Symbol 5075 from IEC 60417 - Title/Meaning: Unidirectional or cardioid microphone Function/description: To indicate the unidirectional characteristic of a microphone.
Additional information: 
The inner symbol, representing the directional pattern, may be used without the enveloping microphone symbol if no ambiguity can arise.
See also symbol 5082
Published in: Supplement C, 1977;First edition, 1973
Own work using: iso.org/obp/graphics/grs/e8cee658-a042-439c-9c44-0b8c0b5ae0aa 200.png
Vectorization:  Mrmw