The Musical Videoconference Audio Quality vs. Echo Cancellation Dr. Brian K. Shepard Coordinator of Music Technology Programs University of Oklahoma School.

The Musical VideoconferenceThe Musical Videoconference

Audio QualityAudio Qualityvs.vs.

Echo CancellationEcho Cancellation

Dr. Brian K. ShepardDr. Brian K. ShepardCoordinator of Music Technology ProgramsCoordinator of Music Technology Programs

University of Oklahoma School of MusicUniversity of Oklahoma School of Music

Microphone TypesMicrophone Types

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

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

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

MicrophoneMicrophonePolar PatternsPolar Patterns

Omnidirectional MicrophoneOmnidirectional Microphone

The Omnidirectional Microphone hears in a 360º sphereThe Omnidirectional Microphone hears in a 360º spherearound the diaphragm.around the diaphragm.

DiaphragmDiaphragm

Figure-8 MicrophoneFigure-8 Microphone

The “Figure-8” or Bidirectional Microphone hears inThe “Figure-8” or Bidirectional Microphone hears infront of and behind the diaphragm.front of and behind the diaphragm.

Cardioid MicrophoneCardioid Microphone

The Cardioid Pattern Microphone hears predominantlyThe Cardioid Pattern Microphone hears predominantlyin front of the diaphragmin front of the diaphragm

Supercardioid MicrophoneSupercardioid Microphone

The Supercardioid Pattern Microphone hears mostly inThe Supercardioid Pattern Microphone hears mostly infront of the diaphragm, but has a small rear pickup lobe.front of the diaphragm, but has a small rear pickup lobe.

Hypercardioid MicrophoneHypercardioid Microphone

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

Boundary MicrophoneBoundary Microphone

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

PhysicalPhysicalEcho-CancellationEcho-Cancellation

Physical Echo-CancellationPhysical Echo-Cancellation

Dynamic, CardioidDynamic, CardioidPattern MicrophonesPattern Microphonesplaced close to theplaced close to the

performerperformer

Speakers positionedSpeakers positionedbehind, and off-axisbehind, and off-axisto the Microphonesto the Microphones

Non-Reflective Surface behind the PerformerNon-Reflective Surface behind the Performer

ElectronicElectronicGadgetsGadgets

Echo-CancellationEcho-CancellationModulesModules

Using Compression to “Duck”Using Compression to “Duck”Speaker LevelsSpeaker Levels

• Insert a “Sidechain” Compressor on Speaker Insert a “Sidechain” Compressor on Speaker ChannelsChannels

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

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

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

• Ratio: Try between 5:1 and 7:1Ratio: Try between 5:1 and 7:1• Attack: Try between 100 to 250 msAttack: Try between 100 to 250 ms• Release: Try between 500 to 1000 msRelease: Try between 500 to 1000 ms• Makeup Gain: Set at 0 dBMakeup Gain: Set at 0 dB

Compressor DetailCompressor Detail

Using Gates or Expanders to Using Gates or Expanders to Silence MicrophonesSilence Microphones

• Insert a Gate or Expander on each Microphone Insert a Gate or Expander on each Microphone ChannelChannel

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

Using Gates or Expanders to Using Gates or Expanders to Silence Microphones (cont.)Silence Microphones (cont.)

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

• Ratio (Expander): Set below 1:1, Try 0.5:1Ratio (Expander): Set below 1:1, Try 0.5:1• Attack: Try between 2 to 10 msAttack: Try between 2 to 10 ms• Release: Try between 50 to 200 msRelease: Try between 50 to 200 ms• Makeup Gain (Expander): Set at 0 dBMakeup Gain (Expander): Set at 0 dB

Gate DetailGate Detail

Expander DetailExpander Detail

Using a Limiter to ControlUsing a Limiter to ControlAudio Pops and “Hits”Audio Pops and “Hits”

• Insert a Compressor/Limiter on Speaker ChannelsInsert a Compressor/Limiter on Speaker Channels• Threshold: Set just above highest sound levelThreshold: Set just above highest sound level• Ratio: Set to 20:1 or greaterRatio: Set to 20:1 or greater• Attack: Set as short as possibleAttack: Set as short as possible• Makeup Gain: Set to 0Makeup Gain: Set to 0

Limiter DetailLimiter Detail

For More InformationFor More InformationDr. Brian K. ShepardDr. Brian K. Shepard

Coordinator of Music Technology ProgramsCoordinator of Music Technology Programs

OU School of MusicOU School of Music

500 West Boyd Street, Room 138500 West Boyd Street, Room 138

Norman, OK 73019Norman, OK 73019

(405) 325-0429(405) 325-0429

bkshepard@ou.edubkshepard@ou.edu

music.ou.edu/internet2music.ou.edu/internet2