Use two standard electret microphone elements (Radio Shack part number 270-020C) to cancel out background noise.  Strong signals close to the microphone elements are easily passed, while the lower power background noise is canceled out.

See the December 2000 issue of QST magazine, pages 38-39, for more information and construction notes.

Schematics

• Noise Canceling Electret Microphone  (40k PNG)

Notes

• Dual-Microphones Separate Voice from Noise  EDN Design Ideas: June 23, 1994
• Noise Canceling with Electret Condenser Microphones  (134k PDF)