Symbol 5073 from IEC 60417 - Title/Meaning: Omnidirectional microphone Function/description: To indicate the omnidirectional 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
Own work using: iso.org/obp/graphics/grs/902bb6e5-fa6e-4937-b7da-e6830bd6a124 200.png
Vectorization:  Mrmw