Le 12/01/2025 à 18:40, aauer1 via groups.io a écrit?:
And there is an MEMS mic called ICS-40800 from TDK with a front and back hole. Regarding the datasheet, it picks up the sound from the front and back side. But mostly ignores the sound from the side (90 degree).
It's a bi-directional microphone, a.k.a. Figure-8.
So, I think this is similar to using 2 omni-directional capsules oriented in the opposite? direction.
No, it's not. Two omnidirectional capsules oriented in whatever direction always result in omnidirectionality.
What you suggest would be two cardioid mics placed back-to-back and wired out-of-phase.
Could be an interesting approach I guess. What do you think?
A figure-8 microphone has the same directivity index as a cardioid (4.8dB), so both placed in diffused field receive the same amount of non-desired signal.
A hypercardioid mic has a directivity index of 6dB, and rejection is optimal at about 110° on both sides. Sounds from the back are attenuated only by 6dB.
It is theoretically the most effective at rejecting ambient noise. However, if the main noise source is at the rear it may be less efficient than a simple cardioid.
