by Bob Zurek
On May 19th Guy Torio of Shure Brothers Incorporated gave a presentation on understanding the transfer functions of directional condenser microphones. Guy began his talk by touching on how directional microphones work by detecting the pressure difference between two points. He went on to discuss how the delay in signal between the pickups determines the directional pattern of the microphone. Mr. Torio then showed how this delay is created with an acoustic resistance and cavity, and how these components form a low pass filter. He then showed how this system could be simulated using equivalent circuit analysis. Guy then proceeded to tell the audience how the proximity effect coupled with the more traditional analysis creates a system that has both high pass and low pass filter gains. The presentation then covered the directionality of the proximity effect through the use of simulations with different delays(d). Guy presented data that showed the frequency dependant effect of proximity due to angle of incidence and distance of the microphone from the source through frequency response curves and polar plots. The result of Mr. Torio's work shows that proximity has a bi-directional directivity effect that is independent of pass band directivity.
The section would like to extend its appreciation to Mr. Torio for taking the time to share his work with us at last month's meeting.
