Optimizing AudioOptimizing Audiofor thefor the

The Musical VideoconferenceThe Musical Videoconference

Brian K. ShepardBrian K. ShepardChair, Department of Music TechnologyChair, Department of Music Technology

University of Oklahoma School of MusicUniversity of Oklahoma School of Music

The Three Secrets ofThe Three Secrets ofAudio SuccessAudio Success

• LocationLocation

• LocationLocation

• LocationLocation

of musician(s) inside the roomof musician(s) inside the room

of proper microphones in relation to the musician(s)of proper microphones in relation to the musician(s)

of microphones in relation to the loudspeakersof microphones in relation to the loudspeakers

Microphone TypesMicrophone Types

• Dynamic - Dynamic - rugged, warm sounding, requires rugged, warm sounding, requires higher sound levels, higher sound levels, good echo rejectiongood echo rejection

• Ribbon - Ribbon - rather fragile, warm sounding, works with rather fragile, warm sounding, works with fairly low sound levels, fairly low sound levels, moderate echo rejectionmoderate echo rejection

• 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 levels, sound levels, poor echo rejectionpoor echo rejection

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 in frontThe Supercardioid Pattern Microphone hears mostly in frontof the diaphragm, a little less to the side, and a smallof the diaphragm, a little less to the side, and a small

pickup area to the rear.pickup area to the rear.

Hypercardioid MicrophoneHypercardioid Microphone

The Hypercardioid Pattern Microphone hears mostly inThe Hypercardioid Pattern Microphone hears mostly infront of the diaphragm, with very little side pickup and afront of the diaphragm, with very little side pickup and a

slightly larger pickup pattern to the rear.slightly larger pickup pattern to the rear.

Boundary MicrophoneBoundary Microphone

The Boundary Microphone is placed on a flat surface.The Boundary Microphone is placed on a flat surface.Thus, it hears above and beside the diaphragm in aThus, it hears above and beside the diaphragm in a

half-spherical pattern.half-spherical pattern.

PhysicalPhysicalEcho RejectionEcho Rejection

Physical Echo RejectionPhysical Echo Rejection

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

performerperformer

Speakers positionedSpeakers positionedbehind, or off-axisbehind, or off-axis

to the Microphonesto the Microphones

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

ElectronicElectronicGadgetsGadgets

OnlyOnly after completing all the after completing all the Physical Echo Rejection Physical Echo Rejection

TechniquesTechniques

Echo-CancellationEcho-CancellationModulesModules

Using Compression to “Duck”Using Compression to “Duck”Local Speaker LevelsLocal Speaker Levels

• Helps reduce the echo at Helps reduce the echo at youryour (local) end (local) end• 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”Local Speaker LevelsLocal Speaker Levels

• 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 10:1 and 15:1Ratio: Try between 10:1 and 15:1• 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 TipsCompressor Tips• If speakers are constantly “ducked,” raise the If speakers are constantly “ducked,” raise the

threshold. Set the threshold so that when you are threshold. Set the threshold so that when you are speaking or playing, the speakers are “ducked,” but speaking or playing, the speakers are “ducked,” but when the remote end is speaking or playing, the when the remote end is speaking or playing, the speakers are at full level.speakers are at full level.

• Increase the ratio to make the speakers drop lower in Increase the ratio to make the speakers drop lower in level when you speak or play. If they drop too much, level when you speak or play. If they drop too much, lower the ratio.lower the ratio.

• The attack time should be just shorter than the round The attack time should be just shorter than the round trip echo time (generally between 100-250 ms).trip echo time (generally between 100-250 ms).

• Too short of a release time can cause the Too short of a release time can cause the compressor to “pump.” Keep the release time in the compressor to “pump.” Keep the release time in the 500-1000 ms range.500-1000 ms range.

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

• Helps reduce the echo at the Helps reduce the echo at the remoteremote end end• Insert a Gate or Expander on each Microphone Insert a Gate or Expander on each Microphone

ChannelChannel• Gates turn off the channel when the input level drops, Gates turn off the channel when the input level drops,

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

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

• 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 1 to 10 msAttack: Try between 1 to 10 ms• Release: Try around 200 msRelease: Try around 200 ms• Makeup Gain (Expander): Set at 0 dBMakeup Gain (Expander): Set at 0 dB

Gate and Expander TipsGate and Expander Tips• If the audio from the remote end opens the gate or If the audio from the remote end opens the gate or

the expander, raise the threshold. Set the threshold the expander, raise the threshold. Set the threshold so that the gate or expander opens when you talk or so that the gate or expander opens when you talk or play, but remains closed when the remote person play, but remains closed when the remote person talks or plays.talks or plays.

• Set the attack time as fast as possible so that the Set the attack time as fast as possible so that the beginnings of your sounds do not get clipped off.beginnings of your sounds do not get clipped off.

• Set the release (or hold and release) time so that Set the release (or hold and release) time so that your sounds can taper off naturally before the gate or your sounds can taper off naturally before the gate or expander closes (usually 200 ms or so).expander closes (usually 200 ms or so).

• If your gate has a “range” value, experiment with If your gate has a “range” value, experiment with settings near the midpoint. This will cause the gate settings near the midpoint. This will cause the gate to act more like an expander by dropping the audio to act more like an expander by dropping the audio level rather than cutting it completely.level rather than cutting it completely.

General Tips for Best ResultsGeneral Tips for Best Results

• Do physical Echo Rejection first!Do physical Echo Rejection first!

• Remember, do physical Echo Rejection first!Remember, do physical Echo Rejection first!

• Do a little compression and gating at each Do a little compression and gating at each end rather than a lot at just one end.end rather than a lot at just one end.

• Did I mention that you should do physical Did I mention that you should do physical Echo Rejection first?Echo Rejection first?

Mixer and Cabling TipsMixer and Cabling Tips• Use a mixer that allows Auxiliary Sends to be set to Use a mixer that allows Auxiliary Sends to be set to

“Pre-Fader,” or has assignable Bus outputs.“Pre-Fader,” or has assignable Bus outputs.

• Connect your microphones to separate mixer input Connect your microphones to separate mixer input channels. Assign the microphone channels to either channels. Assign the microphone channels to either Auxiliary (pre-fader) outputs or to separate Bus Auxiliary (pre-fader) outputs or to separate Bus outputs, but not to the Master L/R mix. Connect the outputs, but not to the Master L/R mix. Connect the Auxiliary outputs (or Bus outputs) to the audio inputs Auxiliary outputs (or Bus outputs) to the audio inputs of the codec.of the codec.

• Connect your codec’s audio outputs to two additional Connect your codec’s audio outputs to two additional mixer channel inputs and assign them to the Master mixer channel inputs and assign them to the Master L/R mix.L/R mix.

• Plug a Gate or Expander into each of the Microphone Plug a Gate or Expander into each of the Microphone channels via the “Insert” jack.channels via the “Insert” jack.

Mixer and Cabling TipsMixer and Cabling Tips• Plug a Compressor into each of your mixer’s Main Plug a Compressor into each of your mixer’s Main

output channels via the “Master Insert” jack.output channels via the “Master Insert” jack.

• Assign your Microphone channels to an additional Assign your Microphone channels to an additional (separate from the ones connected to the codec) (separate from the ones connected to the codec) Auxiliary output and connect that output to the Auxiliary output and connect that output to the Sidechain or “Key” input of the Compressor.Sidechain or “Key” input of the Compressor.

• Connect your mixer’s Main outputs to your amplifier Connect your mixer’s Main outputs to your amplifier and speakers.and speakers.

• If your mixer does not have a “Master Insert” jack, If your mixer does not have a “Master Insert” jack, plug the Main output into the Compressor’s input and plug the Main output into the Compressor’s input and connect the output of your Compressor to your connect the output of your Compressor to your amplifier and speakers.amplifier and speakers.

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

Chair, Department of Music TechnologyChair, Department of Music Technology

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.edumusic.ou.edu