Microphone Information Page
|Microphone Vendors||Microphone considerations:
Most speech recognition engine vendors recommend a that the application developer use the microphone specifed for the specific engine, and that the end user use an equivalent microphone. In choosing a microphone, care should be used since the choice of a microphone can influence speech recognition accuracy. An alternative microphone should be very high quality and designed for close range pickup to reduce background noise. The microphone must have a flat audio response range.
A typical microphone would have the following characteristics:
Type: Electret DC Input Voltage: 2.5 to 5 V DC Frequency response: 50 to 15,000 Hz Polar pattern: Bi-directional, with opposing lobes added with a 180 degree relative phase shift for noise cancellation Impedance: 2.2 Kohms (with 2.2 Kohm collector resistor) Output level: 20 mVp-p @ 2.5 V DC Input
40 mVp-p @ 5.0 V DC Input
(@ 104 dB SPL, 0.5 inches from sound source) Sensitivity: -63 +3 dB (0 dB = 1 V/ubar at 1 KHz)
Checking your microphone
If you don't do this, speech recognition might not work properly.