1. Microphones, Speakers and Echo Cancellation
Dr. Brian K. Shepard
Coordinator of Music Technology Programs
University of Oklahoma School of Music

2. 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

3. Microphone Polar Patterns

4. Omnidirectional Microphone
Diaphragm
The Omnidirectional Microphone hears in a 360º sphere
around the diaphragm.

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

6. Cardioid Microphone
The Cardioid Pattern Microphone hears predominantly
in front of the diaphragm

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

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

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

10. Physical Echo-Cancellation

11. Physical Echo-Cancellation
Speakers positioned
behind, and off-axis
to the Microphones
Dynamic, Cardioid
Pattern Microphones
placed close to the
performer
Non-Reflective Surface behind the Performer

12. Electronic Gadgets

13. Echo-Cancellation Modules

14. 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)

15. 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

16. Compressor Detail

17. 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.

18. 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

19. Gate Detail

20. Expander Detail

21. Coordinator of Music Technology Programs
For More Information
Dr. Brian K. Shepard
Coordinator of Music Technology Programs
OU School of Music
500 West Boyd Street, Room 138
Norman, OK
(405)
music.ou.edu/internet2