Data Sheet
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12 EasyVR 3 User Manual (1.0.11)
Examples
1) The optimal gain resistance for the bundled microphone at ARMS_LENGTH distance is:
Use the closest standard 5% resistor to Rs. In this example, it would be 1.1 kΩ. The EasyVR uses a 1.2 kΩ
resistor to allow use of “FAR” settings without replacing the internal resistor.
Sometimes you might also need to compensate some gain loss for a voltage lower than the microphone
ratings (using a larger resistor value sets a higher input gain).
2) The gain resistance for the bundled microphone at HEADSET distance would be:
In this case you may just add an external 1.2 kΩ resistor to get a gain resistance of 600 Ω (close enough).
Positioning guidelines
Please note that improper acoustic positioning of the microphone will reduce recognition accuracy. Many
mechanical arrangements are possible for the microphone element, and some will work better than others.
When mounting the microphone in the final device, keep in mind the following guidelines:
1. Flush Mounting - The microphone element should be positioned as close to the mounting surface
as possible and should be fully seated in the plastic housing. There must be no airspace between
the microphone element and the housing. Having such airspace can lead to acoustic resonance,
which can reduce recognition accuracy.
2. No Obstructions, Large Hole - The area in front of the microphone element must be kept clear of
obstructions to avoid interference with recognition. The diameter of the hole in the housing in front of
the microphone should be at least 5 mm. Any necessary plastic surface in front of the microphone
should be as thin as possible, being no more than 0.7 mm, if possible.
3. Insulation - The microphone should be acoustically isolated from the housing if possible. This can
be accomplished by surrounding the microphone element with a spongy material such as rubber or
foam. The provided microphone has this kind of insulating foam. The purpose is to prevent auditory
GOOD
BAD
cavity
clear area
internal
diaphragm