-- RavichanderVipperla - 10 May 2010


Components

1) Spherical microphone array with 32 microphones (EM32). Each microphone has programmable preamplifiers and A/D Convertors embedded in the spherical baffle.

2) EigenMike Microphone Interface Box (EMIB) - converts the serial EM32 data to firewire interface.

3) Macbook: Integrated firewire interface with ASIO (Audio Stream Input Output) drivers installed. The laptop has a Sound editing/mixing software called Podium (from Zynewave) which has a VST plugin to take the 32 channel input and create 8 differently configured beamformed outputs.


Notes

  1. In the documentation of Eigenmike, it says that headphone volume control knob when in leftmost position gives highest volume. But rightmost position gives the highest volume.
  2. The EigenMike preamplifier has been set 10 dB. (Using C:\EM32 EigenMike>em32SetGain.exe 10)


Issues

  1. ASIO audio driver has an issue with 802.11 wireless interface. Hence the wireless ethernet needs to be disabled on the Mac when using the EigenMike. To check: Ethernet access points in Inspace.

Directional Patterns

Using the VST plugin for the EigeMike , the i/ps from the 32 microphones can be used to beamform in a certain direction and using a set of predefined directional patterns. There are eight output channels from the VST plugin and each can be configured independently.

To beamform in the direction of the source, one needs to manipulate 2 parameters, azimuth and elevation.

Azimuth: This is the angle in the horizontal direction ranging from 0-360 degrees. For the eigenMike, zero degrees corresponds to the direction of the blue button. The angle increases in anticlockwise direction looking from top. If you are facing the EigemMike such that the 'supporting stand' is farthest from you, then 0 degrees is to the right, 90 degrees is in the direction of supporting stand, 180 is to the left and 270 is the direction facing you.

Elevation: This is the angle in vertical direction ranging from 0-180 degrees. Zero degree corresponds to the top (where led is placed), 90 degrees is around the equator for the sphere and 180 is the bottom.

The following beam-form patterns are supported

  1. First order Cardioid
  2. Second order Cardioid
  3. Third order Cardioid
  4. First order Super-Cardioid
  5. Second order Super-Cardioid
  6. Third order Super-Cardioid
  7. First order Dipole
  8. Torus
  9. Omni

Topic revision: r4 - 16 Jun 2010 - 16:08:20 - RavichanderVipperla
 
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