main difference of the appearance between the directional/ noise
canceling and the omni-directional microphone is that the former
one has air holes on the bottom.
The air holes also receive
sound, suppose T1 and P1 mean the time and the pressure when the
front sound hole receives the sound. T2/P2 mean the data when the
back air holes receive the sound. In one word, subtracting these
two data we have the direction of the microphone. Therefore the
unobstructed air holes are very important for the directional or
noise canceling microphone; if the air holes are obstructed, the
characteristic of the microphone will turn to omni-directional.
In the general conference,
we can use the unidirectional microphone to only receive the voice
of the speaker without the clapping from the audience. On the other
hand, in order to record the only sound from the wild bird without
other animals’ sound, we had better choose more professional and
stronger directional microphone.
The noise canceling microphone
is mainly applied to the mechanism that is very close to the speaker,
such as headsets, walky-talky which needs to receive the user’s
voice clearly without any other noise.