Symbol 5074 from IEC 60417 - Title/Meaning: Bi-directional microphone Function/description: To indicate the bi-directional 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/4afc36f3-3019-4871-98ec-169a0a9377e3 200.png
Vectorization:  Mrmw