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Microphones, Speakers and Echo Cancellation. Dr. Brian K. Shepard Coordinator of Music Technology Programs University of Oklahoma School of Music. Microphone Types. Dynamic - rugged, warm sounding, requires higher sound levels

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Microphones speakers and echo cancellation l.jpg

Microphones, Speakersand Echo Cancellation

Dr. Brian K. Shepard

Coordinator of Music Technology Programs

University of Oklahoma School of Music


Microphone types l.jpg
Microphone Types

  • Dynamic - rugged, warm sounding, requires higher sound levels

  • Ribbon - rather fragile, warm sounding, works with fairly low sound levels

  • Condenser - fairly sturdy, bright and crisp sounding (accurate), will work with extremely low sound levels


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MicrophonePolar Patterns


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Omnidirectional Microphone

Diaphragm

The Omnidirectional Microphone hears in a 360º sphere

around the diaphragm.


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Figure-8 Microphone

The “Figure-8” or Bidirectional Microphone hears in

front of and behind the diaphragm.


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Cardioid Microphone

The Cardioid Pattern Microphone hears predominantly

in front of the diaphragm


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Supercardioid Microphone

The Supercardioid Pattern Microphone hears mostly in

front of the diaphragm, but has a small rear pickup lobe.


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Hypercardioid Microphone

The Hypercardioid Pattern Microphone hears mostly in front of the diaphragm, but with a larger rear lobe and very little side pickup.


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Boundary Microphone

Because the Boundary Microphone is placed on a flat surface, it hears above and beside the diaphragm in a half-spherical pattern.


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PhysicalEcho-Cancellation


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Physical Echo-Cancellation

Non-Reflective Surface behind the Performer

Speakers positioned

behind, and off-axis

to the Microphones

Dynamic, Cardioid

Pattern Microphones

placed close to the

performer


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ElectronicGadgets



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Using Compression to “Duck”Speaker Levels

  • Insert a “Sidechain” Compressor on Speaker Channels

  • Set Sidechain “Key” input to the signal from the local microphone(s)


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Using Compression to “Duck”Speaker Levels (cont.)

  • Threshold: Set so the local person’s level is above the threshold, while the remote level is below.

  • Ratio: Try between 5:1 and 7:1

  • Attack: Try between 100 to 250 ms

  • Release: Try between 500 to 1000 ms

  • Makeup Gain: Set at 0 dB



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Using Gates or Expanders to Silence Microphones

  • Insert a Gate or Expander on each Microphone Channel

  • Gates turn off the channel, while Expanders turn down the channel. Thus, Expanders are usually more graceful than Gates.


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Using Gates or Expanders to Silence Microphones (cont.)

  • Threshold: Set so that the local person’s softest level is above the threshold.

  • Ratio (Expander): Set below 1:1, Try 0.5:1

  • Attack: Try between 2 to 10 ms

  • Release: Try between 50 to 200 ms

  • Makeup Gain (Expander): Set at 0 dB




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For More Information

Dr. Brian K. Shepard

Coordinator of Music Technology Programs

OU School of Music

500 West Boyd Street, Room 138

Norman, OK 73019

(405) 325-0429

bkshepard@ou.edu

music.ou.edu/internet2


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