbalanced o Susceptible to noise
68 © 2012 InfoComm International Balanced and Unbalanced Distinctions Number of conductors and circuit type
69 © 2012 InfoComm International Feedback Feedback Definition Loudspeaker placement
70 © 2012 InfoComm International Part Seven Audio System Applications
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 © 2012 InfoComm International Sound Reinforcement Sound amplification oMusic reinforcement oSpeech reinforcement
73 © 2012 InfoComm International Mix-Minus Systems Mix-minus system characteristics oMultiple subsystems (zones)
74 © 2012 InfoComm International Playback and Combination Systems Playback system Reinforce recorded material No microphone sources Combination system Single system supporting multiple purposes
75 © 2012 InfoComm International Audio Conferencing and Videoconferencing Audio conferencing o Communicate with groups Videoconferencing o Supporting system
76 © 2012 InfoComm International Sound Masking Systems Minimize transmission Create intelligibility Provide sense of privacy Noise systems
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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