Some microphones are designed to hear equally in all directions (omnidirectional), and some are designed to be more sensitive in certain directions. Directional microphones can be a big advantage when such a microphone is used in a hearing aid or in an Assistive Listening Device (ALD), because it can be used to enhance some sound that you need to hear (such as speech from someone you are talking with) and to diminish background noise.
Related Journals of Directional Microphone
Transactions on Signal Processing, Transactions on Mechatronics, Microwave and Wireless Components Letters, Transactions on Power Delivery
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