noise of an electret condenser microphone mostly comes from:
1. Impure current source
If the direct current mix with the alternating current signal, we will
hear a stable level, low frequency and continual noise. We can lead the
power to the microphone directly, or set a non-join circuit to filter
the AC signal to improve the situation.
2. The noise from signal
Microphone is a component to receive sound, which can receive wider frequency
range than human ears. Both high and low frequency signal will transform
into noise as a form of harmonic waves after being received. An obvious
example is that the noise happens when the cell phone and the blue tooth
are set too closely. Therefore when we design the microphone circuit,
we should keep it away from the antenna or other components which might
The faulty mechanism design might cause the wind sheer sound or resonant
sound. Normally a deep curved sound hole is good to prevent the ESD, but
it has some bad influence on the sound; for example, it is good for some
frequency but some other frequencies might be declined. Therefore we may
get unnatural sound with buzz or noise.
4. Outer noise
Generally, the main noise is the sound of the wind. The users complain
about the unclear sound because the higher join capacity receives the
sound of the wind or breath. Modifying the join capacity (normally around
0.022~0.1 u) can solve this problem.
On the other hand, if the outer sound (exclude the main sound) is too
louder, it means the sensitivity of the microphone or the loading impedance
is too high, what we can do is change to a low sensitive
microphone or to decrease the loading impedance.
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