Audio Signal

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					Audio Signal
          sound waves of
 compressed air molecules
                                 diaphragm
                                                 permanent magnet




                                                moving core
                                                              waves of electrical energy
                               coil

                                         Microphone

                         coil and core       magnet




     electrical signal
                                            diaphragm
                                                                   sound waves
                                          Speaker
Microphones

Mics are classified by either:
 their generating element (transducer)
   dynamic
   condenser (electret)
   ribbon (velocity)
 their pickup pattern
   omnidirectional
   cardioid or unidirectional
 Generating Elements -
 Transducers


                    output voltage
diaphragm                            polymer film diaphragm    impedance converter

                        spacer                                              output voltage
                  magnet
voice coil                  permanently charged
                                                    perforated back plate
                            electret coating
                magnetic
                structure



        Dynamic                        Condenser Microphone Element
   Microphone Element
Performance Characteristics of
Mic Transducers

 Dynamic mics
   durable, have good sound quality
 Condenser mics
   excellent sound (good frequency
    response), require a power source, are
    somewhat fragile
 Ribbon mics
   produce warm sound (excellent frequency
    response), are extremely fragile
Dynamic and Condenser Mic
Pros and Cons

Dynamic Mic Advantages            Condenser Mic Advantages
   Rugged                           More Sensitive
   Lower Cost                       Better Audio Quality
   No Power Required                Can Be Extremely Small


Dynamic Mic Disadvantages         Condenser Mic Disadvantages
   Lower Sensitivity and Power      Higher self-noise
    Output                           More Fragile
   Larger and Heavier               More Expensive
   Slower Response Time             Prone to Weather Problems and
   Not the Best Choice for           RF Interference
    Maximum Audio Quality
Omnidirectional
Pickup Pattern
Omnidirectional
Pickup Pattern
Cardioid Pickup Pattern
Cardioid Pickup Pattern
Hypercardioid Pickup Pattern
Connectors

      XLR connectors    phono plug




            RCA phone plug   mini plug
Audio Mixer

     Select and amplify the incoming sound
      signals.
     Control the volume of the various inputs.




     Mix or combine and balance two or more
      incoming sound signals.
Mixer Inputs

               Each input module
               requires that you select
               either the mic or line
               input.
Mixer Output/VU Meter

     The mixed and quality-
     processed signal is then
     routed to the output,
     sometimes called line-out.
Volume Unit (VU) Meters




         Analog VU Meters


 VU meters measure the
 volume units, the relative
 loudness of amplified
                              Digital VU Meters
 sound.
Calibration




An audio system is calibrated when all VU meters respond in the same
way to a specific audio signal—the control tone. Here the line-out of
the audio mixer is calibrated with the input (recording level) of the VTR.
Both VU meters show the same value.
Mixing Control—Analog Audio

                         Create proper
                          balance of sound.
                         Keep VU meter(s) in
                          range between 60-
                          100% (-5 to 0).
                         VU above 100%
                  100%    distorts
                         VU below 60%
                  60%     sounds weak and
                          may introduce noise
                          into the audio signal.
                         “Riding the gain”
                          means adjusting the
                          input faders to
                          maintain optimal
                          level and balance.
Digital Audio



       Display



                 Stereo
                 meters
    Calibration—Digital Audio
                                                                   Digital sound is
                                                                    especially
                                                                    susceptible to
                                                                    overmodulation.
                                                        Stereo      You should
                                                        meters      therefore set the
Display                                                             audio levels
                                                                    somewhat lower
                                                        Contrast    than for analog
                                                        control     sound.
                                                                   To calibrate our
                                                                    digital console
                                                                    feed a -12db tone.
    Left Tab                            Right Tab                   That is the optimal
    Scroll button   [F1]–[F4] buttons   Scroll button               level for Final Cut
                                                                    Pro.
   Mixing Control—Digital Audio
                                                              Digital sound is
                                                               especially
                                                               susceptible to
                                                               overmodulation. You
                                                               should therefore set
                                                     Stereo    the audio levels
                                                     meters
Display                                                        somewhat lower
                                                               than for analog
                                                               sound.
                                                     Contrast
                                                     control
                                                              Set the input faders
                                                               at a maximum of -15
                                                               to -12db rather than
                                                               0db.
                                                              “Riding the gain”
   Left Tab                            Right Tab               means adjusting the
   Scroll button   [F1]–[F4] buttons   Scroll button           input faders to
                                                               maintain optimal
                                                               level and balance.

				
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